Re: [Qemu-devel] [PATCH v3 4/9] target-i386: Add infrastructure for reporting TPR MMIO accesses

[Jan Kiszka]

On 2012-02-16 16:21, Avi Kivity wrote:
> On 02/14/2012 05:13 PM, Jan Kiszka wrote:
>> Note that KVM without in-kernel irqchip will report the address after
>> the instruction that triggered a write access. In contrast, read
>> accesses will return the precise information.
>>
> 
> Well this is wierd.  We could retro-doc one or the other behaviour, but
> this-on-read-but-that-on-write is just too strange.
> 
> The documented way of dealing with this is to queue a signal and reenter
> the guest.  kvm will perform anything it needs to complete the
> instruction (perhaps issuing more mmio, say if someone used movsd to
> read the APIC) and then exit on the signal.  By then rip will point
> exactly after the instruction.

Hmm, true. And can trivially be changed (I'm injecting the event after
instruction completion). Will role out a new version.

Jan

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