[v4,09/18] x86/sgx: Store struct sgx_encl when allocating new VA pages

  In a later patch, when a cgroup has exceeded the max capacity for EPC
pages, it may need to identify and OOM kill a less active enclave to
make room for other enclaves within the same group. Such a victim
enclave would have no active pages other than the unreclaimable Version
Array (VA) and SECS pages.  Therefore, the cgroup needs examine its
unreclaimable page list, and finding an enclave given a SECS page or a
VA page. This will require a backpointer from a page to an enclave,
which is not available for VA pages.

Because struct sgx_epc_page instances of VA pages are not owned by an
sgx_encl_page instance, mark their owner as sgx_encl: pass the struct
sgx_encl of the enclave allocating the VA page to sgx_alloc_epc_page(),
which will store this value in the owner field of the struct
sgx_epc_page.  In a later patch, VA pages will be placed in an
unreclaimable queue that can be examined by the cgroup to select the OOM
killed enclave.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Signed-off-by: Haitao Huang <haitao.huang@linux.intel.com>
Cc: Sean Christopherson <seanjc@google.com>
---
V4:
- Changes needed for patch reordering
- Revised commit messages (Jarkko)
---
 arch/x86/kernel/cpu/sgx/encl.c  |  5 +++--
 arch/x86/kernel/cpu/sgx/encl.h  |  2 +-
 arch/x86/kernel/cpu/sgx/ioctl.c |  2 +-
 arch/x86/kernel/cpu/sgx/main.c  | 20 ++++++++++----------
 arch/x86/kernel/cpu/sgx/sgx.h   |  5 ++++-
 5 files changed, 19 insertions(+), 15 deletions(-)
  

On Wed Sep 13, 2023 at 7:06 AM EEST, Haitao Huang wrote:
> In a later patch, when a cgroup has exceeded the max capacity for EPC
> pages, it may need to identify and OOM kill a less active enclave to
> make room for other enclaves within the same group. Such a victim
> enclave would have no active pages other than the unreclaimable Version
> Array (VA) and SECS pages.  Therefore, the cgroup needs examine its
> unreclaimable page list, and finding an enclave given a SECS page or a
> VA page. This will require a backpointer from a page to an enclave,
> which is not available for VA pages.
>
> Because struct sgx_epc_page instances of VA pages are not owned by an
> sgx_encl_page instance, mark their owner as sgx_encl: pass the struct
> sgx_encl of the enclave allocating the VA page to sgx_alloc_epc_page(),
> which will store this value in the owner field of the struct
> sgx_epc_page.  In a later patch, VA pages will be placed in an
> unreclaimable queue that can be examined by the cgroup to select the OOM
> killed enclave.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
> Signed-off-by: Haitao Huang <haitao.huang@linux.intel.com>
> Cc: Sean Christopherson <seanjc@google.com>
> ---
> V4:
> - Changes needed for patch reordering
> - Revised commit messages (Jarkko)
> ---
>  arch/x86/kernel/cpu/sgx/encl.c  |  5 +++--
>  arch/x86/kernel/cpu/sgx/encl.h  |  2 +-
>  arch/x86/kernel/cpu/sgx/ioctl.c |  2 +-
>  arch/x86/kernel/cpu/sgx/main.c  | 20 ++++++++++----------
>  arch/x86/kernel/cpu/sgx/sgx.h   |  5 ++++-
>  5 files changed, 19 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
> index d11d4111aa98..1aee0ad00e66 100644
> --- a/arch/x86/kernel/cpu/sgx/encl.c
> +++ b/arch/x86/kernel/cpu/sgx/encl.c
> @@ -1238,6 +1238,7 @@ void sgx_zap_enclave_ptes(struct sgx_encl *encl, unsigned long addr)
>  
>  /**
>   * sgx_alloc_va_page() - Allocate a Version Array (VA) page
> + * @encl:    The enclave that this page is allocated to.

