Krish Sadhukhan afb684cb97 KVM: SVM: Don't flush cache if hardware enforces cache coherency across encryption domains
commit e1ebb2b490 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
  eaf78265a4 ("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>
2022-03-16 13:21:48 +01:00
2022-03-11 11:22:39 +01:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
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There are various text files in the Documentation/ subdirectory,
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