Re: [Xen-devel] xc_hvm_inject_trap() races

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 11/02/2016 11:05 AM, Jan Beulich wrote:
>>>> On 02.11.16 at 09:57, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>> On 11/02/2016 10:49 AM, Jan Beulich wrote:
>>> The fact that {vmx,svm}_inject_trap() combine the new exception
>>> with an already injected one (and blindly discard events other than
>>> hw exceptions), otoh, looks like indeed wants to be controllable by
>>> the caller: When the event comes from the outside (the hypercall),
>>> it would clearly seem better to simply tell the caller that no injection
>>> happened and the event needs to be kept pending.
>>
>> However this is not possible with the current design, since all
>> xc_hvm_inject_trap() really does is set the info to be used at
>> hvm_do_resume() time. So at the time xc_hvm_inject_trap() returns, it's
>> not yet possible to know if the injection will succeed or not (assuming
>> we discard it when it would collide with another).
> 
> That's my point - it shouldn't get discarded, but remain latched
> for a future invocation of hvm_do_resume(). Making
> hvm_inject_trap() have a suitable parameter (and a return value)
> would be the easy part of the change here. The difficult part would
> be to make sure the injection context is the right one.

Should I then bring this patch back?

https://lists.xen.org/archives/html/xen-devel/2014-07/msg02927.html

It has been rejected at the time on the grounds that
xc_hvm_inject_trap() is sufficient.


Thanks,
Razvan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel