[v9,6/8] KVM: Update lpage info when private/shared memory are mixed

Message ID 20221025151344.3784230-7-chao.p.peng@linux.intel.com
State New
Headers
Series KVM: mm: fd-based approach for supporting KVM |

Commit Message

Chao Peng Oct. 25, 2022, 3:13 p.m. UTC
  When private/shared memory are mixed in a large page, the lpage_info may
not be accurate and should be updated with this mixed info. A large page
has mixed pages can't be really mapped as large page since its
private/shared pages are from different physical memory.

Update lpage_info when private/shared memory attribute is changed. If
both private and shared pages are within a large page region, it can't
be mapped as large page. It's a bit challenge to track the mixed
info in a 'count' like variable, this patch instead reserves a bit in
'disallow_lpage' to indicate a large page has mixed private/share pages.

Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
---
 arch/x86/include/asm/kvm_host.h |   8 +++
 arch/x86/kvm/mmu/mmu.c          | 112 +++++++++++++++++++++++++++++++-
 arch/x86/kvm/x86.c              |   2 +
 include/linux/kvm_host.h        |  19 ++++++
 virt/kvm/kvm_main.c             |  16 +++--
 5 files changed, 152 insertions(+), 5 deletions(-)
  

Comments

Isaku Yamahata Oct. 26, 2022, 8:46 p.m. UTC | #1
On Tue, Oct 25, 2022 at 11:13:42PM +0800,
Chao Peng <chao.p.peng@linux.intel.com> wrote:

> When private/shared memory are mixed in a large page, the lpage_info may
> not be accurate and should be updated with this mixed info. A large page
> has mixed pages can't be really mapped as large page since its
> private/shared pages are from different physical memory.
> 
> Update lpage_info when private/shared memory attribute is changed. If
> both private and shared pages are within a large page region, it can't
> be mapped as large page. It's a bit challenge to track the mixed
> info in a 'count' like variable, this patch instead reserves a bit in
> 'disallow_lpage' to indicate a large page has mixed private/share pages.
> 
> Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
> ---
>  arch/x86/include/asm/kvm_host.h |   8 +++
>  arch/x86/kvm/mmu/mmu.c          | 112 +++++++++++++++++++++++++++++++-
>  arch/x86/kvm/x86.c              |   2 +
>  include/linux/kvm_host.h        |  19 ++++++
>  virt/kvm/kvm_main.c             |  16 +++--
>  5 files changed, 152 insertions(+), 5 deletions(-)
> 
...
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 33b1aec44fb8..67a9823a8c35 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
...
> @@ -6910,3 +6915,108 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
>  	if (kvm->arch.nx_lpage_recovery_thread)
>  		kthread_stop(kvm->arch.nx_lpage_recovery_thread);
>  }
> +
> +static inline bool linfo_is_mixed(struct kvm_lpage_info *linfo)
> +{
> +	return linfo->disallow_lpage & KVM_LPAGE_PRIVATE_SHARED_MIXED;
> +}
> +
> +static inline void linfo_update_mixed(struct kvm_lpage_info *linfo, bool mixed)
> +{
> +	if (mixed)
> +		linfo->disallow_lpage |= KVM_LPAGE_PRIVATE_SHARED_MIXED;
> +	else
> +		linfo->disallow_lpage &= ~KVM_LPAGE_PRIVATE_SHARED_MIXED;
> +}
> +
> +static bool mem_attr_is_mixed_2m(struct kvm *kvm, unsigned int attr,
> +				 gfn_t start, gfn_t end)
> +{
> +	XA_STATE(xas, &kvm->mem_attr_array, start);
> +	gfn_t gfn = start;
> +	void *entry;
> +	bool shared = attr == KVM_MEM_ATTR_SHARED;
> +	bool mixed = false;
> +
> +	rcu_read_lock();
> +	entry = xas_load(&xas);
> +	while (gfn < end) {
> +		if (xas_retry(&xas, entry))
> +			continue;
> +
> +		KVM_BUG_ON(gfn != xas.xa_index, kvm);
> +
> +		if ((entry && !shared) || (!entry && shared)) {
> +			mixed = true;
> +			goto out;

nitpick: goto isn't needed. break should work.

> +		}
> +
> +		entry = xas_next(&xas);
> +		gfn++;
> +	}
> +out:
> +	rcu_read_unlock();
> +	return mixed;
> +}
> +
> +static bool mem_attr_is_mixed(struct kvm *kvm, struct kvm_memory_slot *slot,
> +			      int level, unsigned int attr,
> +			      gfn_t start, gfn_t end)
> +{
> +	unsigned long gfn;
> +	void *entry;
> +
> +	if (level == PG_LEVEL_2M)
> +		return mem_attr_is_mixed_2m(kvm, attr, start, end);
> +
> +	entry = xa_load(&kvm->mem_attr_array, start);
> +	for (gfn = start; gfn < end; gfn += KVM_PAGES_PER_HPAGE(level - 1)) {
> +		if (linfo_is_mixed(lpage_info_slot(gfn, slot, level - 1)))
> +			return true;
> +		if (xa_load(&kvm->mem_attr_array, gfn) != entry)
> +			return true;
> +	}
> +	return false;
> +}
> +
> +void kvm_arch_update_mem_attr(struct kvm *kvm, struct kvm_memory_slot *slot,
> +			      unsigned int attr, gfn_t start, gfn_t end)
> +{
> +
> +	unsigned long lpage_start, lpage_end;
> +	unsigned long gfn, pages, mask;
> +	int level;
> +
> +	WARN_ONCE(!(attr & (KVM_MEM_ATTR_PRIVATE | KVM_MEM_ATTR_SHARED)),
> +			"Unsupported mem attribute.\n");
> +
> +	/*
> +	 * The sequence matters here: we update the higher level basing on the
> +	 * lower level's scanning result.
> +	 */
> +	for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) {
> +		pages = KVM_PAGES_PER_HPAGE(level);
> +		mask = ~(pages - 1);

nitpick: KVM_HPAGE_MASK(level).  Maybe matter of preference.


