linux-kernel - Re: [PATCH] KVM: selftests: fix irqfd

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Message-ID: <aKy-9eby1OS38uqM@google.com>
Date: Mon, 25 Aug 2025 12:52:21 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sebastian Ott <sebott@...hat.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Shuah Khan <shuah@...nel.org>, Marc Zyngier <maz@...nel.org>, 
	Oliver Upton <oliver.upton@...ux.dev>, kvm@...r.kernel.org, kvmarm@...ts.linux.dev, 
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: selftests: fix irqfd_test on arm64

On Mon, Aug 25, 2025, Sebastian Ott wrote:
> irqfd_test on arm triggers the following assertion:
> ==== Test Assertion Failure ====
>   include/kvm_util.h:527: !ret
>   pid=3643 tid=3643 errno=11 - Resource temporarily unavailable
>      1  0x00000000004026d7: kvm_irqfd at kvm_util.h:527
>      2  0x0000000000402083: main at irqfd_test.c:100
>      3  0x0000ffffa5aab587: ?? ??:0
>      4  0x0000ffffa5aab65f: ?? ??:0
>      5  0x000000000040236f: _start at ??:?
>   KVM_IRQFD failed, rc: -1 errno: 11 (Resource temporarily unavailable)
> 
> Fix this by setting up a vgic for the vm.
> 
> Signed-off-by: Sebastian Ott <sebott@...hat.com>
> ---
> @@ -86,14 +90,30 @@ static void juggle_eventfd_primary(struct kvm_vm *vm, int eventfd)
>  	kvm_irqfd(vm, GSI_BASE_PRIMARY + 1, eventfd, KVM_IRQFD_FLAG_DEASSIGN);
>  }
>  
> +static struct kvm_vm *test_vm_create(void)
> +{
> +#ifdef __aarch64__
> +	struct kvm_vm *vm;
> +	struct kvm_vcpu *vcpu;
> +	int gic_fd;
> +
> +	vm = vm_create_with_one_vcpu(&vcpu, NULL);
> +	gic_fd = vgic_v3_setup(vm, 1, 64);
> +	__TEST_REQUIRE(gic_fd >= 0, "Failed to create vgic-v3");

I don't think this test requires v3+, any GIC will do.

Is there a sane way to handle vGIC creation in kvm_arch_vm_post_create()?  E.g.
could we create a v3 GIC when possible, and fall back to v2?  And then provide a
way for tests to express a hard v3 GIC dependency?

Having to worry about things like this in fairly generic code is quite burdensome.

> +
> +	return vm;
> +#endif
> +	return vm_create(1);
> +}