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@redhat.com>
---
 tools/testing/selftests/kvm/irqfd_test.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/irqfd_test.c b/tools/testing/selftests/kvm/irqfd_test.c
index 7c301b4c7005..f7b8766e9d42 100644
--- a/tools/testing/selftests/kvm/irqfd_test.c
+++ b/tools/testing/selftests/kvm/irqfd_test.c
@@ -8,7 +8,11 @@
 #include <stdint.h>
 #include <sys/sysinfo.h>
 
+#include "processor.h"
 #include "kvm_util.h"
+#ifdef __aarch64__
+#include "vgic.h"
+#endif
 
 static struct kvm_vm *vm1;
 static struct kvm_vm *vm2;
@@ -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");
+
+	return vm;
+#endif
+	return vm_create(1);
+}
+
 int main(int argc, char *argv[])
 {
 	pthread_t racing_thread;
 	int r, i;
 
 	/* Create "full" VMs, as KVM_IRQFD requires an in-kernel IRQ chip. */
-	vm1 = vm_create(1);
-	vm2 = vm_create(1);
+	vm1 = test_vm_create();
+	vm2 = test_vm_create();
 
 	WRITE_ONCE(__eventfd, kvm_new_eventfd());
 
-- 
2.51.0

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@redhat.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);
> +}

On Mon, 25 Aug 2025 20:52:21 +0100,
Sean Christopherson <seanjc@google.com> wrote:
> 
> 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@redhat.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.

There is no such thing as "any GIC". You need to know what is
available, and ask for something that actually exists. So while the
above is wrong on the ground that this doesn't work on v2 or v5, the
selection has to be explicit.

> 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?

You can ask KVM what's available. Like an actual VMM does. There is no
shortage of examples in the current code base.

And ideally, this should be made an integral part of creating a viable
VM, which the current VM creation hack makes a point in not providing.

	M.

-- 
Jazz isn't dead. It just smells funny.

On Mon, Aug 25, 2025, Marc Zyngier wrote:
> On Mon, 25 Aug 2025 20:52:21 +0100,
> Sean Christopherson <seanjc@google.com> wrote:
> > 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?
> 
> You can ask KVM what's available. Like an actual VMM does. There is no
> shortage of examples in the current code base.

Right, by "sane" I meant: is there a way to instantiate a supported GIC without
making it hard/painful to write tests, and without having to plumb in arm64
specific requirements to common APIs?

E.g. are there tests that use the common vm_create() APIs and rely on NOT having
a GIC?

> And ideally, this should be made an integral part of creating a viable
> VM, which the current VM creation hack makes a point in not providing.

On Mon, Aug 25, 2025 at 02:11:30PM -0700, Sean Christopherson wrote:
> On Mon, Aug 25, 2025, Marc Zyngier wrote:
> > On Mon, 25 Aug 2025 20:52:21 +0100,
> > Sean Christopherson <seanjc@google.com> wrote:
> > > 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?
> > 
> > You can ask KVM what's available. Like an actual VMM does. There is no
> > shortage of examples in the current code base.
> 
> Right, by "sane" I meant: is there a way to instantiate a supported GIC without
> making it hard/painful to write tests, and without having to plumb in arm64
> specific requirements to common APIs?
> 
> E.g. are there tests that use the common vm_create() APIs and rely on NOT having
> a GIC?

Instead of stuffing a GIC in behind vm_create(), I'd rather we have a
specific helper for creating a VM with an irqchip. There's tests in
arm64 that rely on all this generic infrastructure and also need to
select / dimension a GIC appropriately for the test.

The majority of selftests don't even need an irqchip anyway.

Thanks,
Oliver

On Mon, Aug 25, 2025, Oliver Upton wrote:
> On Mon, Aug 25, 2025 at 02:11:30PM -0700, Sean Christopherson wrote:
> > On Mon, Aug 25, 2025, Marc Zyngier wrote:
> > > On Mon, 25 Aug 2025 20:52:21 +0100,
> > > Sean Christopherson <seanjc@google.com> wrote:
> > > > 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?
> > > 
> > > You can ask KVM what's available. Like an actual VMM does. There is no
> > > shortage of examples in the current code base.
> > 
> > Right, by "sane" I meant: is there a way to instantiate a supported GIC without
> > making it hard/painful to write tests, and without having to plumb in arm64
> > specific requirements to common APIs?
> > 
> > E.g. are there tests that use the common vm_create() APIs and rely on NOT having
> > a GIC?
> 
> Instead of stuffing a GIC in behind vm_create(), I'd rather we have a
> specific helper for creating a VM with an irqchip. There's tests in
> arm64 that rely on all this generic infrastructure and also need to
> select / dimension a GIC appropriately for the test.

