KVM: SVM: Flush when freeing encrypted pages even on SME_COHERENT CPUs

KVM: SVM: Flush when freeing encrypted pages even on SME_COHERENT CPUs

commit d54034540a4bd928161a99d2cd25707be06bd78c 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: 02d085e11c00 ("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>