linux-kernel - [PATCH v2 09/13] x86/kvm/emulate: Convert em

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Message-ID: <20250430112349.963740147@infradead.org>
Date: Wed, 30 Apr 2025 13:07:43 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: x86@...nel.org
Cc: kys@...rosoft.com,
 haiyangz@...rosoft.com,
 wei.liu@...nel.org,
 decui@...rosoft.com,
 tglx@...utronix.de,
 mingo@...hat.com,
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 dave.hansen@...ux.intel.com,
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 pbonzini@...hat.com,
 ardb@...nel.org,
 kees@...nel.org,
 Arnd Bergmann <arnd@...db.de>,
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 jpoimboe@...nel.org,
 peterz@...radead.org,
 linux-hyperv@...r.kernel.org,
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Subject: [PATCH v2 09/13] x86/kvm/emulate: Convert em_salc() to C

Implement the SALC (Set AL if Carry) instruction in C.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/kvm/emulate.c |   15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -529,11 +529,14 @@ static int fastop(struct x86_emulate_ctx
 	ON64(FOP3E(op##q, rax, rdx, cl)) \
 	FOP_END
 
-FOP_START(salc)
-FOP_FUNC(salc)
-"pushf; sbb %al, %al; popf \n\t"
-FOP_RET(salc)
-FOP_END;
+static int em_salc(struct x86_emulate_ctxt *ctxt)
+{
+	/*
+	 * Set AL 0xFF if CF is set, or 0x00 when clear.
+	 */
+	ctxt->dst.val = 0xFF * !!(ctxt->eflags & X86_EFLAGS_CF);
+	return X86EMUL_CONTINUE;
+}
 
 /*
  * XXX: inoutclob user must know where the argument is being expanded.
@@ -4423,7 +4426,7 @@ static const struct opcode opcode_table[
 	G(Src2CL | ByteOp, group2), G(Src2CL, group2),
 	I(DstAcc | SrcImmUByte | No64, em_aam),
 	I(DstAcc | SrcImmUByte | No64, em_aad),
-	F(DstAcc | ByteOp | No64, em_salc),
+	I(DstAcc | ByteOp | No64, em_salc),
 	I(DstAcc | SrcXLat | ByteOp, em_mov),
 	/* 0xD8 - 0xDF */
 	N, E(0, &escape_d9), N, E(0, &escape_db), N, E(0, &escape_dd), N, N,