From: Krish Sadhukhan krish.sadhukhan@oracle.com
commit e1ebb2b49048c4767cfa0d8466f9c701e549fa5e upstream.
In some hardware implementations, coherency between the encrypted and unencrypted mappings of the same physical page in a VM is enforced. In such a system, it is not required for software to flush the VM's page from all CPU caches in the system prior to changing the value of the C-bit for the page.
So check that bit before flushing the cache.
Signed-off-by: Krish Sadhukhan krish.sadhukhan@oracle.com Signed-off-by: Borislav Petkov bp@suse.de Acked-by: Paolo Bonzini pbonzini@redhat.com Link: https://lkml.kernel.org/r/20200917212038.5090-4-krish.sadhukhan@oracle.com [ The linux-5.4.y stable branch does not have the Linux 5.7 refactoring commit eaf78265a4ab ("KVM: SVM: Move SEV code to separate file") so the change was manually applied to sev_clflush_pages() in arch/x86/kvm/svm.c. ] Signed-off-by: Liam Merwick liam.merwick@oracle.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/svm.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1904,7 +1904,8 @@ static void sev_clflush_pages(struct pag uint8_t *page_virtual; unsigned long i;
- if (npages == 0 || pages == NULL) + if (this_cpu_has(X86_FEATURE_SME_COHERENT) || npages == 0 || + pages == NULL) return;
for (i = 0; i < npages; i++) {