Re: [PATCH v2 0/3] Change default pointer authentication algorithm on aarch64 to impdef

[Alex Bennée]

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

> On Fri, 10 Jan 2025 at 16:28, Peter Maydell <peter.maydell@linaro.org> wrote:
>>
>> On Thu, 19 Dec 2024 at 18:32, Pierrick Bouvier
>> <pierrick.bouvier@linaro.org> wrote:
>> >
>> > qemu-system-aarch64 default pointer authentication (QARMA5) is expensive, 
>> > we
>> > spent up to 50% of the emulation time running it (when using TCG).
>> >
>> > Switching to pauth-impdef=on is often given as a solution to speed up 
>> > execution.
>> > Thus we talked about making it the new default.
>> >
>> > The first patch introduce a new property (pauth-qarma5) to allow to select
>> > current default algorithm.
>> > The second one change the default.
>> > The third one updates documentation.
>> >
>> > v2:
>> > - ensure we don't break migration compatibility, by using a specific 
>> > backward
>> >   compatible property.
>> > - added some documentation about migration for arm virt machine model.
>>
>> Other than a minor change to the 3rd docs patch which I'll note there:
>> applied to target-arm.next, thanks.
>
> I just noticed that this series breaks 'make check-tcg', because
> the pauth-3 test is explicitly checking the output of the
> pointer-auth operation. I'm going to add in this patch, which
> goes between patches 1 and 2 of this series:
>
> Author: Peter Maydell <peter.maydell@linaro.org>
> Date:   Mon Jan 13 11:42:57 2025 +0000
>
>     tests/tcg/aarch64: force qarma5 for pauth-3 test
>
>     The pauth-3 test explicitly tests that a computation of the
>     pointer-authentication produces the expected result.  This means that
>     it must be run with the QARMA5 algorithm.
>
>     Explicitly set the pauth algorithm when running this test, so that it
>     doesn't break when we change the default algorithm the 'max' CPU
>     uses.
>
>     Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
>
> diff --git a/tests/tcg/aarch64/Makefile.softmmu-target
> b/tests/tcg/aarch64/Makefile.softmmu-target
> index d08d9b01ded..9c52475b7ae 100644
> --- a/tests/tcg/aarch64/Makefile.softmmu-target
> +++ b/tests/tcg/aarch64/Makefile.softmmu-target
> @@ -91,6 +91,9 @@ EXTRA_RUNS+=run-memory-replay
>
>  ifneq ($(CROSS_CC_HAS_ARMV8_3),)
>  pauth-3: CFLAGS += $(CROSS_CC_HAS_ARMV8_3)
> +# This test explicitly checks the output of the pauth operation so we
> +# must force the use of the QARMA5 algorithm for it.
> +run-pauth-3: QEMU_BASE_MACHINE=-M virt -cpu max,pauth-qarma5=on -display none
>  else
>  pauth-3:
>         $(call skip-test, "BUILD of $@", "missing compiler support")
<snip>

Acked-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro