Re: [PATCH] kselftest: kvm/arm64: Skip tests if we can't create a vgic-v3

From: Marc Zyngier <maz@kernel.org>
To: Mark Brown <broonie@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>, James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH] kselftest: kvm/arm64: Skip tests if we can't create a vgic-v3
Date: Wed, 26 Jan 2022 09:07:48 +0000	[thread overview]
Message-ID: <87h79q7tln.wl-maz@kernel.org> (raw)
In-Reply-To: <20220125192851.3907611-1-broonie@kernel.org>

On Tue, 25 Jan 2022 19:28:51 +0000,
Mark Brown <broonie@kernel.org> wrote:
> 
> The arch_timer and vgic_irq kselftests assume that they can create a
> vgic-v3, using the library function vgic_v3_setup() which aborts with a
> test failure if it is not possible to do so. Since vgic-v3 can only be
> instantiated on systems where the host has GICv3 this leads to false
> positives on older systems where that is not the case.
> 
> Fix this by changing vgic_v3_setup() to return an error if the vgic can't
> be instantiated and have the callers skip if this happens. We could also
> exit flagging a skip in vgic_v3_setup() but this would prevent future test
> cases conditionally deciding which GIC to use or generally doing more
> complex output.
> 
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
>  tools/testing/selftests/kvm/aarch64/arch_timer.c | 7 ++++++-
>  tools/testing/selftests/kvm/aarch64/vgic_irq.c   | 5 +++++
>  tools/testing/selftests/kvm/lib/aarch64/vgic.c   | 4 +++-
>  3 files changed, 14 insertions(+), 2 deletions(-)
>

[...]

> diff --git a/tools/testing/selftests/kvm/lib/aarch64/vgic.c b/tools/testing/selftests/kvm/lib/aarch64/vgic.c
> index b3a0fca0d780..647c18733e1b 100644
> --- a/tools/testing/selftests/kvm/lib/aarch64/vgic.c
> +++ b/tools/testing/selftests/kvm/lib/aarch64/vgic.c
> @@ -52,7 +52,9 @@ int vgic_v3_setup(struct kvm_vm *vm, unsigned int nr_vcpus, uint32_t nr_irqs,
>  			nr_vcpus, nr_vcpus_created);
>  
>  	/* Distributor setup */
> -	gic_fd = kvm_create_device(vm, KVM_DEV_TYPE_ARM_VGIC_V3, false);
> +	gic_fd = kvm_create_device(vm, KVM_DEV_TYPE_ARM_VGIC_V3, true);

So you now only test whether it is possible to create a virtual GICv3,
but don't actually create it. How does this work?

	M.

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

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