> +		lpage_start = max(start & mask, slot->base_gfn);
> +		lpage_end = (end - 1) & mask;
> +
> +		/*
> +		 * We only need to scan the head and tail page, for middle pages
> +		 * we know they are not mixed.
> +		 */
> +		linfo_update_mixed(lpage_info_slot(lpage_start, slot, level),
> +				   mem_attr_is_mixed(kvm, slot, level, attr,
> +						     lpage_start, start));
> +
> +		if (lpage_start == lpage_end)
> +			return;
> +
> +		for (gfn = lpage_start + pages; gfn < lpage_end; gfn += pages)
> +			linfo_update_mixed(lpage_info_slot(gfn, slot, level),
> +					   false);
> +
> +		linfo_update_mixed(lpage_info_slot(lpage_end, slot, level),
> +				   mem_attr_is_mixed(kvm, slot, level, attr,
> +						     end, lpage_end + pages));
> +	}
> +}
  
Chao Peng Oct. 28, 2022, 6:38 a.m. UTC | #2
On Wed, Oct 26, 2022 at 01:46:20PM -0700, Isaku Yamahata wrote:
> On Tue, Oct 25, 2022 at 11:13:42PM +0800,
> Chao Peng <chao.p.peng@linux.intel.com> wrote:
> 
> > When private/shared memory are mixed in a large page, the lpage_info may
> > not be accurate and should be updated with this mixed info. A large page
> > has mixed pages can't be really mapped as large page since its
> > private/shared pages are from different physical memory.
> > 
> > Update lpage_info when private/shared memory attribute is changed. If
> > both private and shared pages are within a large page region, it can't
> > be mapped as large page. It's a bit challenge to track the mixed
> > info in a 'count' like variable, this patch instead reserves a bit in
> > 'disallow_lpage' to indicate a large page has mixed private/share pages.
> > 
> > Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
> > ---
> >  arch/x86/include/asm/kvm_host.h |   8 +++
> >  arch/x86/kvm/mmu/mmu.c          | 112 +++++++++++++++++++++++++++++++-
> >  arch/x86/kvm/x86.c              |   2 +
> >  include/linux/kvm_host.h        |  19 ++++++
> >  virt/kvm/kvm_main.c             |  16 +++--
> >  5 files changed, 152 insertions(+), 5 deletions(-)
> > 
> ...
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index 33b1aec44fb8..67a9823a8c35 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> ...
> > @@ -6910,3 +6915,108 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
> >  	if (kvm->arch.nx_lpage_recovery_thread)
> >  		kthread_stop(kvm->arch.nx_lpage_recovery_thread);
> >  }
> > +
> > +static inline bool linfo_is_mixed(struct kvm_lpage_info *linfo)
> > +{
> > +	return linfo->disallow_lpage & KVM_LPAGE_PRIVATE_SHARED_MIXED;
> > +}
> > +
> > +static inline void linfo_update_mixed(struct kvm_lpage_info *linfo, bool mixed)
> > +{
> > +	if (mixed)
> > +		linfo->disallow_lpage |= KVM_LPAGE_PRIVATE_SHARED_MIXED;
> > +	else
> > +		linfo->disallow_lpage &= ~KVM_LPAGE_PRIVATE_SHARED_MIXED;
> > +}
> > +
> > +static bool mem_attr_is_mixed_2m(struct kvm *kvm, unsigned int attr,
> > +				 gfn_t start, gfn_t end)
> > +{
> > +	XA_STATE(xas, &kvm->mem_attr_array, start);
> > +	gfn_t gfn = start;
> > +	void *entry;
> > +	bool shared = attr == KVM_MEM_ATTR_SHARED;
> > +	bool mixed = false;
> > +
> > +	rcu_read_lock();
> > +	entry = xas_load(&xas);
> > +	while (gfn < end) {
> > +		if (xas_retry(&xas, entry))
> > +			continue;
> > +
> > +		KVM_BUG_ON(gfn != xas.xa_index, kvm);
> > +
> > +		if ((entry && !shared) || (!entry && shared)) {
> > +			mixed = true;
> > +			goto out;
> 
> nitpick: goto isn't needed. break should work.

Thanks.

> 
> > +		}
> > +
> > +		entry = xas_next(&xas);
> > +		gfn++;
> > +	}
> > +out:
> > +	rcu_read_unlock();
> > +	return mixed;
> > +}
> > +
> > +static bool mem_attr_is_mixed(struct kvm *kvm, struct kvm_memory_slot *slot,
> > +			      int level, unsigned int attr,
> > +			      gfn_t start, gfn_t end)
> > +{
> > +	unsigned long gfn;
> > +	void *entry;
> > +
> > +	if (level == PG_LEVEL_2M)
> > +		return mem_attr_is_mixed_2m(kvm, attr, start, end);
> > +
> > +	entry = xa_load(&kvm->mem_attr_array, start);
> > +	for (gfn = start; gfn < end; gfn += KVM_PAGES_PER_HPAGE(level - 1)) {
> > +		if (linfo_is_mixed(lpage_info_slot(gfn, slot, level - 1)))
> > +			return true;
> > +		if (xa_load(&kvm->mem_attr_array, gfn) != entry)
> > +			return true;
> > +	}
> > +	return false;
> > +}
> > +
> > +void kvm_arch_update_mem_attr(struct kvm *kvm, struct kvm_memory_slot *slot,
> > +			      unsigned int attr, gfn_t start, gfn_t end)
> > +{
> > +
> > +	unsigned long lpage_start, lpage_end;
> > +	unsigned long gfn, pages, mask;
> > +	int level;
> > +
> > +	WARN_ONCE(!(attr & (KVM_MEM_ATTR_PRIVATE | KVM_MEM_ATTR_SHARED)),
> > +			"Unsupported mem attribute.\n");
> > +
> > +	/*
> > +	 * The sequence matters here: we update the higher level basing on the
> > +	 * lower level's scanning result.
> > +	 */
> > +	for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) {
> > +		pages = KVM_PAGES_PER_HPAGE(level);
> > +		mask = ~(pages - 1);
> 
> nitpick: KVM_HPAGE_MASK(level).  Maybe matter of preference.

Yes, haven't noticed there is a KVM_HPAGE_MASK defined. Have no
strong preference here, since I already have KVM_PAGES_PER_HPAGE(level),
getting mask is straightforward.

A single KVM_HPAGE_MASK(level) will not give me what I need since here
is gfn, KVM_HPAGE_MASK(level)>> PAGE_SHIFT should be the right
equivalent.

Chao
> 
> 
> > +		lpage_start = max(start & mask, slot->base_gfn);
> > +		lpage_end = (end - 1) & mask;
> > +
> > +		/*
> > +		 * We only need to scan the head and tail page, for middle pages
> > +		 * we know they are not mixed.
> > +		 */
> > +		linfo_update_mixed(lpage_info_slot(lpage_start, slot, level),
> > +				   mem_attr_is_mixed(kvm, slot, level, attr,
> > +						     lpage_start, start));
> > +
> > +		if (lpage_start == lpage_end)
> > +			return;
> > +
> > +		for (gfn = lpage_start + pages; gfn < lpage_end; gfn += pages)
> > +			linfo_update_mixed(lpage_info_slot(gfn, slot, level),
> > +					   false);
> > +
> > +		linfo_update_mixed(lpage_info_slot(lpage_end, slot, level),
> > +				   mem_attr_is_mixed(kvm, slot, level, attr,
> > +						     end, lpage_end + pages));
> > +	}
> > +}
> 
> -- 
> Isaku Yamahata <isaku.yamahata@gmail.com>
  
Yuan Yao Nov. 8, 2022, 12:08 p.m. UTC | #3
On Tue, Oct 25, 2022 at 11:13:42PM +0800, Chao Peng wrote:
> When private/shared memory are mixed in a large page, the lpage_info may
> not be accurate and should be updated with this mixed info. A large page
> has mixed pages can't be really mapped as large page since its
> private/shared pages are from different physical memory.
>
> Update lpage_info when private/shared memory attribute is changed. If
> both private and shared pages are within a large page region, it can't
> be mapped as large page. It's a bit challenge to track the mixed
> info in a 'count' like variable, this patch instead reserves a bit in
> 'disallow_lpage' to indicate a large page has mixed private/share pages.
>
> Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
> ---
>  arch/x86/include/asm/kvm_host.h |   8 +++
>  arch/x86/kvm/mmu/mmu.c          | 112 +++++++++++++++++++++++++++++++-
>  arch/x86/kvm/x86.c              |   2 +
>  include/linux/kvm_host.h        |  19 ++++++
>  virt/kvm/kvm_main.c             |  16 +++--
>  5 files changed, 152 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 7551b6f9c31c..db811a54e3fd 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -37,6 +37,7 @@
>  #include <asm/hyperv-tlfs.h>
>
>  #define __KVM_HAVE_ARCH_VCPU_DEBUGFS
> +#define __KVM_HAVE_ARCH_UPDATE_MEM_ATTR
>
>  #define KVM_MAX_VCPUS 1024
>
> @@ -952,6 +953,13 @@ struct kvm_vcpu_arch {
>  #endif
>  };
>
> +/*
> + * Use a bit in disallow_lpage to indicate private/shared pages mixed at the
> + * level. The remaining bits are used as a reference count.
> + */
> +#define KVM_LPAGE_PRIVATE_SHARED_MIXED		(1U << 31)
> +#define KVM_LPAGE_COUNT_MAX			((1U << 31) - 1)
> +
>  struct kvm_lpage_info {
>  	int disallow_lpage;
>  };
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 33b1aec44fb8..67a9823a8c35 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -762,11 +762,16 @@ static void update_gfn_disallow_lpage_count(const struct kvm_memory_slot *slot,
>  {
>  	struct kvm_lpage_info *linfo;
>  	int i;
> +	int disallow_count;
>
>  	for (i = PG_LEVEL_2M; i <= KVM_MAX_HUGEPAGE_LEVEL; ++i) {
>  		linfo = lpage_info_slot(gfn, slot, i);
> +
> +		disallow_count = linfo->disallow_lpage & KVM_LPAGE_COUNT_MAX;
> +		WARN_ON(disallow_count + count < 0 ||
> +			disallow_count > KVM_LPAGE_COUNT_MAX - count);
> +
>  		linfo->disallow_lpage += count;
> -		WARN_ON(linfo->disallow_lpage < 0);
>  	}
>  }
>
> @@ -6910,3 +6915,108 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
>  	if (kvm->arch.nx_lpage_recovery_thread)
>  		kthread_stop(kvm->arch.nx_lpage_recovery_thread);
>  }
> +
> +static inline bool linfo_is_mixed(struct kvm_lpage_info *linfo)
> +{
> +	return linfo->disallow_lpage & KVM_LPAGE_PRIVATE_SHARED_MIXED;
> +}
> +
> +static inline void linfo_update_mixed(struct kvm_lpage_info *linfo, bool mixed)
> +{
> +	if (mixed)
> +		linfo->disallow_lpage |= KVM_LPAGE_PRIVATE_SHARED_MIXED;
> +	else
> +		linfo->disallow_lpage &= ~KVM_LPAGE_PRIVATE_SHARED_MIXED;
> +}
> +
> +static bool mem_attr_is_mixed_2m(struct kvm *kvm, unsigned int attr,
> +				 gfn_t start, gfn_t end)
> +{
> +	XA_STATE(xas, &kvm->mem_attr_array, start);
> +	gfn_t gfn = start;
> +	void *entry;
> +	bool shared = attr == KVM_MEM_ATTR_SHARED;
> +	bool mixed = false;
> +
> +	rcu_read_lock();
> +	entry = xas_load(&xas);
> +	while (gfn < end) {
> +		if (xas_retry(&xas, entry))
> +			continue;
> +
> +		KVM_BUG_ON(gfn != xas.xa_index, kvm);
> +
> +		if ((entry && !shared) || (!entry && shared)) {
> +			mixed = true;
> +			goto out;
> +		}
> +
> +		entry = xas_next(&xas);
> +		gfn++;
> +	}
> +out:
> +	rcu_read_unlock();
> +	return mixed;
> +}
> +
> +static bool mem_attr_is_mixed(struct kvm *kvm, struct kvm_memory_slot *slot,
> +			      int level, unsigned int attr,
> +			      gfn_t start, gfn_t end)
> +{
> +	unsigned long gfn;
> +	void *entry;
> +
> +	if (level == PG_LEVEL_2M)
> +		return mem_attr_is_mixed_2m(kvm, attr, start, end);
> +
> +	entry = xa_load(&kvm->mem_attr_array, start);
> +	for (gfn = start; gfn < end; gfn += KVM_PAGES_PER_HPAGE(level - 1)) {
> +		if (linfo_is_mixed(lpage_info_slot(gfn, slot, level - 1)))
> +			return true;
> +		if (xa_load(&kvm->mem_attr_array, gfn) != entry)
> +			return true;
> +	}
> +	return false;
> +}
> +
> +void kvm_arch_update_mem_attr(struct kvm *kvm, struct kvm_memory_slot *slot,
> +			      unsigned int attr, gfn_t start, gfn_t end)
> +{
> +
> +	unsigned long lpage_start, lpage_end;
> +	unsigned long gfn, pages, mask;
> +	int level;
> +
> +	WARN_ONCE(!(attr & (KVM_MEM_ATTR_PRIVATE | KVM_MEM_ATTR_SHARED)),
> +			"Unsupported mem attribute.\n");
> +
> +	/*
> +	 * The sequence matters here: we update the higher level basing on the
> +	 * lower level's scanning result.
> +	 */
> +	for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) {
> +		pages = KVM_PAGES_PER_HPAGE(level);
> +		mask = ~(pages - 1);
> +		lpage_start = max(start & mask, slot->base_gfn);
> +		lpage_end = (end - 1) & mask;
> +
> +		/*
> +		 * We only need to scan the head and tail page, for middle pages
> +		 * we know they are not mixed.
> +		 */
> +		linfo_update_mixed(lpage_info_slot(lpage_start, slot, level),
> +				   mem_attr_is_mixed(kvm, slot, level, attr,
> +						     lpage_start, start));

