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 08:09:49 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Shuah Khan <skhan@...uxfoundation.org>
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>
Subject: Re: [PATCH v13 25/35] KVM: selftests: Convert lib's mem regions to KVM_SET_USER_MEMORY_REGION2

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.

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));
--