[PATCH 2/2] KVM: SVM: Don't flush cache of SEV-encrypted pages if hardware enforces cache coherency across encryption domains

[Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>]

Some hardware implementations may enforce cache coherency across encryption
domains. In such cases, it's not required to flush SEV-encrypted pages off
cache lines.

Signed-off-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
---
 arch/x86/kvm/svm/sev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 402dc4234e39..c8ed8a62d5ef 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -384,7 +384,8 @@ static void sev_clflush_pages(struct page *pages[], unsigned long npages)
 	uint8_t *page_virtual;
 	unsigned long i;
 
-	if (npages == 0 || pages == NULL)
+	if ((cpuid_eax(SVM_SME_CPUID_FUNC) & (1u << 10)) || npages == 0 ||
+	    pages == NULL)
 		return;
 
 	for (i = 0; i < npages; i++) {
-- 
2.18.4