KVM: x86: emulate SAHF instruction

Yet another instruction that we fail to emulate, this time found
in Windows 2008R2 32-bit.

Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 8e2a07bd8eac..16c037e7db7d 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3296,6 +3296,18 @@ static int em_cpuid(struct x86_emulate_ctxt *ctxt)
         return X86EMUL_CONTINUE;
 }
 
+static int em_sahf(struct x86_emulate_ctxt *ctxt)
+{
+        u32 flags;
+
+        flags = EFLG_CF | EFLG_PF | EFLG_AF | EFLG_ZF | EFLG_SF;
+        flags &= *reg_rmw(ctxt, VCPU_REGS_RAX) >> 8;
+
+        ctxt->eflags &= ~0xffUL;
+        ctxt->eflags |= flags | X86_EFLAGS_FIXED;
+        return X86EMUL_CONTINUE;
+}
+
 static int em_lahf(struct x86_emulate_ctxt *ctxt)
 {
         *reg_rmw(ctxt, VCPU_REGS_RAX) &= ~0xff00UL;
@@ -3790,7 +3802,8 @@ static const struct opcode opcode_table[256] = {
         D(DstAcc | SrcNone), I(ImplicitOps | SrcAcc, em_cwd),
         I(SrcImmFAddr | No64, em_call_far), N,
         II(ImplicitOps | Stack, em_pushf, pushf),
-        II(ImplicitOps | Stack, em_popf, popf), N, I(ImplicitOps, em_lahf),
+        II(ImplicitOps | Stack, em_popf, popf),
+        I(ImplicitOps, em_sahf), I(ImplicitOps, em_lahf),
         /* 0xA0 - 0xA7 */
         I2bv(DstAcc | SrcMem | Mov | MemAbs, em_mov),
         I2bv(DstMem | SrcAcc | Mov | MemAbs | PageTable, em_mov),