Looks only query the lpage_start, start is not enough:

A and B are private gfns from same lpage_start as below, A > B :
lpage_start
       |---------A
       |----B

Convert A to shared, this makes the upper 2M page to MIX.
Convert B to shared, this also makes the upper 2M page to MIX.
Convert B to private, this makes the upper 2M page to Non-MIX, but
it's incorrect, due to A is shared.

Same to tail case.

> +
> +		if (lpage_start == lpage_end)
> +			return;
> +
> +		for (gfn = lpage_start + pages; gfn < lpage_end; gfn += pages)
> +			linfo_update_mixed(lpage_info_slot(gfn, slot, level),
> +					   false);
> +
> +		linfo_update_mixed(lpage_info_slot(lpage_end, slot, level),
> +				   mem_attr_is_mixed(kvm, slot, level, attr,
> +						     end, lpage_end + pages));
> +	}
> +}
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 02ad31f46dd7..4276ca73bd7b 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -12563,6 +12563,8 @@ static int kvm_alloc_memslot_metadata(struct kvm *kvm,
>  		if ((slot->base_gfn + npages) & (KVM_PAGES_PER_HPAGE(level) - 1))
>  			linfo[lpages - 1].disallow_lpage = 1;
>  		ugfn = slot->userspace_addr >> PAGE_SHIFT;
> +		if (kvm_slot_can_be_private(slot))
> +			ugfn |= slot->restricted_offset >> PAGE_SHIFT;
>  		/*
>  		 * If the gfn and userspace address are not aligned wrt each
>  		 * other, disable large page support for this slot.
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 4ce98fa0153c..6ce36065532c 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2284,4 +2284,23 @@ static inline void kvm_account_pgtable_pages(void *virt, int nr)
>  /* Max number of entries allowed for each kvm dirty ring */
>  #define  KVM_DIRTY_RING_MAX_ENTRIES  65536
>
> +#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
> +
> +#define KVM_MEM_ATTR_SHARED	0x0001
> +#define KVM_MEM_ATTR_PRIVATE	0x0002
> +
> +#ifdef __KVM_HAVE_ARCH_UPDATE_MEM_ATTR
> +void kvm_arch_update_mem_attr(struct kvm *kvm, struct kvm_memory_slot *slot,
> +			      unsigned int attr, gfn_t start, gfn_t end);
> +#else
> +static inline void kvm_arch_update_mem_attr(struct kvm *kvm,
> +					    struct kvm_memory_slot *slot,
> +					    unsigned int attr,
> +					    gfn_t start, gfn_t end)
> +{
> +}
> +#endif
> +
> +#endif /* CONFIG_KVM_GENERIC_PRIVATE_MEM */
> +
>  #endif
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index fc3835826ace..13a37b4d9e97 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -939,7 +939,8 @@ static int kvm_init_mmu_notifier(struct kvm *kvm)
>
>  #ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
>
> -static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end)
> +static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end,
> +				unsigned int attr)
>  {
>  	struct kvm_gfn_range gfn_range;
>  	struct kvm_memory_slot *slot;
> @@ -963,6 +964,7 @@ static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end)
>  			gfn_range.slot = slot;
>
>  			r |= kvm_unmap_gfn_range(kvm, &gfn_range);
> +			kvm_arch_update_mem_attr(kvm, slot, attr, start, end);
>  		}
>  	}
>
> @@ -970,7 +972,6 @@ static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end)
>  		kvm_flush_remote_tlbs(kvm);
>  }
>
> -#define KVM_MEM_ATTR_SHARED	0x0001
>  static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size,
>  				     bool is_private)
>  {
> @@ -979,6 +980,7 @@ static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size,
>  	void *entry;
>  	int idx;
>  	int r = 0;
> +	unsigned int attr;
>
>  	if (size == 0 || gpa + size < gpa)
>  		return -EINVAL;
> @@ -992,7 +994,13 @@ static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size,
>  	 * Guest memory defaults to private, kvm->mem_attr_array only stores
>  	 * shared memory.
>  	 */
> -	entry = is_private ? NULL : xa_mk_value(KVM_MEM_ATTR_SHARED);
> +	if (is_private) {
> +		attr = KVM_MEM_ATTR_PRIVATE;
> +		entry = NULL;
> +	} else {
> +		attr = KVM_MEM_ATTR_SHARED;
> +		entry = xa_mk_value(KVM_MEM_ATTR_SHARED);
> +	}
>
>  	idx = srcu_read_lock(&kvm->srcu);
>  	KVM_MMU_LOCK(kvm);
> @@ -1005,7 +1013,7 @@ static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size,
>  			goto err;
>  	}
>
> -	kvm_unmap_mem_range(kvm, start, end);
> +	kvm_unmap_mem_range(kvm, start, end, attr);
>
>  	goto ret;
>  err:
> --
> 2.25.1
>
  
