Re: [kvm-unit-tests PULL 1/2] powerpc: Allow for a custom decr value to be specified to load on decr excp

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On 20/05/2019 08.12, Laurent Vivier wrote:
> On 20/05/2019 06:47, Suraj Jitindar Singh wrote:
>> On Fri, 2019-05-17 at 15:10 +0200, Thomas Huth wrote:
>>> On 17/05/2019 15.03, Laurent Vivier wrote:
>>>> From: Suraj Jitindar Singh <sjitindarsingh@xxxxxxxxx>
>>>>
>>>> Currently the handler for a decrementer exception will simply
>>>> reload the
>>>> maximum value (0x7FFFFFFF), which will take ~4 seconds to expire
>>>> again.
>>>> This means that if a vcpu cedes, it will be ~4 seconds between
>>>> wakeups.
>>>>
>>>> The h_cede_tm test is testing a known breakage when a guest cedes
>>>> while
>>>> suspended. To be sure we cede 500 times to check for the bug.
>>>> However
>>>> since it takes ~4 seconds to be woken up once we've ceded, we only
>>>> get
>>>> through ~20 iterations before we reach the 90 seconds timeout and
>>>> the
>>>> test appears to fail.
>>>>
>>>> Add an option when registering the decrementer handler to specify
>>>> the
>>>> value which should be reloaded by the handler, allowing the timeout
>>>> to be
>>>> chosen.
>>>>
>>>> Modify the spr test to use the max timeout to preserve existing
>>>> behaviour.
>>>> Modify the h_cede_tm test to use a 10ms timeout to ensure we can
>>>> perform
>>>> 500 iterations before hitting the 90 second time limit for a test.
>>>>
>>>> This means the h_cede_tm test now succeeds rather than timing out.
>>>>
>>>> Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@xxxxxxxxx>
>>>> Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
>>>> Reviewed-by: Laurent Vivier <lvivier@xxxxxxxxxx>
>>>> [lv: reset initial value to 0x3FFFFFFF]
>>>
>>> Looks like something went wrong here? There is still the 0x7FFFFFFF
>>> in
>>> the hunk below...
>>
>> No, I think this is correct.
>> Max value is ox7FFFFFFF, but the initial value we load via mtdec is the
>> original 0x3FFFFFFF.
> 
> Yes, that's it.

Ok, since we're only calling H_CEDE once here, we should be fine,
indeed. Sorry for the confusion.

 Thomas



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