On 03/21/2010 04:44 PM, Gleb Natapov wrote:
On Sun, Mar 21, 2010 at 04:41:24PM +0200, Avi Kivity wrote:
On 03/21/2010 01:08 PM, Gleb Natapov wrote:
Decode CMPXCHG8B destination operand in decoding stage. Fixes regression
introduced by "If LOCK prefix is used dest arg should be memory" commit.
This commit relies on dst operand be decoded at the beginning of an
instruction emulation.
@@ -1719,15 +1719,12 @@ static inline int emulate_grp9(struct x86_emulate_ctxt *ctxt,
c->regs[VCPU_REGS_RAX] = (u32) (old>> 0);
c->regs[VCPU_REGS_RDX] = (u32) (old>> 32);
ctxt->eflags&= ~EFLG_ZF;
-
} else {
- new = ((u64)c->regs[VCPU_REGS_RCX]<< 32) |
+ c->dst.val = ((u64)c->regs[VCPU_REGS_RCX]<< 32) |
(u32) c->regs[VCPU_REGS_RBX];
- rc = ops->cmpxchg_emulated(c->modrm_ea,&old,&new, 8, ctxt->vcpu);
- if (rc != X86EMUL_CONTINUE)
- return rc;
ctxt->eflags |= EFLG_ZF;
+ c->lock_prefix = 1;
Why is this bit needed? cmpxchg64b without lock is valid and racy,
but the guest may know it is safe.
Agree. Before this patch cmpxchg8b emulation always called
cmpxchg_emulated(), so to be extra careful I wanted to preserve old
behaviour. Resend the patch without this line?
Better a 3/2 that removes it. So we have a large patch that just
transforms code, and a small patch that corrects an earlier bug. May
help a bisector one day.
--
error compiling committee.c: too many arguments to function
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