Subject: Re: [PATCH v17 23/24] KVM: selftests: guest_memfd mmap() test when mmap is supported

From: Sean Christopherson <[email-masked]>
Date: Wed, 30 Jul 2025 05:57:06 -0700

On Wed, Jul 30, 2025, Xiaoyao Li wrote:
> On 7/30/2025 6:54 AM, Sean Christopherson wrote:
> 
> ...
> 
> > +int main(int argc, char *argv[])
> > +{
> > +	unsigned long vm_types, vm_type;
> > +
> > +	TEST_REQUIRE(kvm_has_cap(KVM_CAP_GUEST_MEMFD));
> > +
> > +	/*
> > +	 * Not all architectures support KVM_CAP_VM_TYPES. However, those that
> > +	 * support guest_memfd have that support for the default VM type.
> > +	 */
> > +	vm_types = kvm_check_cap(KVM_CAP_VM_TYPES);
> > +	if (!vm_types)
> > +		vm_types = VM_TYPE_DEFAULT;
> > +
> > +	for_each_set_bit(vm_type, &vm_types, BITS_PER_TYPE(vm_types))
> > +		test_guest_memfd(vm_type);
> 
> For ARCHes that don't support KVM_CAP_VM_TYPES, e.g., ARM, vm_types is 0
> (VM_TYPE_DEFAULT). the for_each_set_bit() loop will not execute any
> iteration at all.

Doh, indeed.

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index b86bf89a71e0..b3ca6737f304 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -372,7 +372,7 @@ int main(int argc, char *argv[])
         */
        vm_types = kvm_check_cap(KVM_CAP_VM_TYPES);
        if (!vm_types)
-               vm_types = VM_TYPE_DEFAULT;
+               vm_types = BIT(VM_TYPE_DEFAULT);
 
        for_each_set_bit(vm_type, &vm_types, BITS_PER_TYPE(vm_types))
                test_guest_memfd(vm_type);