Re: [PATCH 1/4] target/arm: hold bql when SEV sets the event_register

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

Lorand Marton <lorandmarton.dev@gmail.com> writes:

> On Fri, 30 Oct 2026 at 14:10, Alex Bennée <alex.bennee@linaro.org> wrote:
>> There is a race in qemu_process_cpu_events and sleeping on halt_cond
>> where we can miss the setting of the event_register which would cause
>> arm_cpu_has_work to report we shouldn't sleep. As by definition the
>> bql has to be held when we go to sleep against halt_cond guard the
>> kicking of the cpus by the SEV helper with the BQL to ensure things
>> are properly serialised.
>
> I hit this race with a bare-metal test in which two CPUs pass a turn
> back and forth 500000 times with WFE and SEV (virt, -smp 2,
> semihosting).
>
> On master (af1179b406) it hangs in 10 of 10 runs with -cpu max and in
> 10 of 10 with cortex-a72 (no result after 20 s; a passing run takes
> 2 s). A second test, in which a CPU waits in WFE for a broadcast TLBI
> and an SEV, hangs in 23 of 100 runs with cortex-a53.
>
> With this series applied on the same master, the first test passes
> 150 of 150 runs (50 each with max, cortex-a72 and cortex-a53) and the
> second 600 of 600 (200 each).
>
> Tested-by: Lorand Marton <lorandmarton.dev@gmail.com>
>
> The series has no test case now; I can post these two as
> tests/tcg/aarch64/system tests if that helps.

Are they hand written? I did include the test cases pulled from one of
the bugs here:

  20261029161310.2065290-1-alex.bennee@linaro.org

but I suspect the violate the current AI policy.

>
> Thanks,
> Lorand

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro