Re: [PATCH] hw/intc/arm_gicv3: fix prio masking on pmr write

[Peter Maydell]

On Mon, 14 Nov 2022 at 13:33, Jens Wiklander <jens.wiklander@linaro.org> wrote:
>
> With commit 39f29e599355 ("hw/intc/arm_gicv3: Use correct number of
> priority bits for the CPU") the number of priority bits was changed from
> the maximum value 8 to typically 5. As a consequence a few of the lowest
> bits in ICC_PMR_EL1 becomes RAZ/WI. However prior to this patch one of
> these bits was still used since the supplied priority value is masked
> before it's eventually right shifted with one bit. So the bit is not
> lost as one might expect when the register is read again.
>
> The Linux kernel depends on lowest valid bit to be reset to zero, see
> commit 33625282adaa ("irqchip/gic-v3: Probe for SCR_EL3 being clear
> before resetting AP0Rn") for details.
>
> So fix this by masking the priority value after it may have been right
> shifted by one bit.
>
> Fixes: 39f29e599355 ("hw/intc/arm_gicv3: Use correct number of priority bits 
> for the CPU")
> Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

Thanks for the fix; applied to target-arm.next for 7.2.

> I've only tested this patch on top of v7.1.0 since I couldn't get current
> to run in my test setup.
>
> In case anyone wonders what I'm testing, it's a setup with Hafnium at
> S-EL2, OP-TEE at S-EL1 and the Linux kernel at NS-EL1 (no NS-EL2 for
> simplicity).

Now is a good time to figure out what's not working with current
QEMU, so that if it's a bug in QEMU we can fix it before the
7.2 release. Could you try a bisect of QEMU to see where it broke?
Alternatively, if you have repro instructions and prebuilt image
files I can have a look.

thanks
-- PMM