[PATCH] KVM: x86: emulate SAHF instruction

From: Paolo Bonzini
Date: Thu Oct 31 2013 - 06:29:57 EST


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

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
Testcase on its way. BTW, lahf/sahf is another candidate for
#UD emulation.

arch/x86/kvm/emulate.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 8e2a07bd8eac..ef750e75c930 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;
@@ -3788,7 +3800,7 @@ static const struct opcode opcode_table[256] = {
DI(SrcAcc | DstReg, pause), X7(D(SrcAcc | DstReg)),
/* 0x98 - 0x9F */
D(DstAcc | SrcNone), I(ImplicitOps | SrcAcc, em_cwd),
- I(SrcImmFAddr | No64, em_call_far), N,
+ I(SrcImmFAddr | No64, em_call_far), I(ImplicitOps, em_sahf),
II(ImplicitOps | Stack, em_pushf, pushf),
II(ImplicitOps | Stack, em_popf, popf), N, I(ImplicitOps, em_lahf),
/* 0xA0 - 0xA7 */
--
1.8.3.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/