On 04/12/2011 10:53 AM, Serge E. Hallyn wrote:
Quoting Avi Kivity (avi@xxxxxxxxxx):
> On 04/09/2011 12:09 AM, Serge E. Hallyn wrote:
> >Hi,
> >
> >at https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/747090, it was
> >found that emulate_int_real() sometimes pushes the wrong eip when doing a
> >int. Whereas with non-kvm qemu we push the next instruction after the
> >int, with kvm we push the addr of the instruction itself.
> >
>
>
> The code says:
>
> c->src.val = c->eip;
> emulate_push(ctxt, ops);
> rc = writeback(ctxt, ops);
> if (rc != X86EMUL_CONTINUE)
> return rc;
>
> which appears to be the address of the next instruction from my
> reading of the code (see how insn_fetch() increments c->eip).
Nevertheless removing commits
a92601bb707f6f49fd5563ef3d09928e70cc222e
63995653ade16deacaea5b49ceaf6376314593ac
6e154e56b4d7a6a28c54f0984e13d3f8defc4755
changes the eip value being pushed. If you look at
a92601bb707f6f49fd5563ef3d09928e70cc222e, you see:
if (vmx->rmode.vm86_active) {
- vmx->rmode.irq.pending = true;
- vmx->rmode.irq.vector = nr;
- vmx->rmode.irq.rip = kvm_rip_read(vcpu);
- if (kvm_exception_is_soft(nr))
- vmx->rmode.irq.rip +=
- vmx->vcpu.arch.event_exit_inst_len;
- intr_info |= INTR_TYPE_SOFT_INTR;
- vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr_info);
- vmcs_write32(VM_ENTRY_INSTRUCTION_LEN, 1);
- kvm_rip_write(vcpu, vmx->rmode.irq.rip - 1);
+ if (kvm_inject_realmode_interrupt(vcpu, nr) != EMULATE_DONE)
+ kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
return;
}
but kvm_inject_realmode_interrupt() does not appear to increment
vmx->rmode.irq.rip anywhere, as the code being replaced does.
Ah, I see now. There are two cases, hard interrupt and soft
interrupts. I guess hard interrupts are handled fine, and the failing
case is
guest executes INTn instruction in guest mode
vmx intercepts a page fault (say due to access to the IDT or the stack)
kvm notes that a soft interrupt was in progress (vmx_complete_interrupts)
kvm handles the exception
reinject the interrupt while reentering the guest
so we do need something like
if (soft)
vcpu->arch.emulate_ctxt.eip += inst_len;
in kvm_inject_realmode_interrupt().
--
error compiling committee.c: too many arguments to function
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