KVM: x86: cmpxchg emulation should compare in reverse order (37c564f2) · Commits · 戴 / test

The current implementation of cmpxchg does not update the flags correctly, since the accumulator should be compared with the destination and not the other way around. The current implementation does not update the flags correctly. Signed-off-by:

Nadav Amit <namit@cs.technion.ac.il> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/emulate.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -2052,8 +2052,10 @@ static int em_ret_far_imm(struct x86_emulate_ctxt *ctxt)
		static int em_cmpxchg(struct x86_emulate_ctxt *ctxt)
		{
		/* Save real source value, then compare EAX against destination. */
		ctxt->dst.orig_val = ctxt->dst.val;
		ctxt->dst.val = reg_read(ctxt, VCPU_REGS_RAX);
		ctxt->src.orig_val = ctxt->src.val;
		ctxt->src.val = reg_read(ctxt, VCPU_REGS_RAX);
		ctxt->src.val = ctxt->dst.orig_val;
		fastop(ctxt, em_cmp);

		if (ctxt->eflags & EFLG_ZF) {
		@@ -2063,6 +2065,7 @@ static int em_cmpxchg(struct x86_emulate_ctxt *ctxt)
		/* Failure: write the value we saw to EAX. */
		ctxt->dst.type = OP_REG;
		ctxt->dst.addr.reg = reg_rmw(ctxt, VCPU_REGS_RAX);
		ctxt->dst.val = ctxt->dst.orig_val;
		}
		return X86EMUL_CONTINUE;
		}

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