I've no objection to arm64 providing an API for tests that need a specific GIC
configuration (I think it's a great idea), but I don't think that needs to be
mutually exclusive with having the common APIs instantiate _a_ GIC by default.

What if we use a global flag with thread local storage (because paranoia is
basically free, I think) to communicate that the test wants to create a v3 vGIC?

E.g.

---
static __thread bool vm_wants_custom_vgic;

void kvm_arch_vm_post_create(struct kvm_vm *vm)
{
	if (!vm_wants_custom_vgic) {
		<setup default vgic>
	}
}

struct kvm_vm *vm_create_with_vgic_v3(uint32_t nr_vcpus, void *guest_code,
				      uint32_t nr_irqs, struct kvm_vcpu **vcpus)
{
	TEST_ASSERT(!vm_wants_custom_vgic, "blah blah blah");
	vm_wants_custom_vgic = true;
	vm = vm_create_with_vcpus(nr_vcpus, guest_code, vcpus)
	vm_wants_custom_vgic = false;

	vgic_v3_setup(vm, nr_vcpus, nr_irqs);
}

struct kvm_vm *vm_create_with_one_vcpu_and_vgic_v3(struct kvm_vcpu **vcpu,
						   void *guest_code,
						   uint32_t nr_irqs)
{
	struct kvm_vcpu *vcpus[1];
	struct kvm_vm *vm;

	vm = vm_create_with_vgic_v3(1, guest_code, nr_irqs, vcpus);

	*vcpu = vcpus[0];
	return vm;
}
---

> The majority of selftests don't even need an irqchip anyway.

But it's really, really nice for developers if they can assume a certain level of
configuration is done by the infrastructure, i.e. don't have worry about doing
what is effectively "basic" VM setup.

E.g. x86 selftests creates an IRQCHIP, sets up descriptor tables and exception
handlers, and a handful of other "basic" things, and that has eliminated soooo
much boilerplate code and the associated friction with having to know/discover
that e.g. sending IRQs in a test requires additional setup beyond the obvious
steps like wiring up a handler.

On Tue, Aug 26, 2025 at 11:51:18AM -0700, Sean Christopherson wrote:
> On Mon, Aug 25, 2025, Oliver Upton wrote:
> > The majority of selftests don't even need an irqchip anyway.
> 
> But it's really, really nice for developers if they can assume a certain level of
> configuration is done by the infrastructure, i.e. don't have worry about doing
> what is effectively "basic" VM setup.

The more we pile behind what a "basic" VM configuration is the less
expressive the tests become. Being able to immediately grok the *intent*
of a test from reading it first pass is a very good thing. Otherwise I
need to go figure out what the definition of "basic" means when I need
to write a test and decide if that is compatible with what I'm trying to
do.

vm_create_with_irqchip() is delightfully unambiguous.

> E.g. x86 selftests creates an IRQCHIP, sets up descriptor tables and exception
> handlers, and a handful of other "basic" things, and that has eliminated soooo
> much boilerplate code and the associated friction with having to know/discover
> that e.g. sending IRQs in a test requires additional setup beyond the obvious
> steps like wiring up a handler.

That simply isn't going to happen on arm64. On top of the fact that the
irqchip configuration depends on the intent of the test (e.g. wired IRQs
v. MSIs), there's a bunch of guest-side initialization that needs to
happen too.

We can add an extremely barebones GIC when asked for (although guest
init isn't addressed) but batteries are not included on this architecture
and I'd rather not attempt to abstract that.

Thanks,
Oliver

On Tue, Aug 26, 2025, Oliver Upton wrote:
> On Tue, Aug 26, 2025 at 11:51:18AM -0700, Sean Christopherson wrote:
> > On Mon, Aug 25, 2025, Oliver Upton wrote:
> > > The majority of selftests don't even need an irqchip anyway.
> > 
> > But it's really, really nice for developers if they can assume a certain level of
> > configuration is done by the infrastructure, i.e. don't have worry about doing
> > what is effectively "basic" VM setup.
> 
> The more we pile behind what a "basic" VM configuration is the less
> expressive the tests become. Being able to immediately grok the *intent*
> of a test from reading it first pass is a very good thing. Otherwise I
> need to go figure out what the definition of "basic" means when I need
> to write a test and decide if that is compatible with what I'm trying to
> do.

