[PATCH] KVM: x86: clflushopt should be treated as a no-op by emulation

From: David Edmondson <david.edmondson@oracle.com>
To: linux-kernel@vger.kernel.org
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
	Nadav Amit <namit@cs.technion.ac.il>,
	x86@kernel.org, Wanpeng Li <wanpengli@tencent.com>,
	kvm@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Joerg Roedel <joro@8bytes.org>,
	Jim Mattson <jmattson@google.com>, Borislav Petkov <bp@alien8.de>,
	Ingo Molnar <mingo@redhat.com>,
	David Edmondson <david.edmondson@oracle.com>
Subject: [PATCH] KVM: x86: clflushopt should be treated as a no-op by emulation
Date: Tue,  3 Nov 2020 12:04:00 +0000	[thread overview]
Message-ID: <20201103120400.240882-1-david.edmondson@oracle.com> (raw)

The instruction emulator ignores clflush instructions, yet fails to
support clflushopt. Treat both similarly.

Fixes: 13e457e0eebf ("KVM: x86: Emulator does not decode clflush well")
Signed-off-by: David Edmondson <david.edmondson@oracle.com>
---
 arch/x86/kvm/emulate.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 0d917eb70319..56cae1ff9e3f 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4046,6 +4046,12 @@ static int em_clflush(struct x86_emulate_ctxt *ctxt)
 	return X86EMUL_CONTINUE;
 }
 
+static int em_clflushopt(struct x86_emulate_ctxt *ctxt)
+{
+	/* emulating clflushopt regardless of cpuid */
+	return X86EMUL_CONTINUE;
+}
+
 static int em_movsxd(struct x86_emulate_ctxt *ctxt)
 {
 	ctxt->dst.val = (s32) ctxt->src.val;
@@ -4585,7 +4591,7 @@ static const struct opcode group11[] = {
 };
 
 static const struct gprefix pfx_0f_ae_7 = {
-	I(SrcMem | ByteOp, em_clflush), N, N, N,
+	I(SrcMem | ByteOp, em_clflush), I(SrcMem | ByteOp, em_clflushopt), N, N,
 };
 
 static const struct group_dual group15 = { {
-- 
2.28.0

