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[RFC,16/33] KVM: x86/mmu: Expose R/W/X flags during memory fault exits

Message ID 20231108111806.92604-17-nsaenz@amazon.com
State New
Headers
Series KVM: x86: hyperv: Introduce VSM support |

Commit Message

Nicolas Saenz Julienne Nov. 8, 2023, 11:17 a.m. UTC 
  Include the fault's read, write and execute status when exiting to
user-space.

Signed-off-by: Nicolas Saenz Julienne <nsaenz@amazon.com>
---
 arch/x86/kvm/mmu/mmu.c   | 4 ++--
 include/linux/kvm_host.h | 9 +++++++--
 include/uapi/linux/kvm.h | 6 ++++++
 3 files changed, 15 insertions(+), 4 deletions(-)

Comments

Maxim Levitsky Nov. 28, 2023, 7:36 a.m. UTC | #1 
On Wed, 2023-11-08 at 11:17 +0000, Nicolas Saenz Julienne wrote:
> Include the fault's read, write and execute status when exiting to
> user-space.
> 
> Signed-off-by: Nicolas Saenz Julienne <nsaenz@amazon.com>
> ---
>  arch/x86/kvm/mmu/mmu.c   | 4 ++--
>  include/linux/kvm_host.h | 9 +++++++--
>  include/uapi/linux/kvm.h | 6 ++++++
>  3 files changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 4e02d506cc25..feca077c0210 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4300,8 +4300,8 @@ static inline u8 kvm_max_level_for_order(int order)
>  static void kvm_mmu_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
>  					      struct kvm_page_fault *fault)
>  {
> -	kvm_prepare_memory_fault_exit(vcpu, fault->gfn << PAGE_SHIFT,
> -				      PAGE_SIZE, fault->write, fault->exec,
> +	kvm_prepare_memory_fault_exit(vcpu, fault->gfn << PAGE_SHIFT, PAGE_SIZE,
> +				      fault->write, fault->exec, fault->user,
>  				      fault->is_private);
>  }
>  
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 71e1e8cf8936..631fd532c97a 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2367,14 +2367,19 @@ static inline void kvm_account_pgtable_pages(void *virt, int nr)
>  static inline void kvm_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
>  						 gpa_t gpa, gpa_t size,
>  						 bool is_write, bool is_exec,
> -						 bool is_private)
> +						 bool is_read, bool is_private)

It almost feels like there is a need for a struct to hold all of those parameters.

>  {
>  	vcpu->run->exit_reason = KVM_EXIT_MEMORY_FAULT;
>  	vcpu->run->memory_fault.gpa = gpa;
>  	vcpu->run->memory_fault.size = size;
>  
> -	/* RWX flags are not (yet) defined or communicated to userspace. */
>  	vcpu->run->memory_fault.flags = 0;
> +	if (is_read)
> +		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_READ;
> +	if (is_write)
> +		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_WRITE;
> +	if (is_exec)
> +		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_EXECUTE;
>  	if (is_private)
>  		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_PRIVATE;
>  }
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 03f5c08fd7aa..0ddffb8b0c99 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -533,7 +533,13 @@ struct kvm_run {
>  		} notify;
>  		/* KVM_EXIT_MEMORY_FAULT */
>  		struct {
> +#define KVM_MEMORY_EXIT_FLAG_READ	(1ULL << 0)
> +#define KVM_MEMORY_EXIT_FLAG_WRITE	(1ULL << 1)
> +#define KVM_MEMORY_EXIT_FLAG_EXECUTE	(1ULL << 2)
>  #define KVM_MEMORY_EXIT_FLAG_PRIVATE	(1ULL << 3)
> +#define KVM_MEMORY_EXIT_NO_ACCESS                            \
> +	(KVM_MEMORY_EXIT_FLAG_NR | KVM_MEMORY_EXIT_FLAG_NW | \
> +	 KVM_MEMORY_EXIT_FLAG_NX)
>  			__u64 flags;
>  			__u64 gpa;
>  			__u64 size;


I don't think that KVM_MEMORY_EXIT_FLAG_NR, KVM_MEMORY_EXIT_FLAG_NW, KVM_MEMORY_EXIT_FLAG_NX are defined anywhere.
Also why KVM_MEMORY_EXIT_NO_ACCESS is needed - userspace can infer it from the lack of other access flags.