Maybe would more clear:

* @encl:	The new owner of the page

>   * @reclaim: Reclaim EPC pages directly if none available. Enclave
>   *           mutex should not be held if this is set.
>   *
> @@ -1247,12 +1248,12 @@ void sgx_zap_enclave_ptes(struct sgx_encl *encl, unsigned long addr)
>   *   a VA page,
>   *   -errno otherwise
>   */
> -struct sgx_epc_page *sgx_alloc_va_page(bool reclaim)
> +struct sgx_epc_page *sgx_alloc_va_page(struct sgx_encl *encl, bool reclaim)
>  {
>  	struct sgx_epc_page *epc_page;
>  	int ret;
>  
> -	epc_page = sgx_alloc_epc_page(NULL, reclaim);
> +	epc_page = sgx_alloc_epc_page(encl, reclaim);
>  	if (IS_ERR(epc_page))
>  		return ERR_CAST(epc_page);
>  
> diff --git a/arch/x86/kernel/cpu/sgx/encl.h b/arch/x86/kernel/cpu/sgx/encl.h
> index f94ff14c9486..831d63f80f5a 100644
> --- a/arch/x86/kernel/cpu/sgx/encl.h
> +++ b/arch/x86/kernel/cpu/sgx/encl.h
> @@ -116,7 +116,7 @@ struct sgx_encl_page *sgx_encl_page_alloc(struct sgx_encl *encl,
>  					  unsigned long offset,
>  					  u64 secinfo_flags);
>  void sgx_zap_enclave_ptes(struct sgx_encl *encl, unsigned long addr);
> -struct sgx_epc_page *sgx_alloc_va_page(bool reclaim);
> +struct sgx_epc_page *sgx_alloc_va_page(struct sgx_encl *encl, bool reclaim);
>  unsigned int sgx_alloc_va_slot(struct sgx_va_page *va_page);
>  void sgx_free_va_slot(struct sgx_va_page *va_page, unsigned int offset);
>  bool sgx_va_page_full(struct sgx_va_page *va_page);
> diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
> index c28f074d5d71..3ab8c050e665 100644
> --- a/arch/x86/kernel/cpu/sgx/ioctl.c
> +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
> @@ -30,7 +30,7 @@ struct sgx_va_page *sgx_encl_grow(struct sgx_encl *encl, bool reclaim)
>  		if (!va_page)
>  			return ERR_PTR(-ENOMEM);
>  
> -		va_page->epc_page = sgx_alloc_va_page(reclaim);
> +		va_page->epc_page = sgx_alloc_va_page(encl, reclaim);
>  		if (IS_ERR(va_page->epc_page)) {
>  			err = ERR_CAST(va_page->epc_page);
>  			kfree(va_page);
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index fba06dc5abfe..ed813288af44 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -107,7 +107,7 @@ static unsigned long __sgx_sanitize_pages(struct list_head *dirty_page_list)
>  
>  static bool sgx_reclaimer_age(struct sgx_epc_page *epc_page)
>  {
> -	struct sgx_encl_page *page = epc_page->owner;
> +	struct sgx_encl_page *page = epc_page->encl_page;
>  	struct sgx_encl *encl = page->encl;
>  	struct sgx_encl_mm *encl_mm;
>  	bool ret = true;
> @@ -139,7 +139,7 @@ static bool sgx_reclaimer_age(struct sgx_epc_page *epc_page)
>  
>  static void sgx_reclaimer_block(struct sgx_epc_page *epc_page)
>  {
> -	struct sgx_encl_page *page = epc_page->owner;
> +	struct sgx_encl_page *page = epc_page->encl_page;
>  	unsigned long addr = page->desc & PAGE_MASK;
>  	struct sgx_encl *encl = page->encl;
>  	int ret;
> @@ -196,7 +196,7 @@ void sgx_ipi_cb(void *info)
>  static void sgx_encl_ewb(struct sgx_epc_page *epc_page,