Chao Peng Nov. 9, 2022, 4:13 a.m. UTC | #4
On Tue, Nov 08, 2022 at 08:08:05PM +0800, Yuan Yao wrote:
> On Tue, Oct 25, 2022 at 11:13:42PM +0800, Chao Peng wrote:
> > When private/shared memory are mixed in a large page, the lpage_info may
> > not be accurate and should be updated with this mixed info. A large page
> > has mixed pages can't be really mapped as large page since its
> > private/shared pages are from different physical memory.
> >
> > Update lpage_info when private/shared memory attribute is changed. If
> > both private and shared pages are within a large page region, it can't
> > be mapped as large page. It's a bit challenge to track the mixed
> > info in a 'count' like variable, this patch instead reserves a bit in
> > 'disallow_lpage' to indicate a large page has mixed private/share pages.
> >
> > Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
> > ---
> >  arch/x86/include/asm/kvm_host.h |   8 +++
> >  arch/x86/kvm/mmu/mmu.c          | 112 +++++++++++++++++++++++++++++++-
> >  arch/x86/kvm/x86.c              |   2 +
> >  include/linux/kvm_host.h        |  19 ++++++
> >  virt/kvm/kvm_main.c             |  16 +++--
> >  5 files changed, 152 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 7551b6f9c31c..db811a54e3fd 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -37,6 +37,7 @@
> >  #include <asm/hyperv-tlfs.h>
> >
> >  #define __KVM_HAVE_ARCH_VCPU_DEBUGFS
> > +#define __KVM_HAVE_ARCH_UPDATE_MEM_ATTR
> >
> >  #define KVM_MAX_VCPUS 1024
> >
> > @@ -952,6 +953,13 @@ struct kvm_vcpu_arch {
> >  #endif
> >  };
> >
> > +/*
> > + * Use a bit in disallow_lpage to indicate private/shared pages mixed at the
> > + * level. The remaining bits are used as a reference count.
> > + */
> > +#define KVM_LPAGE_PRIVATE_SHARED_MIXED		(1U << 31)
> > +#define KVM_LPAGE_COUNT_MAX			((1U << 31) - 1)
> > +
> >  struct kvm_lpage_info {
> >  	int disallow_lpage;
> >  };
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index 33b1aec44fb8..67a9823a8c35 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -762,11 +762,16 @@ static void update_gfn_disallow_lpage_count(const struct kvm_memory_slot *slot,
> >  {
> >  	struct kvm_lpage_info *linfo;
> >  	int i;
> > +	int disallow_count;
> >
> >  	for (i = PG_LEVEL_2M; i <= KVM_MAX_HUGEPAGE_LEVEL; ++i) {
> >  		linfo = lpage_info_slot(gfn, slot, i);
> > +
> > +		disallow_count = linfo->disallow_lpage & KVM_LPAGE_COUNT_MAX;
> > +		WARN_ON(disallow_count + count < 0 ||
> > +			disallow_count > KVM_LPAGE_COUNT_MAX - count);
> > +
> >  		linfo->disallow_lpage += count;
> > -		WARN_ON(linfo->disallow_lpage < 0);
> >  	}
> >  }
> >
> > @@ -6910,3 +6915,108 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
> >  	if (kvm->arch.nx_lpage_recovery_thread)
> >  		kthread_stop(kvm->arch.nx_lpage_recovery_thread);
> >  }
> > +
> > +static inline bool linfo_is_mixed(struct kvm_lpage_info *linfo)
> > +{
> > +	return linfo->disallow_lpage & KVM_LPAGE_PRIVATE_SHARED_MIXED;
> > +}
> > +
> > +static inline void linfo_update_mixed(struct kvm_lpage_info *linfo, bool mixed)
> > +{
> > +	if (mixed)
> > +		linfo->disallow_lpage |= KVM_LPAGE_PRIVATE_SHARED_MIXED;
> > +	else
> > +		linfo->disallow_lpage &= ~KVM_LPAGE_PRIVATE_SHARED_MIXED;
> > +}
> > +
> > +static bool mem_attr_is_mixed_2m(struct kvm *kvm, unsigned int attr,
> > +				 gfn_t start, gfn_t end)
> > +{
> > +	XA_STATE(xas, &kvm->mem_attr_array, start);
> > +	gfn_t gfn = start;
> > +	void *entry;
> > +	bool shared = attr == KVM_MEM_ATTR_SHARED;
> > +	bool mixed = false;
> > +
> > +	rcu_read_lock();
> > +	entry = xas_load(&xas);
> > +	while (gfn < end) {
> > +		if (xas_retry(&xas, entry))
> > +			continue;
> > +
> > +		KVM_BUG_ON(gfn != xas.xa_index, kvm);
> > +
> > +		if ((entry && !shared) || (!entry && shared)) {
> > +			mixed = true;
> > +			goto out;
> > +		}
> > +
> > +		entry = xas_next(&xas);
> > +		gfn++;
> > +	}
> > +out:
> > +	rcu_read_unlock();
> > +	return mixed;
> > +}
> > +
> > +static bool mem_attr_is_mixed(struct kvm *kvm, struct kvm_memory_slot *slot,
> > +			      int level, unsigned int attr,
> > +			      gfn_t start, gfn_t end)
> > +{
> > +	unsigned long gfn;
> > +	void *entry;
> > +
> > +	if (level == PG_LEVEL_2M)
> > +		return mem_attr_is_mixed_2m(kvm, attr, start, end);
> > +
> > +	entry = xa_load(&kvm->mem_attr_array, start);
> > +	for (gfn = start; gfn < end; gfn += KVM_PAGES_PER_HPAGE(level - 1)) {
> > +		if (linfo_is_mixed(lpage_info_slot(gfn, slot, level - 1)))
> > +			return true;
> > +		if (xa_load(&kvm->mem_attr_array, gfn) != entry)
> > +			return true;
> > +	}
> > +	return false;
> > +}
> > +
> > +void kvm_arch_update_mem_attr(struct kvm *kvm, struct kvm_memory_slot *slot,
> > +			      unsigned int attr, gfn_t start, gfn_t end)
> > +{
> > +
> > +	unsigned long lpage_start, lpage_end;
> > +	unsigned long gfn, pages, mask;
> > +	int level;
> > +
> > +	WARN_ONCE(!(attr & (KVM_MEM_ATTR_PRIVATE | KVM_MEM_ATTR_SHARED)),
> > +			"Unsupported mem attribute.\n");
> > +
> > +	/*
> > +	 * The sequence matters here: we update the higher level basing on the
> > +	 * lower level's scanning result.
> > +	 */
> > +	for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) {
> > +		pages = KVM_PAGES_PER_HPAGE(level);
> > +		mask = ~(pages - 1);
> > +		lpage_start = max(start & mask, slot->base_gfn);
> > +		lpage_end = (end - 1) & mask;
> > +
> > +		/*
> > +		 * We only need to scan the head and tail page, for middle pages
> > +		 * we know they are not mixed.
> > +		 */
> > +		linfo_update_mixed(lpage_info_slot(lpage_start, slot, level),
> > +				   mem_attr_is_mixed(kvm, slot, level, attr,
> > +						     lpage_start, start));
> 
> Looks only query the lpage_start, start is not enough:
> 
> A and B are private gfns from same lpage_start as below, A > B :
> lpage_start
>        |---------A
>        |----B
> 
> Convert A to shared, this makes the upper 2M page to MIX.
> Convert B to shared, this also makes the upper 2M page to MIX.
> Convert B to private, this makes the upper 2M page to Non-MIX, but
> it's incorrect, due to A is shared.

