KVM: x86: Convert em_salc() to C

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

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Sean Christopherson <seanjc@google.com>
Link: https://lkml.kernel.org/r/20250714103440.634145269@infradead.org

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 390b8a93cd2c7cce0e1599f8de8c687300ca2971..94008cd12f1e34e723266fe4d65b9ff245c42a7e 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -529,11 +529,14 @@ static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop);
        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[256] = {
        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,