>  			 struct sgx_backing *backing)
>  {
> -	struct sgx_encl_page *encl_page = epc_page->owner;
> +	struct sgx_encl_page *encl_page = epc_page->encl_page;
>  	struct sgx_encl *encl = encl_page->encl;
>  	struct sgx_va_page *va_page;
>  	unsigned int va_offset;
> @@ -249,7 +249,7 @@ static void sgx_encl_ewb(struct sgx_epc_page *epc_page,
>  static void sgx_reclaimer_write(struct sgx_epc_page *epc_page,
>  				struct sgx_backing *backing)
>  {
> -	struct sgx_encl_page *encl_page = epc_page->owner;
> +	struct sgx_encl_page *encl_page = epc_page->encl_page;
>  	struct sgx_encl *encl = encl_page->encl;
>  	struct sgx_backing secs_backing;
>  	int ret;
> @@ -309,7 +309,7 @@ static void sgx_reclaim_pages(void)
>  			break;
>  
>  		list_del_init(&epc_page->list);
> -		encl_page = epc_page->owner;
> +		encl_page = epc_page->encl_page;
>  
>  		if (kref_get_unless_zero(&encl_page->encl->refcount) != 0) {
>  			sgx_epc_page_set_state(epc_page, SGX_EPC_PAGE_RECLAIM_IN_PROGRESS);
> @@ -329,7 +329,7 @@ static void sgx_reclaim_pages(void)
>  
>  	i = 0;
>  	list_for_each_entry_safe(epc_page, tmp, &iso, list) {
> -		encl_page = epc_page->owner;
> +		encl_page = epc_page->encl_page;
>  
>  		if (!sgx_reclaimer_age(epc_page))
>  			goto skip;
> @@ -362,7 +362,7 @@ static void sgx_reclaim_pages(void)
>  
>  	i = 0;
>  	list_for_each_entry_safe(epc_page, tmp, &iso, list) {
> -		encl_page = epc_page->owner;
> +		encl_page = epc_page->encl_page;
>  		sgx_reclaimer_write(epc_page, &backing[i++]);
>  
>  		kref_put(&encl_page->encl->refcount, sgx_encl_release);
> @@ -562,7 +562,7 @@ struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim)
>  	for ( ; ; ) {
>  		page = __sgx_alloc_epc_page();
>  		if (!IS_ERR(page)) {
> -			page->owner = owner;
> +			page->encl_page = owner;
>  			break;
>  		}
>  
> @@ -607,7 +607,7 @@ void sgx_free_epc_page(struct sgx_epc_page *page)
>  
>  	spin_lock(&node->lock);
>  
> -	page->owner = NULL;
> +	page->encl_page = NULL;
>  	if (page->poison)
>  		list_add(&page->list, &node->sgx_poison_page_list);
>  	else
> @@ -642,7 +642,7 @@ static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size,
>  	for (i = 0; i < nr_pages; i++) {
>  		section->pages[i].section = index;
>  		section->pages[i].flags = 0;
> -		section->pages[i].owner = NULL;
> +		section->pages[i].encl_page = NULL;
>  		section->pages[i].poison = 0;
>  		list_add_tail(&section->pages[i].list, &sgx_dirty_page_list);
>  	}
> diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
> index 764cec23f4e5..c75ddc7168fa 100644
> --- a/arch/x86/kernel/cpu/sgx/sgx.h
> +++ b/arch/x86/kernel/cpu/sgx/sgx.h
> @@ -68,7 +68,10 @@ struct sgx_epc_page {
>  	unsigned int section;
>  	u16 flags;
>  	u16 poison;
> -	struct sgx_encl_page *owner;

	/* possible owner types */
> +	union {
> +		struct sgx_encl_page *encl_page;
> +		struct sgx_encl *encl;
> +	};
>  	struct list_head list;
>  };
>  
> -- 
> 2.25.1

BR, Jarkko