Eh, I don't buy that argument, not as a blanket statement.

The existence of code doesn't always communicate intent, e.g. the _only_ instance
I can think of where doing more setup by default caused problems was a few crusty
x86 tests that relied on an int3 to cause SHUTDOWN due to lack of an IDT.  OMG was
I increduluous when I figured out what those tests were doing.

And in that case, _not_ doing the "basic" setup hid the intent of the test.  Aside
from the fact that deliberately triggering SHUTDOWN was completely unnecessary in
those tests, IMO forcing such a test to use vm_create_barebones() would better
capture that the test is doing something odd, i.e. has unusual intent.

And explicitly doing something doesn't necessarily communicate the intent of the
test.  E.g. the intent of the irqfd_test is to verify that KVM_IRQFD assign and
deassign behaves as expected.  The test never generates IRQs, i.e. doesn't actually
need an IRQCHIP beyond satisfying KVM's requirements for KVM_IRQFD.

There are undoubtedly other tests that have similar "intent".  E.g. the in-progress
mediated PMU support for x86 requires an in-kernel local APIC, and so tests like
pmu_counters_test.c, pmu_event_filter_test.c, and vmx_pmu_caps_test.c will need
to instantiate an IRQCHIP.  None of those tests actually touch the local APIC in
any way, e.g. don't generate PMU interrupts, so creating an IRQCHIP is once again
nothing more than a means to an end, and not indicative of the test's main intent.

I think the use of vgic_v3_setup() in dirty_log_perf_test.c is also a case where
the existence of code fails to communicate intent.  Without the comment in
arch_setup_vm() to explain that having GICv3 somehow reduces the number of exits,
I would be very confused as to why the test cares about GICv3.

I agree there's a balance to be had in terms of doing too much.  Unfortunately in
this case, it sounds like the fundamental problem is that the balance is simply
different for x86 versus arm64.  Having an in-kernel local APIC is tables stakes
for x86, to the point where I'm looking for any excuse to have KVM create a local
APIC by default.  But for arm64, there's tremendous value in having tests do the
lifting.

> vm_create_with_irqchip() is delightfully unambiguous.
>
> > E.g. x86 selftests creates an IRQCHIP, sets up descriptor tables and exception
> > handlers, and a handful of other "basic" things, and that has eliminated soooo
> > much boilerplate code and the associated friction with having to know/discover
> > that e.g. sending IRQs in a test requires additional setup beyond the obvious
> > steps like wiring up a handler.
> 
> That simply isn't going to happen on arm64. On top of the fact that the
> irqchip configuration depends on the intent of the test (e.g. wired IRQs
> v. MSIs), there's a bunch of guest-side initialization that needs to
> happen too.
> 
> We can add an extremely barebones GIC when asked for (although guest
> init isn't addressed) but batteries are not included on this architecture
> and I'd rather not attempt to abstract that.

What about providing an API to do exactly that, instantiate and initialize a
barebones GIC?  E.g.

	void kvm_arch_init_barebones_irqchip(struct kvm_vm *vm)

Hmm, then we'd also need

	void kvm_arch_vm_free(struct kvm_vm *vm)

to gracefully free the GIC, as done by dirty_log_perf_test.c.  Blech.  Though
maybe we'll end up with that hook sooner or later?

All in all, I have no strong preference at this point.

+Naresh

On Tue, Aug 26, 2025, Sean Christopherson wrote:
> On Tue, Aug 26, 2025, Oliver Upton wrote:
> > On Tue, Aug 26, 2025 at 11:51:18AM -0700, Sean Christopherson wrote:
> > > On Mon, Aug 25, 2025, Oliver Upton wrote:
> > > > The majority of selftests don't even need an irqchip anyway.
> > > 
> > > But it's really, really nice for developers if they can assume a certain level of
> > > configuration is done by the infrastructure, i.e. don't have worry about doing
> > > what is effectively "basic" VM setup.
> > 
> > The more we pile behind what a "basic" VM configuration is the less
> > expressive the tests become. Being able to immediately grok the *intent*
> > of a test from reading it first pass is a very good thing. Otherwise I
> > need to go figure out what the definition of "basic" means when I need
> > to write a test and decide if that is compatible with what I'm trying to
> > do.
> 
> Eh, I don't buy that argument, not as a blanket statement.
> 
> The existence of code doesn't always communicate intent, e.g. the _only_ instance
> I can think of where doing more setup by default caused problems was a few crusty
> x86 tests that relied on an int3 to cause SHUTDOWN due to lack of an IDT.  OMG was
> I increduluous when I figured out what those tests were doing.
> 
> And in that case, _not_ doing the "basic" setup hid the intent of the test.  Aside
> from the fact that deliberately triggering SHUTDOWN was completely unnecessary in
> those tests, IMO forcing such a test to use vm_create_barebones() would better
> capture that the test is doing something odd, i.e. has unusual intent.
> 
> And explicitly doing something doesn't necessarily communicate the intent of the
> test.  E.g. the intent of the irqfd_test is to verify that KVM_IRQFD assign and
> deassign behaves as expected.  The test never generates IRQs, i.e. doesn't actually
> need an IRQCHIP beyond satisfying KVM's requirements for KVM_IRQFD.
> 
> There are undoubtedly other tests that have similar "intent".  E.g. the in-progress
> mediated PMU support for x86 requires an in-kernel local APIC, and so tests like
> pmu_counters_test.c, pmu_event_filter_test.c, and vmx_pmu_caps_test.c will need
> to instantiate an IRQCHIP.  None of those tests actually touch the local APIC in
> any way, e.g. don't generate PMU interrupts, so creating an IRQCHIP is once again
> nothing more than a means to an end, and not indicative of the test's main intent.
> 
> I think the use of vgic_v3_setup() in dirty_log_perf_test.c is also a case where
> the existence of code fails to communicate intent.  Without the comment in
> arch_setup_vm() to explain that having GICv3 somehow reduces the number of exits,
> I would be very confused as to why the test cares about GICv3.
> 
> I agree there's a balance to be had in terms of doing too much.  Unfortunately in
> this case, it sounds like the fundamental problem is that the balance is simply
> different for x86 versus arm64.  Having an in-kernel local APIC is tables stakes
> for x86, to the point where I'm looking for any excuse to have KVM create a local
> APIC by default.  But for arm64, there's tremendous value in having tests do the
> lifting.
> 
> > vm_create_with_irqchip() is delightfully unambiguous.
> >
> > > E.g. x86 selftests creates an IRQCHIP, sets up descriptor tables and exception
> > > handlers, and a handful of other "basic" things, and that has eliminated soooo
> > > much boilerplate code and the associated friction with having to know/discover
> > > that e.g. sending IRQs in a test requires additional setup beyond the obvious
> > > steps like wiring up a handler.
> > 
> > That simply isn't going to happen on arm64. On top of the fact that the
> > irqchip configuration depends on the intent of the test (e.g. wired IRQs
> > v. MSIs), there's a bunch of guest-side initialization that needs to
> > happen too.
> > 
> > We can add an extremely barebones GIC when asked for (although guest
> > init isn't addressed) but batteries are not included on this architecture
> > and I'd rather not attempt to abstract that.
> 
> What about providing an API to do exactly that, instantiate and initialize a
> barebones GIC?  E.g.
> 
> 	void kvm_arch_init_barebones_irqchip(struct kvm_vm *vm)
> 
> Hmm, then we'd also need
> 
> 	void kvm_arch_vm_free(struct kvm_vm *vm)
> 
> to gracefully free the GIC, as done by dirty_log_perf_test.c.  Blech.  Though
> maybe we'll end up with that hook sooner or later?
> 
> All in all, I have no strong preference at this point.

Oliver, any thoughts?  This is causing noise in people's CIs, i.e. we should land
a fix sooner than later, even if it's not the "final" form.

On Tue, Sep 30, 2025 at 08:14:19AM -0700, Sean Christopherson wrote:
> > What about providing an API to do exactly that, instantiate and initialize a
> > barebones GIC?  E.g.
> > 
> > 	void kvm_arch_init_barebones_irqchip(struct kvm_vm *vm)
> > 
> > Hmm, then we'd also need
> > 
> > 	void kvm_arch_vm_free(struct kvm_vm *vm)
> > 
> > to gracefully free the GIC, as done by dirty_log_perf_test.c.  Blech.  Though
> > maybe we'll end up with that hook sooner or later?
> > 
> > All in all, I have no strong preference at this point.
> 
> Oliver, any thoughts?  This is causing noise in people's CIs, i.e. we should land
> a fix sooner than later, even if it's not the "final" form. 