Best regards,
	Maxim Levitsky
Sean Christopherson Nov. 28, 2023, 4:31 p.m. UTC | #2 
On Tue, Nov 28, 2023, Maxim Levitsky wrote:
> On Wed, 2023-11-08 at 11:17 +0000, Nicolas Saenz Julienne wrote:
> > Include the fault's read, write and execute status when exiting to
> > user-space.
> > 
> > Signed-off-by: Nicolas Saenz Julienne <nsaenz@amazon.com>
> > ---
> >  arch/x86/kvm/mmu/mmu.c   | 4 ++--
> >  include/linux/kvm_host.h | 9 +++++++--
> >  include/uapi/linux/kvm.h | 6 ++++++
> >  3 files changed, 15 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index 4e02d506cc25..feca077c0210 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -4300,8 +4300,8 @@ static inline u8 kvm_max_level_for_order(int order)
> >  static void kvm_mmu_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
> >  					      struct kvm_page_fault *fault)
> >  {
> > -	kvm_prepare_memory_fault_exit(vcpu, fault->gfn << PAGE_SHIFT,
> > -				      PAGE_SIZE, fault->write, fault->exec,
> > +	kvm_prepare_memory_fault_exit(vcpu, fault->gfn << PAGE_SHIFT, PAGE_SIZE,
> > +				      fault->write, fault->exec, fault->user,
> >  				      fault->is_private);
> >  }
> >  
> > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> > index 71e1e8cf8936..631fd532c97a 100644
> > --- a/include/linux/kvm_host.h
> > +++ b/include/linux/kvm_host.h
> > @@ -2367,14 +2367,19 @@ static inline void kvm_account_pgtable_pages(void *virt, int nr)
> >  static inline void kvm_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
> >  						 gpa_t gpa, gpa_t size,
> >  						 bool is_write, bool is_exec,
> > -						 bool is_private)
> > +						 bool is_read, bool is_private)
> 
> It almost feels like there is a need for a struct to hold all of those parameters.

The most obvious solution would be to make "struct kvm_page_fault" common, e.g.
ARM's user_mem_abort() fills RWX booleans just like x86 fills kvm_page_fault.
But I think it's best to wait to do something like that until after Anish's series
lands[*].  That way the conversion can be more of a pure refactoring.

[*] https://lore.kernel.org/all/20231109210325.3806151-1-amoorthy@google.com
diff mbox series

Patch

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 4e02d506cc25..feca077c0210 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4300,8 +4300,8 @@  static inline u8 kvm_max_level_for_order(int order)
 static void kvm_mmu_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
 					      struct kvm_page_fault *fault)
 {
-	kvm_prepare_memory_fault_exit(vcpu, fault->gfn << PAGE_SHIFT,
-				      PAGE_SIZE, fault->write, fault->exec,
+	kvm_prepare_memory_fault_exit(vcpu, fault->gfn << PAGE_SHIFT, PAGE_SIZE,
+				      fault->write, fault->exec, fault->user,
 				      fault->is_private);
 }
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 71e1e8cf8936..631fd532c97a 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2367,14 +2367,19 @@  static inline void kvm_account_pgtable_pages(void *virt, int nr)
 static inline void kvm_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
 						 gpa_t gpa, gpa_t size,
 						 bool is_write, bool is_exec,
-						 bool is_private)
+						 bool is_read, bool is_private)
 {
 	vcpu->run->exit_reason = KVM_EXIT_MEMORY_FAULT;
 	vcpu->run->memory_fault.gpa = gpa;
 	vcpu->run->memory_fault.size = size;
 
-	/* RWX flags are not (yet) defined or communicated to userspace. */
 	vcpu->run->memory_fault.flags = 0;
+	if (is_read)
+		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_READ;
+	if (is_write)
+		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_WRITE;
+	if (is_exec)
+		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_EXECUTE;
 	if (is_private)
 		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_PRIVATE;
 }
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 03f5c08fd7aa..0ddffb8b0c99 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -533,7 +533,13 @@  struct kvm_run {
 		} notify;
 		/* KVM_EXIT_MEMORY_FAULT */
 		struct {
+#define KVM_MEMORY_EXIT_FLAG_READ	(1ULL << 0)
+#define KVM_MEMORY_EXIT_FLAG_WRITE	(1ULL << 1)
+#define KVM_MEMORY_EXIT_FLAG_EXECUTE	(1ULL << 2)
 #define KVM_MEMORY_EXIT_FLAG_PRIVATE	(1ULL << 3)
+#define KVM_MEMORY_EXIT_NO_ACCESS                            \
+	(KVM_MEMORY_EXIT_FLAG_NR | KVM_MEMORY_EXIT_FLAG_NW | \
+	 KVM_MEMORY_EXIT_FLAG_NX)
 			__u64 flags;
 			__u64 gpa;
 			__u64 size;