kvm: svm: Use the hardware provided GPA instead of page walk

When a guest causes a NPF which requires emulation, KVM sometimes walks
the guest page tables to translate the GVA to a GPA. This is unnecessary
most of the time on AMD hardware since the hardware provides the GPA in
EXITINFO2.

The only exception cases involve string operations involving rep or
operations that use two memory locations. With rep, the GPA will only be
the value of the initial NPF and with dual memory locations we won't know
which memory address was translated into EXITINFO2.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 16 insertions, 4 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 56628a44668b..2b8349a2b14b 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -173,6 +173,7 @@
 #define NearBranch  ((u64)1 << 52)  /* Near branches */
 #define No16	    ((u64)1 << 53)  /* No 16 bit operand */
 #define IncSP       ((u64)1 << 54)  /* SP is incremented before ModRM calc */
+#define TwoMemOp    ((u64)1 << 55)  /* Instruction has two memory operand */
 
 #define DstXacc     (DstAccLo | SrcAccHi | SrcWrite)
 
@@ -4256,7 +4257,7 @@ static const struct opcode group1[] = {
 };
 
 static const struct opcode group1A[] = {
-	I(DstMem | SrcNone | Mov | Stack | IncSP, em_pop), N, N, N, N, N, N, N,
+	I(DstMem | SrcNone | Mov | Stack | IncSP | TwoMemOp, em_pop), N, N, N, N, N, N, N,
 };
 
 static const struct opcode group2[] = {
@@ -4294,7 +4295,7 @@ static const struct opcode group5[] = {
 	I(SrcMemFAddr | ImplicitOps,		em_call_far),
 	I(SrcMem | NearBranch,			em_jmp_abs),
 	I(SrcMemFAddr | ImplicitOps,		em_jmp_far),
-	I(SrcMem | Stack,			em_push), D(Undefined),
+	I(SrcMem | Stack | TwoMemOp,		em_push), D(Undefined),
 };
 
 static const struct opcode group6[] = {
@@ -4514,8 +4515,8 @@ static const struct opcode opcode_table[256] = {
 	/* 0xA0 - 0xA7 */
 	I2bv(DstAcc | SrcMem | Mov | MemAbs, em_mov),
 	I2bv(DstMem | SrcAcc | Mov | MemAbs | PageTable, em_mov),
-	I2bv(SrcSI | DstDI | Mov | String, em_mov),
-	F2bv(SrcSI | DstDI | String | NoWrite, em_cmp_r),
+	I2bv(SrcSI | DstDI | Mov | String | TwoMemOp, em_mov),
+	F2bv(SrcSI | DstDI | String | NoWrite | TwoMemOp, em_cmp_r),
 	/* 0xA8 - 0xAF */
 	F2bv(DstAcc | SrcImm | NoWrite, em_test),
 	I2bv(SrcAcc | DstDI | Mov | String, em_mov),
@@ -5629,3 +5630,14 @@ void emulator_writeback_register_cache(struct x86_emulate_ctxt *ctxt)
 {
 	writeback_registers(ctxt);
 }
+
+bool emulator_can_use_gpa(struct x86_emulate_ctxt *ctxt)
+{
+	if (ctxt->rep_prefix && (ctxt->d & String))
+		return false;
+
+	if (ctxt->d & TwoMemOp)
+		return false;
+
+	return true;
+}