2024-06-08 00:11:22

by Sean Christopherson

Subject: [PATCH] KVM: x86/mmu: Rephrase comment about synthetic PFERR flags in #PF handler

Reword the BUILD_BUG_ON() comment in the legacy #PF handler to explicitly
describe how asserting that synthetic PFERR flags are limited to bits 31:0
protects KVM against inadvertently passing a synthetic flag to the common
page fault handler.

No functional change intended.

Suggested-by: Xiaoyao Li <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
---
arch/x86/kvm/mmu/mmu.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 8d7115230739..2421d971ce1b 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4599,7 +4599,10 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
if (WARN_ON_ONCE(error_code >> 32))
error_code = lower_32_bits(error_code);

- /* Ensure the above sanity check also covers KVM-defined flags. */
+ /*
+ * Restrict KVM-defined flags to bits 63:32 so that it's impossible for
+ * them to conflict with #PF error codes, which are limited to 32 bits.
+ */
BUILD_BUG_ON(lower_32_bits(PFERR_SYNTHETIC_MASK));

vcpu->arch.l1tf_flush_l1d = true;

base-commit: b9adc10edd4e14e66db4f7289a88fdbfa45ae7a8
--
2.45.2.505.gda0bf45e8d-goog

2024-06-12 01:59:55

by Xiaoyao Li

Subject: Re: [PATCH] KVM: x86/mmu: Rephrase comment about synthetic PFERR flags in #PF handler

On 6/8/2024 8:11 AM, Sean Christopherson wrote:
> Reword the BUILD_BUG_ON() comment in the legacy #PF handler to explicitly
> describe how asserting that synthetic PFERR flags are limited to bits 31:0
> protects KVM against inadvertently passing a synthetic flag to the common
> page fault handler.
>
> No functional change intended.
>
> Suggested-by: Xiaoyao Li <[email protected]>
> Signed-off-by: Sean Christopherson <[email protected]>

Reviewed-by: Xiaoyao Li <[email protected]>

> ---
> arch/x86/kvm/mmu/mmu.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 8d7115230739..2421d971ce1b 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4599,7 +4599,10 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
> if (WARN_ON_ONCE(error_code >> 32))
> error_code = lower_32_bits(error_code);
>
> - /* Ensure the above sanity check also covers KVM-defined flags. */
> + /*
> + * Restrict KVM-defined flags to bits 63:32 so that it's impossible for
> + * them to conflict with #PF error codes, which are limited to 32 bits.
> + */
> BUILD_BUG_ON(lower_32_bits(PFERR_SYNTHETIC_MASK));
>
> vcpu->arch.l1tf_flush_l1d = true;
>
> base-commit: b9adc10edd4e14e66db4f7289a88fdbfa45ae7a8

2024-06-15 00:03:45

by Sean Christopherson

Subject: Re: [PATCH] KVM: x86/mmu: Rephrase comment about synthetic PFERR flags in #PF handler

On Fri, 07 Jun 2024 17:11:08 -0700, Sean Christopherson wrote:
> Reword the BUILD_BUG_ON() comment in the legacy #PF handler to explicitly
> describe how asserting that synthetic PFERR flags are limited to bits 31:0
> protects KVM against inadvertently passing a synthetic flag to the common
> page fault handler.
>
> No functional change intended.
>
> [...]

Applied to kvm-x86 mmu, thanks!

[1/1] KVM: x86/mmu: Rephrase comment about synthetic PFERR flags in #PF handler
https://github.com/kvm-x86/linux/commit/caa727882937

--
https://github.com/kvm-x86/linux/tree/next