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Re: [Xen-devel] [PATCH] x86/emulate: Check current->arch.vm_event in hvmemul_virtual_to_linear()

On 04/08/16 00:17, Jan Beulich wrote:
>>>> On 07.04.16 at 19:54, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>> On 04/07/16 20:27, Jan Beulich wrote:
>>>>>> On 07.04.16 at 10:39, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>>>> Theoretically it is possible for mem_access_emulate_each_rep to be
>>>> true even when current->arch.vm_event == NULL, so add an extra
>>>> check to hvmemul_virtual_to_linear().
>>> Mind saying what those theoretical conditions are when this might
>>> happen?
>> This could happen if someone were to call xc_monitor_emulate_each_rep(),
>> but not xc_monitor_enable() (when current->arch.vm_event gets
>> allocated), or after someone called both, but afterwards called
>> xc_monitor_disable() (when current->arch.vm_event gets freed).
> Then wouldn't the correct action be to fail
> xc_monitor_emulate_each_rep() (i.e. whatever hypercall this
> resolves to) when the monitor is not enabled? (You did already
> clarify that the other variant isn't applicable)?

Yes, I think that's better. I'll do that instead.


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