linux-kernel - Re: [PATCH v13 25/35] KVM: selftests: Convert lib's mem regions to KVM_SET_USER_MEMORY

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Date: Thu, 25 Apr 2024 10:22:11 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Dan Carpenter <dan.carpenter@...aro.org>, Shuah Khan <shuah@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
 Oliver Upton <oliver.upton@...ux.dev>, Huacai Chen <chenhuacai@...nel.org>,
 Michael Ellerman <mpe@...erman.id.au>, Anup Patel <anup@...infault.org>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Alexander Viro <viro@...iv.linux.org.uk>,
 Christian Brauner <brauner@...nel.org>,
 "Matthew Wilcox (Oracle)" <willy@...radead.org>,
 Andrew Morton <akpm@...ux-foundation.org>, kvm@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
 linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
 kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
 linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, Xiaoyao Li <xiaoyao.li@...el.com>,
 Xu Yilun <yilun.xu@...el.com>, Chao Peng <chao.p.peng@...ux.intel.com>,
 Fuad Tabba <tabba@...gle.com>, Jarkko Sakkinen <jarkko@...nel.org>,
 Anish Moorthy <amoorthy@...gle.com>, David Matlack <dmatlack@...gle.com>,
 Yu Zhang <yu.c.zhang@...ux.intel.com>,
 Isaku Yamahata <isaku.yamahata@...el.com>, Mickaël Salaün <mic@...ikod.net>, Vlastimil Babka <vbabka@...e.cz>,
 Vishal Annapurve <vannapurve@...gle.com>,
 Ackerley Tng <ackerleytng@...gle.com>,
 Maciej Szmigiero <mail@...iej.szmigiero.name>,
 David Hildenbrand <david@...hat.com>, Quentin Perret <qperret@...gle.com>,
 Michael Roth <michael.roth@....com>, Wang <wei.w.wang@...el.com>,
 Liam Merwick <liam.merwick@...cle.com>,
 Isaku Yamahata <isaku.yamahata@...il.com>,
 "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
 Naresh Kamboju <naresh.kamboju@...aro.org>,
 Anders Roxell <anders.roxell@...aro.org>,
 Benjamin Copeland <ben.copeland@...aro.org>,
 Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v13 25/35] KVM: selftests: Convert lib's mem regions to
 KVM_SET_USER_MEMORY_REGION2

On 4/25/24 09:09, Sean Christopherson wrote:
> On Thu, Apr 25, 2024, Shuah Khan wrote:
>> On 4/25/24 08:12, Dan Carpenter wrote:
>>> On Fri, Oct 27, 2023 at 11:22:07AM -0700, Sean Christopherson wrote:
>>>> Use KVM_SET_USER_MEMORY_REGION2 throughout KVM's selftests library so that
>>>> support for guest private memory can be added without needing an entirely
>>>> separate set of helpers.
>>>>
>>>> Note, this obviously makes selftests backwards-incompatible with older KVM
>>>     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>> versions from this point forward.
>>>     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>
>>> Is there a way we could disable the tests on older kernels instead of
>>> making them fail?  Check uname or something?  There is probably a
>>> standard way to do this...  It's these tests which fail.
>>
>> They shouldn't fail - the tests should be skipped on older kernels.
> 
> Ah, that makes sense.  Except for a few outliers that aren't all that interesting,
> all KVM selftests create memslots, so I'm tempted to just make it a hard requirement
> to spare us headache, e.g.
> 
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index b2262b5fad9e..4b2038b1f11f 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -2306,6 +2306,9 @@ void __attribute((constructor)) kvm_selftest_init(void)
>          /* Tell stdout not to buffer its content. */
>          setbuf(stdout, NULL);
>   
> +       __TEST_REQUIRE(kvm_has_cap(KVM_CAP_USER_MEMORY2),
> +                      "KVM selftests from v6.8+ require KVM_SET_USER_MEMORY_REGION2");
> +
>          kvm_selftest_arch_init();
>   }
> 
> --
> 
> but it's also easy enough to be more precise and skip only those that actually
> create memslots.

This is approach is what is recommended in kselfest document. Rubn as many tests
as possible and skip the ones that can't be run due to unmet dependencies.

> 
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index b2262b5fad9e..b21152adf448 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -944,6 +944,9 @@ int __vm_set_user_memory_region2(struct kvm_vm *vm, uint32_t slot, uint32_t flag
>                  .guest_memfd_offset = guest_memfd_offset,
>          };
>   
> +       __TEST_REQUIRE(kvm_has_cap(KVM_CAP_USER_MEMORY2),
> +                      "KVM selftests from v6.8+ require KVM_SET_USER_MEMORY_REGION2");
> +
>          return ioctl(vm->fd, KVM_SET_USER_MEMORY_REGION2, &region);
>   }
>   
> @@ -970,6 +973,9 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
>          size_t mem_size = npages * vm->page_size;
>          size_t alignment;
>   
> +       __TEST_REQUIRE(kvm_has_cap(KVM_CAP_USER_MEMORY2),
> +                      "KVM selftests from v6.8+ require KVM_SET_USER_MEMORY_REGION2");
> +
>          TEST_ASSERT(vm_adjust_num_guest_pages(vm->mode, npages) == npages,
>                  "Number of guest pages is not compatible with the host. "
>                  "Try npages=%d", vm_adjust_num_guest_pages(vm->mode, npages));
> --

thanks,
-- Shuah