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

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Message-ID: <44f17b93-cf3c-43e9-b921-5f904c13db69@intel.com>
Date: Thu, 31 Jul 2025 15:49:29 +0800
From: Xiaoyao Li <xiaoyao.li@...el.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
 Oliver Upton <oliver.upton@...ux.dev>, kvm@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
 linux-kernel@...r.kernel.org, Ira Weiny <ira.weiny@...el.com>,
 Gavin Shan <gshan@...hat.com>, Shivank Garg <shivankg@....com>,
 Vlastimil Babka <vbabka@...e.cz>, David Hildenbrand <david@...hat.com>,
 Fuad Tabba <tabba@...gle.com>, Ackerley Tng <ackerleytng@...gle.com>,
 Tao Chan <chentao@...inos.cn>, James Houghton <jthoughton@...gle.com>
Subject: Re: [PATCH v17 23/24] KVM: selftests: guest_memfd mmap() test when
 mmap is supported

On 7/30/2025 8:57 PM, Sean Christopherson wrote:
> 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);

With the above fix,

Reviewed-by: Xiaoyao Li <xiaoyao.li@...el.com>