linux-kernel - [PATCH] KVM: x86: emulate SAHF instruction

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Date:	Thu, 31 Oct 2013 11:29:42 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	kvm@...r.kernel.org, gleb@...hat.com, stable@...r.kernel.org
Subject: [PATCH] KVM: x86: emulate SAHF instruction

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

Cc: stable@...r.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
	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

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