Re: [PATCH v7 0/8] target/arm: fully model WFxT instructions for A-profile

["Alex Bennée" <alex.bennee@linaro.org>]

Peter Maydell <peter.maydell@linaro.org> writes:

> On Mon, 8 Jun 2026 at 14:51, Peter Maydell <peter.maydell@linaro.org> wrote:
>>
>> On Fri, 29 May 2026 at 09:29, Alex Bennée <alex.bennee@linaro.org> wrote:
>> >
>> > This series fully models the behaviour of WFxT instructions. We
>> > already had support for WFE for M-profile but we left off A-profile as
>> > it has more potential sources of wake-ups. The main one is the event
>> > stream which includes events from significant bits of the timer
>> > ticking over.
>> >
>> > The refactoring from the previous iterations of the patch have now
>> > been merged.
>> >
>> > I've dropped trying to fully model the global monitor in favour of
>> > taking advantage of the architectural flexibility to have an IMPDEF
>> > event wake up for any reason. We treat the setting of exclusive_addr
>> > as such a reason because it indicates the current vCPU is in a ldstx
>> > exclusive region and we don't want the guest to deadlock. This does mean
>> > the system won't sleep on WFE enabled locks but people shouldn't be
>> > relying on QEMU to model real world sleep patterns anyway given the
>> > efficiency of emulation compared to real HW.
>> >
>> > I've written a test case using kvm-unit-tests:
>> >
>> >   Message-ID: <20260527111822.1563679-1-alex.bennee@linaro.org>
>> >   Date: Wed, 27 May 2026 12:18:21 +0100
>> >   Subject: [kvm-unit-tests PATCH v2] arm: add wfx test case
>> >   From: =?UTF-8?q?Alex=20Benn=C3=A9e?= <alex.bennee@linaro.org>
>> >
>> > All patches are now reviewed.
>>
>>
>>
>> Applied to target-arm.next, thanks.
>
> This turns out to cause failures in "make check-functional": some
> tests now time out. It looks like the patch that triggers this
> is the "enable event stream on WFE instructions".
>
> 13/79 func-thorough+func-arm-thorough+thorough -
> qemu:func-arm-aspeed_rainier               ERROR            36.17s
> exit status 1
> 74/79 func-thorough+func-arm-thorough+thorough -
> qemu:func-arm-smdkc210                     TIMEOUT          90.01s
> killed by signal 15 SIGTERM
> 75/79 func-thorough+func-arm-thorough+thorough - qemu:func-arm-raspi2
>                      TIMEOUT         120.01s   killed by signal 15
> SIGTERM
> 76/79 func-thorough+func-arm-thorough+thorough -
> qemu:func-arm-quanta_gsj                   TIMEOUT         240.01s
> killed by signal 15 SIGTERM
> 77/79 func-thorough+func-arm-thorough+thorough - qemu:func-arm-bpim2u
>                      TIMEOUT         500.01s   killed by signal 15
> SIGTERM
> 78/79 func-thorough+func-arm-thorough+thorough -
> qemu:func-arm-orangepi                     TIMEOUT         540.01s
> killed by signal 15 SIGTERM
> 79/79 func-thorough+func-aarch64-thorough+thorough -
> qemu:func-aarch64-sbsaref_freebsd      TIMEOUT         720.02s
> killed by signal 15 SIGTERM
>
>
> I've kept the first 4 patches, but dropped patches 5-8.
> I also noticed a problem with patch 5 which I've commented on.

OK I'll have a look.

>
> thanks
> -- PMM

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro