From: Mingwei Zhang mizhang@google.com
commit d45829b351ee6ec5f54dd55e6aca1f44fe239fe6 upstream.
Use clflush_cache_range() to flush the confidential memory when SME_COHERENT is supported in AMD CPU. Cache flush is still needed since SME_COHERENT only support cache invalidation at CPU side. All confidential cache lines are still incoherent with DMA devices.
Cc: stable@vger.kerel.org
Fixes: add5e2f04541 ("KVM: SVM: Add support for the SEV-ES VMSA") Reviewed-by: Sean Christopherson seanjc@google.com Signed-off-by: Mingwei Zhang mizhang@google.com Message-Id: 20220421031407.2516575-3-mizhang@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/svm/sev.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
--- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -1990,11 +1990,14 @@ static void sev_flush_guest_memory(struc unsigned long len) { /* - * If hardware enforced cache coherency for encrypted mappings of the - * same physical page is supported, nothing to do. + * If CPU enforced cache coherency for encrypted mappings of the + * same physical page is supported, use CLFLUSHOPT instead. NOTE: cache + * flush is still needed in order to work properly with DMA devices. */ - if (boot_cpu_has(X86_FEATURE_SME_COHERENT)) + if (boot_cpu_has(X86_FEATURE_SME_COHERENT)) { + clflush_cache_range(va, PAGE_SIZE); return; + }
/* * If the VM Page Flush MSR is supported, use it to flush the page