From: Liam Merwick <liam.merwick@oracle.com>
To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org, x86@kernel.org
Cc: pbonzini@redhat.com, bp@alien8.de, thomas.lendacky@amd.com,
brijesh.singh@amd.com, krish.sadhukhan@oracle.com,
liam.merwick@oracle.com
Subject: [PATCH 5.4 4/4] KVM: SVM: Don't flush cache if hardware enforces cache coherency across encryption domains
Date: Fri, 11 Mar 2022 11:29:27 +0000 [thread overview]
Message-ID: <20220311112927.8400-5-liam.merwick@oracle.com> (raw)
In-Reply-To: <20220311112927.8400-1-liam.merwick@oracle.com>
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
Signed-off-by: Liam Merwick <liam.merwick@oracle.com>
Conflicts:
arch/x86/kvm/svm/sev.c
[ 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. ]
---
arch/x86/kvm/svm.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 2f84509f2828..125970286f28 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1904,7 +1904,8 @@ static void sev_clflush_pages(struct page *pages[], unsigned long npages)
uint8_t *page_virtual;
unsigned long i;
- if (npages == 0 || pages == NULL)
+ if (this_cpu_has(X86_FEATURE_SME_COHERENT) || npages == 0 ||
+ pages == NULL)
return;
for (i = 0; i < npages; i++) {
--
2.27.0
next prev parent reply other threads:[~2022-03-11 11:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-11 11:29 [PATCH 5.4 0/4] Backport fixes to avoid SEV guest with 380GB+ memory causing host cpu softhang Liam Merwick
2022-03-11 11:29 ` [PATCH 5.4 1/4] x86/cpufeatures: Mark two free bits in word 3 Liam Merwick
2022-03-11 11:29 ` [PATCH 5.4 2/4] x86/cpu: Add hardware-enforced cache coherency as a CPUID feature Liam Merwick
2022-03-11 11:29 ` [PATCH 5.4 3/4] x86/mm/pat: Don't flush cache if hardware enforces cache coherency across encryption domnains Liam Merwick
2022-03-11 11:29 ` Liam Merwick [this message]
2022-03-14 9:43 ` [PATCH 5.4 0/4] Backport fixes to avoid SEV guest with 380GB+ memory causing host cpu softhang Greg KH
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