In previous versions this is actually "lpage_start, lpage_start +
pages", e.g. covers the whole large page. While fixing another issue[*]
in v8 this was wrongly changed to "lpage_start, start", at that time I
made an assumption that "end > lpage_start + pages" so the remaining
scanning in the same large page is useless if we know what attribute we
will set, this is definitely not true though.

[*]
https://lore.kernel.org/linux-mm/20220930085914.GA2799703@chaop.bj.intel.com/

Thanks,
Chao
> 
> Same to tail case.
> 
> > +
> > +		if (lpage_start == lpage_end)
> > +			return;
> > +
> > +		for (gfn = lpage_start + pages; gfn < lpage_end; gfn += pages)
> > +			linfo_update_mixed(lpage_info_slot(gfn, slot, level),
> > +					   false);
> > +
> > +		linfo_update_mixed(lpage_info_slot(lpage_end, slot, level),
> > +				   mem_attr_is_mixed(kvm, slot, level, attr,
> > +						     end, lpage_end + pages));
> > +	}
> > +}
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 02ad31f46dd7..4276ca73bd7b 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -12563,6 +12563,8 @@ static int kvm_alloc_memslot_metadata(struct kvm *kvm,
> >  		if ((slot->base_gfn + npages) & (KVM_PAGES_PER_HPAGE(level) - 1))
> >  			linfo[lpages - 1].disallow_lpage = 1;
> >  		ugfn = slot->userspace_addr >> PAGE_SHIFT;
> > +		if (kvm_slot_can_be_private(slot))
> > +			ugfn |= slot->restricted_offset >> PAGE_SHIFT;
> >  		/*
> >  		 * If the gfn and userspace address are not aligned wrt each
> >  		 * other, disable large page support for this slot.
> > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> > index 4ce98fa0153c..6ce36065532c 100644
> > --- a/include/linux/kvm_host.h
> > +++ b/include/linux/kvm_host.h
> > @@ -2284,4 +2284,23 @@ static inline void kvm_account_pgtable_pages(void *virt, int nr)
> >  /* Max number of entries allowed for each kvm dirty ring */
> >  #define  KVM_DIRTY_RING_MAX_ENTRIES  65536
> >
> > +#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
> > +
> > +#define KVM_MEM_ATTR_SHARED	0x0001
> > +#define KVM_MEM_ATTR_PRIVATE	0x0002
> > +
> > +#ifdef __KVM_HAVE_ARCH_UPDATE_MEM_ATTR
> > +void kvm_arch_update_mem_attr(struct kvm *kvm, struct kvm_memory_slot *slot,
> > +			      unsigned int attr, gfn_t start, gfn_t end);
> > +#else
> > +static inline void kvm_arch_update_mem_attr(struct kvm *kvm,
> > +					    struct kvm_memory_slot *slot,
> > +					    unsigned int attr,
> > +					    gfn_t start, gfn_t end)
> > +{
> > +}
> > +#endif
> > +
> > +#endif /* CONFIG_KVM_GENERIC_PRIVATE_MEM */
> > +
> >  #endif
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index fc3835826ace..13a37b4d9e97 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -939,7 +939,8 @@ static int kvm_init_mmu_notifier(struct kvm *kvm)
> >
> >  #ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
> >
> > -static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end)
> > +static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end,
> > +				unsigned int attr)
> >  {
> >  	struct kvm_gfn_range gfn_range;
> >  	struct kvm_memory_slot *slot;
> > @@ -963,6 +964,7 @@ static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end)
> >  			gfn_range.slot = slot;
> >
> >  			r |= kvm_unmap_gfn_range(kvm, &gfn_range);
> > +			kvm_arch_update_mem_attr(kvm, slot, attr, start, end);
> >  		}
> >  	}
> >
> > @@ -970,7 +972,6 @@ static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end)
> >  		kvm_flush_remote_tlbs(kvm);
> >  }
> >
> > -#define KVM_MEM_ATTR_SHARED	0x0001
> >  static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size,
> >  				     bool is_private)
> >  {
> > @@ -979,6 +980,7 @@ static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size,
> >  	void *entry;
> >  	int idx;
> >  	int r = 0;
> > +	unsigned int attr;
> >
> >  	if (size == 0 || gpa + size < gpa)
> >  		return -EINVAL;
> > @@ -992,7 +994,13 @@ static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size,
> >  	 * Guest memory defaults to private, kvm->mem_attr_array only stores
> >  	 * shared memory.
> >  	 */
> > -	entry = is_private ? NULL : xa_mk_value(KVM_MEM_ATTR_SHARED);
> > +	if (is_private) {
> > +		attr = KVM_MEM_ATTR_PRIVATE;
> > +		entry = NULL;
> > +	} else {
> > +		attr = KVM_MEM_ATTR_SHARED;
> > +		entry = xa_mk_value(KVM_MEM_ATTR_SHARED);
> > +	}
> >
> >  	idx = srcu_read_lock(&kvm->srcu);
> >  	KVM_MMU_LOCK(kvm);
> > @@ -1005,7 +1013,7 @@ static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size,
> >  			goto err;
> >  	}
> >
> > -	kvm_unmap_mem_range(kvm, start, end);
> > +	kvm_unmap_mem_range(kvm, start, end, attr);
> >
> >  	goto ret;
> >  err:
> > --
> > 2.25.1
> >
  