The lack of a default VGICv3 wound up getting in my way with some
changes to promote selftests to run in VHE EL2, cc'ed you on that series
since I wound up walking back my gripes here :)

  https://lore.kernel.org/kvmarm/20250917212044.294760-1-oliver.upton@linux.dev/a

That's now in Paolo's tree as of this morning. With that said, I think
irqfd_test needs a bit more attention (below).

Thanks,
Oliver

From 4d0a035fb7e6cead74af4edb24fbcfdec076d321 Mon Sep 17 00:00:00 2001
From: Oliver Upton <oliver.upton@linux.dev>
Date: Tue, 30 Sep 2025 10:53:14 -0700
Subject: [PATCH] KVM: selftests: Fix irqfd_test for non-x86 architectures

The KVM_IRQFD ioctl fails if no irqchip is present in-kernel, which
isn't too surprising as there's not much KVM can do for an IRQ if it
cannot resolve a destination.

As written the irqfd_test assumes that a 'default' VM created in
selftests has an in-kernel irqchip created implicitly. That may be the
case on x86 but it isn't necessarily true on other architectures.

Add an arch predicate indicating if 'default' VMs get an irqchip and
make the irqfd_test depend on it. Work around arm64 VGIC initialization
requirements by using vm_create_with_one_vcpu(), ignoring the created
vCPU as it isn't used for the test.

Fixes: 7e9b231c402a ("KVM: selftests: Add a KVM_IRQFD test to verify uniqueness requirements")
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
 tools/testing/selftests/kvm/include/kvm_util.h    |  2 ++
 tools/testing/selftests/kvm/irqfd_test.c          | 14 +++++++++++---
 tools/testing/selftests/kvm/lib/arm64/processor.c |  5 +++++
 tools/testing/selftests/kvm/lib/kvm_util.c        |  5 +++++
 tools/testing/selftests/kvm/lib/s390/processor.c  |  5 +++++
 tools/testing/selftests/kvm/lib/x86/processor.c   |  5 +++++
 6 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 11b6c5aa3f12..8f23362f59fa 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -1268,4 +1268,6 @@ bool vm_is_gpa_protected(struct kvm_vm *vm, vm_paddr_t paddr);
 
 uint32_t guest_get_vcpuid(void);
 
+bool kvm_arch_has_default_irqchip(void);
+
 #endif /* SELFTEST_KVM_UTIL_H */
diff --git a/tools/testing/selftests/kvm/irqfd_test.c b/tools/testing/selftests/kvm/irqfd_test.c
index 7c301b4c7005..5d7590d01868 100644
--- a/tools/testing/selftests/kvm/irqfd_test.c
+++ b/tools/testing/selftests/kvm/irqfd_test.c
@@ -89,11 +89,19 @@ static void juggle_eventfd_primary(struct kvm_vm *vm, int eventfd)
 int main(int argc, char *argv[])
 {
 	pthread_t racing_thread;
+	struct kvm_vcpu *unused;
 	int r, i;
 
-	/* Create "full" VMs, as KVM_IRQFD requires an in-kernel IRQ chip. */
-	vm1 = vm_create(1);
-	vm2 = vm_create(1);
+	TEST_REQUIRE(kvm_arch_has_default_irqchip());
+
+	/*
+	 * Create "full" VMs, as KVM_IRQFD requires an in-kernel IRQ chip. Also
+	 * create an unused vCPU as certain architectures (like arm64) need to
+	 * complete IRQ chip initialization after all possible vCPUs for a VM
+	 * have been created.
+	 */
+	vm1 = vm_create_with_one_vcpu(&unused, NULL);
+	vm2 = vm_create_with_one_vcpu(&unused, NULL);
 
 	WRITE_ONCE(__eventfd, kvm_new_eventfd());
 
diff --git a/tools/testing/selftests/kvm/lib/arm64/processor.c b/tools/testing/selftests/kvm/lib/arm64/processor.c
index 369a4c87dd8f..54f6d17c78f7 100644
--- a/tools/testing/selftests/kvm/lib/arm64/processor.c
+++ b/tools/testing/selftests/kvm/lib/arm64/processor.c
@@ -725,3 +725,8 @@ void kvm_arch_vm_release(struct kvm_vm *vm)
 	if (vm->arch.has_gic)
 		close(vm->arch.gic_fd);
 }
+
+bool kvm_arch_has_default_irqchip(void)
+{
+	return request_vgic && kvm_supports_vgic_v3();
+}
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 67f32d41a59c..40d0252f146f 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -2374,3 +2374,8 @@ bool vm_is_gpa_protected(struct kvm_vm *vm, vm_paddr_t paddr)
 	pg = paddr >> vm->page_shift;
 	return sparsebit_is_set(region->protected_phy_pages, pg);
 }
+
+__weak bool kvm_arch_has_default_irqchip(void)
+{
+	return false;
+}
diff --git a/tools/testing/selftests/kvm/lib/s390/processor.c b/tools/testing/selftests/kvm/lib/s390/processor.c
index 20cfe970e3e3..8ceeb17c819a 100644
--- a/tools/testing/selftests/kvm/lib/s390/processor.c
+++ b/tools/testing/selftests/kvm/lib/s390/processor.c
@@ -221,3 +221,8 @@ void vcpu_arch_dump(FILE *stream, struct kvm_vcpu *vcpu, uint8_t indent)
 void assert_on_unhandled_exception(struct kvm_vcpu *vcpu)
 {
 }
+
+bool kvm_arch_has_default_irqchip(void)
+{
+	return true;
+}
diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
index bff75aa341bf..0d3cfb9e9c3c 100644
--- a/tools/testing/selftests/kvm/lib/x86/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86/processor.c
@@ -1281,3 +1281,8 @@ bool sys_clocksource_is_based_on_tsc(void)
 
 	return ret;
 }
+
+bool kvm_arch_has_default_irqchip(void)
+{
+	return true;
+}

base-commit: 10fd0285305d0b48e8a3bf15d4f17fc4f3d68cb6
-- 
2.39.5

On Tue, Sep 30, 2025, Oliver Upton wrote:
> On Tue, Sep 30, 2025 at 08:14:19AM -0700, Sean Christopherson wrote:
> > > What about providing an API to do exactly that, instantiate and initialize a
> > > barebones GIC?  E.g.
> > > 
> > > 	void kvm_arch_init_barebones_irqchip(struct kvm_vm *vm)
> > > 
> > > Hmm, then we'd also need
> > > 
> > > 	void kvm_arch_vm_free(struct kvm_vm *vm)
> > > 
> > > to gracefully free the GIC, as done by dirty_log_perf_test.c.  Blech.  Though
> > > maybe we'll end up with that hook sooner or later?
> > > 
> > > All in all, I have no strong preference at this point.
> > 
> > Oliver, any thoughts?  This is causing noise in people's CIs, i.e. we should land
> > a fix sooner than later, even if it's not the "final" form. 
> 
> The lack of a default VGICv3 wound up getting in my way with some
> changes to promote selftests to run in VHE EL2, cc'ed you on that series
> since I wound up walking back my gripes here :)
> 
>   https://lore.kernel.org/kvmarm/20250917212044.294760-1-oliver.upton@linux.dev

Hah!  I saw the series but didn't read the cover letter. :-)

> That's now in Paolo's tree as of this morning. With that said, I think
> irqfd_test needs a bit more attention (below).
> 
> Thanks,
> Oliver
> 
> >From 4d0a035fb7e6cead74af4edb24fbcfdec076d321 Mon Sep 17 00:00:00 2001
> From: Oliver Upton <oliver.upton@linux.dev>
> Date: Tue, 30 Sep 2025 10:53:14 -0700
> Subject: [PATCH] KVM: selftests: Fix irqfd_test for non-x86 architectures
> 
> The KVM_IRQFD ioctl fails if no irqchip is present in-kernel, which
> isn't too surprising as there's not much KVM can do for an IRQ if it
> cannot resolve a destination.
> 
> As written the irqfd_test assumes that a 'default' VM created in
> selftests has an in-kernel irqchip created implicitly. That may be the
> case on x86 but it isn't necessarily true on other architectures.
> 
> Add an arch predicate indicating if 'default' VMs get an irqchip and
> make the irqfd_test depend on it. Work around arm64 VGIC initialization
> requirements by using vm_create_with_one_vcpu(), ignoring the created
> vCPU as it isn't used for the test.
> 
> Fixes: 7e9b231c402a ("KVM: selftests: Add a KVM_IRQFD test to verify uniqueness requirements")

Reported-by: Sebastian Ott <sebott@redhat.com>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>

> Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

Acked-by: Sean Christopherson <seanjc@google.com>