Re: [PATCH v2] ArmPkg/TimerDxe: remove workaround for KVM timer handling

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On 19 April 2018 at 16:23, Julien Grall <julien.grall@arm.com> wrote:
> Hi Ard,
>
> Sorry for the late reply.
>
> On 19/04/18 09:16, Ard Biesheuvel wrote:
>>
>> On 17 April 2018 at 08:03, Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> wrote:
>>>
>>> When we first ported EDK2 to KVM/arm, we implemented a workaround for
>>> the quirky timer handling on the KVM side. This has been fixed in
>>> Linux commit f120cd6533d2 ("KVM: arm/arm64: timer: Allow the timer to
>>> control the active state") dated 23 June 2014, which was incorporated
>>> into Linux release 4.3.
>>>
>>> So almost 4 years later, it should be safe to drop this workaround on
>>> the EDK2 side.
>>>
>>> This reverts commit b1a633434ddc.
>>>
>>> Cc: cross-distro@lists.linaro.org
>>> Contributed-under: TianoCore Contribution Agreement 1.1
>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>>> Acked-by: Marc Zyngier <marc.zyngier@arm.com>
>>> Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
>>> Acked-by: Laszlo Ersek <lersek@redhat.com>
>>
>>
>> Pushed as 411a373ed6426fb1bff253905b6a59ada44e18ad
>
>
> While this was added for KVM, I believe that code is also needed by Xen.
> Indeed before injecting the interrupt the hypervisor will mask the
> interrupt.
>
> So would it be possible to revert that patch?
>

Given that this is now a Xen-only quirk, I'd rather work around it by
creating a separate ArmGenericTimerCounterLib implementation for Xen.

I will try to put something together beginning of next week.