Patch

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 7551b6f9c31c..db811a54e3fd 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -37,6 +37,7 @@ 
 #include <asm/hyperv-tlfs.h>
 
 #define __KVM_HAVE_ARCH_VCPU_DEBUGFS
+#define __KVM_HAVE_ARCH_UPDATE_MEM_ATTR
 
 #define KVM_MAX_VCPUS 1024
 
@@ -952,6 +953,13 @@  struct kvm_vcpu_arch {
 #endif
 };
 
+/*
+ * Use a bit in disallow_lpage to indicate private/shared pages mixed at the
+ * level. The remaining bits are used as a reference count.
+ */
+#define KVM_LPAGE_PRIVATE_SHARED_MIXED		(1U << 31)
+#define KVM_LPAGE_COUNT_MAX			((1U << 31) - 1)
+
 struct kvm_lpage_info {
 	int disallow_lpage;
 };
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 33b1aec44fb8..67a9823a8c35 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -762,11 +762,16 @@  static void update_gfn_disallow_lpage_count(const struct kvm_memory_slot *slot,
 {
 	struct kvm_lpage_info *linfo;
 	int i;
+	int disallow_count;
 
 	for (i = PG_LEVEL_2M; i <= KVM_MAX_HUGEPAGE_LEVEL; ++i) {
 		linfo = lpage_info_slot(gfn, slot, i);
+
+		disallow_count = linfo->disallow_lpage & KVM_LPAGE_COUNT_MAX;
+		WARN_ON(disallow_count + count < 0 ||
+			disallow_count > KVM_LPAGE_COUNT_MAX - count);
+
 		linfo->disallow_lpage += count;
-		WARN_ON(linfo->disallow_lpage < 0);
 	}
 }
 
@@ -6910,3 +6915,108 @@  void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
 	if (kvm->arch.nx_lpage_recovery_thread)
 		kthread_stop(kvm->arch.nx_lpage_recovery_thread);
 }
+
+static inline bool linfo_is_mixed(struct kvm_lpage_info *linfo)
+{
+	return linfo->disallow_lpage & KVM_LPAGE_PRIVATE_SHARED_MIXED;
+}
+
+static inline void linfo_update_mixed(struct kvm_lpage_info *linfo, bool mixed)
+{
+	if (mixed)
+		linfo->disallow_lpage |= KVM_LPAGE_PRIVATE_SHARED_MIXED;
+	else
+		linfo->disallow_lpage &= ~KVM_LPAGE_PRIVATE_SHARED_MIXED;
+}
+
+static bool mem_attr_is_mixed_2m(struct kvm *kvm, unsigned int attr,
+				 gfn_t start, gfn_t end)
+{
+	XA_STATE(xas, &kvm->mem_attr_array, start);
+	gfn_t gfn = start;
+	void *entry;
+	bool shared = attr == KVM_MEM_ATTR_SHARED;
+	bool mixed = false;
+
+	rcu_read_lock();
+	entry = xas_load(&xas);
+	while (gfn < end) {
+		if (xas_retry(&xas, entry))
+			continue;
+
+		KVM_BUG_ON(gfn != xas.xa_index, kvm);
+
+		if ((entry && !shared) || (!entry && shared)) {
+			mixed = true;
+			goto out;
+		}
+
+		entry = xas_next(&xas);
+		gfn++;
+	}
+out:
+	rcu_read_unlock();
+	return mixed;
+}
+
+static bool mem_attr_is_mixed(struct kvm *kvm, struct kvm_memory_slot *slot,
+			      int level, unsigned int attr,
+			      gfn_t start, gfn_t end)
+{
+	unsigned long gfn;
+	void *entry;
+
+	if (level == PG_LEVEL_2M)
+		return mem_attr_is_mixed_2m(kvm, attr, start, end);
+
+	entry = xa_load(&kvm->mem_attr_array, start);
+	for (gfn = start; gfn < end; gfn += KVM_PAGES_PER_HPAGE(level - 1)) {
+		if (linfo_is_mixed(lpage_info_slot(gfn, slot, level - 1)))
+			return true;
+		if (xa_load(&kvm->mem_attr_array, gfn) != entry)
+			return true;
+	}
+	return false;
+}
+
+void kvm_arch_update_mem_attr(struct kvm *kvm, struct kvm_memory_slot *slot,
+			      unsigned int attr, gfn_t start, gfn_t end)
+{
+
+	unsigned long lpage_start, lpage_end;
+	unsigned long gfn, pages, mask;
+	int level;
+
+	WARN_ONCE(!(attr & (KVM_MEM_ATTR_PRIVATE | KVM_MEM_ATTR_SHARED)),
+			"Unsupported mem attribute.\n");
+
+	/*
+	 * The sequence matters here: we update the higher level basing on the
+	 * lower level's scanning result.
+	 */
+	for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) {
+		pages = KVM_PAGES_PER_HPAGE(level);
+		mask = ~(pages - 1);
+		lpage_start = max(start & mask, slot->base_gfn);
+		lpage_end = (end - 1) & mask;
+
+		/*
+		 * We only need to scan the head and tail page, for middle pages
+		 * we know they are not mixed.
+		 */
+		linfo_update_mixed(lpage_info_slot(lpage_start, slot, level),
+				   mem_attr_is_mixed(kvm, slot, level, attr,
+						     lpage_start, start));
+
+		if (lpage_start == lpage_end)
+			return;
+
+		for (gfn = lpage_start + pages; gfn < lpage_end; gfn += pages)
+			linfo_update_mixed(lpage_info_slot(gfn, slot, level),
+					   false);
+
+		linfo_update_mixed(lpage_info_slot(lpage_end, slot, level),
+				   mem_attr_is_mixed(kvm, slot, level, attr,
+						     end, lpage_end + pages));
+	}
+}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 02ad31f46dd7..4276ca73bd7b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12563,6 +12563,8 @@  static int kvm_alloc_memslot_metadata(struct kvm *kvm,
 		if ((slot->base_gfn + npages) & (KVM_PAGES_PER_HPAGE(level) - 1))
 			linfo[lpages - 1].disallow_lpage = 1;
 		ugfn = slot->userspace_addr >> PAGE_SHIFT;
+		if (kvm_slot_can_be_private(slot))
+			ugfn |= slot->restricted_offset >> PAGE_SHIFT;
 		/*
 		 * If the gfn and userspace address are not aligned wrt each
 		 * other, disable large page support for this slot.
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 4ce98fa0153c..6ce36065532c 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2284,4 +2284,23 @@  static inline void kvm_account_pgtable_pages(void *virt, int nr)
 /* Max number of entries allowed for each kvm dirty ring */
 #define  KVM_DIRTY_RING_MAX_ENTRIES  65536
 
+#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
+
+#define KVM_MEM_ATTR_SHARED	0x0001
+#define KVM_MEM_ATTR_PRIVATE	0x0002
+
+#ifdef __KVM_HAVE_ARCH_UPDATE_MEM_ATTR
+void kvm_arch_update_mem_attr(struct kvm *kvm, struct kvm_memory_slot *slot,
+			      unsigned int attr, gfn_t start, gfn_t end);
+#else
+static inline void kvm_arch_update_mem_attr(struct kvm *kvm,
+					    struct kvm_memory_slot *slot,
+					    unsigned int attr,
+					    gfn_t start, gfn_t end)
+{
+}
+#endif
+
+#endif /* CONFIG_KVM_GENERIC_PRIVATE_MEM */
+
 #endif
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index fc3835826ace..13a37b4d9e97 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -939,7 +939,8 @@  static int kvm_init_mmu_notifier(struct kvm *kvm)
 
 #ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
 
-static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end)
+static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end,
+				unsigned int attr)
 {
 	struct kvm_gfn_range gfn_range;
 	struct kvm_memory_slot *slot;
@@ -963,6 +964,7 @@  static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end)
 			gfn_range.slot = slot;
 
 			r |= kvm_unmap_gfn_range(kvm, &gfn_range);
+			kvm_arch_update_mem_attr(kvm, slot, attr, start, end);
 		}
 	}
 
@@ -970,7 +972,6 @@  static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end)
 		kvm_flush_remote_tlbs(kvm);
 }
 
-#define KVM_MEM_ATTR_SHARED	0x0001
 static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size,
 				     bool is_private)
 {
@@ -979,6 +980,7 @@  static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size,
 	void *entry;
 	int idx;
 	int r = 0;
+	unsigned int attr;
 
 	if (size == 0 || gpa + size < gpa)
 		return -EINVAL;
@@ -992,7 +994,13 @@  static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size,
 	 * Guest memory defaults to private, kvm->mem_attr_array only stores
 	 * shared memory.
 	 */
-	entry = is_private ? NULL : xa_mk_value(KVM_MEM_ATTR_SHARED);
+	if (is_private) {
+		attr = KVM_MEM_ATTR_PRIVATE;
+		entry = NULL;
+	} else {
+		attr = KVM_MEM_ATTR_SHARED;
+		entry = xa_mk_value(KVM_MEM_ATTR_SHARED);
+	}
 
 	idx = srcu_read_lock(&kvm->srcu);
 	KVM_MMU_LOCK(kvm);
@@ -1005,7 +1013,7 @@  static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size,
 			goto err;
 	}
 
-	kvm_unmap_mem_range(kvm, start, end);
+	kvm_unmap_mem_range(kvm, start, end, attr);
 
 	goto ret;
 err: