[kvm-unit-tests PATCH] arm: pmu: Fix failing PMU test when no PMU is available

[kvm-unit-tests PATCH] arm: pmu: Fix failing PMU test when no PMU is available

[Marc Zyngier]

The PMU unit tests fail with an UNDEF exception when no PMU
is available (although KVM hasn't been totally consistent
with that in the past).

This is caused by PMCR_EL0 being read *before* ID_AA64DFR0_EL1
is checked for the PMU version.

Move the PMCR_EL0 access to a reasonable place, which allows the
test to soft-fail gracefully.

Fixes: 784ee933fa5f ("arm: pmu: Introduce defines for PMU versions")
Reported-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arm/pmu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arm/pmu.c b/arm/pmu.c
index cc959e6..15c542a 100644
--- a/arm/pmu.c
+++ b/arm/pmu.c
@@ -988,7 +988,7 @@ static void pmccntr64_test(void)
 /* Return FALSE if no PMU found, otherwise return TRUE */
 static bool pmu_probe(void)
 {
-	uint32_t pmcr = get_pmcr();
+	uint32_t pmcr;
 	uint8_t implementer;
 
 	pmu.version = get_pmu_version();
@@ -997,6 +997,7 @@ static bool pmu_probe(void)
 
 	report_info("PMU version: 0x%x", pmu.version);
 
+	pmcr = get_pmcr();
 	implementer = (pmcr >> PMU_PMCR_IMP_SHIFT) & PMU_PMCR_IMP_MASK;
 	report_info("PMU implementer/ID code: %#"PRIx32"(\"%c\")/%#"PRIx32,
 		    (pmcr >> PMU_PMCR_IMP_SHIFT) & PMU_PMCR_IMP_MASK,
-- 
2.30.0

Re: [kvm-unit-tests PATCH] arm: pmu: Fix failing PMU test when no PMU is available

[Alexandru Elisei]

Hi Marc,

Thank you for the patch! I have already sent a patch for this [1], which was
queued by Drew [2], but apparently has not landed in master yet.

[1] https://www.spinics.net/lists/kvm-arm/msg44084.html
[2]
https://gitlab.com/rhdrjones/kvm-unit-tests/-/commit/241dac4cadfd7d7ace8c8c3f0613376311b4e785


Thanks,

Alex

On 3/24/21 2:38 PM, Marc Zyngier wrote:
> The PMU unit tests fail with an UNDEF exception when no PMU
> is available (although KVM hasn't been totally consistent
> with that in the past).
>
> This is caused by PMCR_EL0 being read *before* ID_AA64DFR0_EL1
> is checked for the PMU version.
>
> Move the PMCR_EL0 access to a reasonable place, which allows the
> test to soft-fail gracefully.
>
> Fixes: 784ee933fa5f ("arm: pmu: Introduce defines for PMU versions")
> Reported-by: Andrew Walbran <qwandor@google.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  arm/pmu.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arm/pmu.c b/arm/pmu.c
> index cc959e6..15c542a 100644
> --- a/arm/pmu.c
> +++ b/arm/pmu.c
> @@ -988,7 +988,7 @@ static void pmccntr64_test(void)
>  /* Return FALSE if no PMU found, otherwise return TRUE */
>  static bool pmu_probe(void)
>  {
> -	uint32_t pmcr = get_pmcr();
> +	uint32_t pmcr;
>  	uint8_t implementer;
>  
>  	pmu.version = get_pmu_version();
> @@ -997,6 +997,7 @@ static bool pmu_probe(void)
>  
>  	report_info("PMU version: 0x%x", pmu.version);
>  
> +	pmcr = get_pmcr();
>  	implementer = (pmcr >> PMU_PMCR_IMP_SHIFT) & PMU_PMCR_IMP_MASK;
>  	report_info("PMU implementer/ID code: %#"PRIx32"(\"%c\")/%#"PRIx32,
>  		    (pmcr >> PMU_PMCR_IMP_SHIFT) & PMU_PMCR_IMP_MASK,

Re: [kvm-unit-tests PATCH] arm: pmu: Fix failing PMU test when no PMU is available

[Andrew Jones]

On Wed, Mar 24, 2021 at 02:50:05PM +0000, Alexandru Elisei wrote:
> Hi Marc,
> 
> Thank you for the patch! I have already sent a patch for this [1], which was
> queued by Drew [2], but apparently has not landed in master yet.
> 
> [1] https://www.spinics.net/lists/kvm-arm/msg44084.html
> [2]
> https://gitlab.com/rhdrjones/kvm-unit-tests/-/commit/241dac4cadfd7d7ace8c8c3f0613376311b4e785

Thanks to you both for the patch and sorry for not getting Alexandru's
patch in early enough to avoid the double reporting and fixing. I
plan to send Paolo an MR as soon as tomorrow that includes the
patch and many others.

Thanks,
drew

Re: [kvm-unit-tests PATCH] arm: pmu: Fix failing PMU test when no PMU is available

[Marc Zyngier]

On Wed, 24 Mar 2021 15:10:58 +0000,
Andrew Jones <drjones@redhat.com> wrote:
> 
> On Wed, Mar 24, 2021 at 02:50:05PM +0000, Alexandru Elisei wrote:
> > Hi Marc,
> > 
> > Thank you for the patch! I have already sent a patch for this [1], which was
> > queued by Drew [2], but apparently has not landed in master yet.
> > 
> > [1] https://www.spinics.net/lists/kvm-arm/msg44084.html
> > [2]
> > https://gitlab.com/rhdrjones/kvm-unit-tests/-/commit/241dac4cadfd7d7ace8c8c3f0613376311b4e785
> 
> Thanks to you both for the patch and sorry for not getting Alexandru's
> patch in early enough to avoid the double reporting and fixing. I
> plan to send Paolo an MR as soon as tomorrow that includes the
> patch and many others.

No worries. Thanks both!

	M.

-- 
Without deviation from the norm, progress is not possible.