From: Sean Christopherson Date: Sat, 8 Jun 2024 00:11:08 +0000 (-0700) Subject: KVM: x86/mmu: Rephrase comment about synthetic PFERR flags in #PF handler X-Git-Tag: v6.11-rc1~89^2~13^2~4 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=caa727882937f0d5260a2a026eb7c27d77404066;p=thirdparty%2Fkernel%2Flinux.git 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 Reviewed-by: Xiaoyao Li Link: https://lore.kernel.org/r/20240608001108.3296879-1-seanjc@google.com Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index fd5378b72896f..46103e3eda306 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4552,7 +4552,10 @@ 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;