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Shutemov" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231101_153502_376792_1252FF86 X-CRM114-Status: GOOD ( 28.17 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Nov 01, 2023, Paolo Bonzini wrote: > On 11/1/23 17:36, Sean Christopherson wrote: > > > > "Allow" isn't perfect, e.g. I would much prefer a straight KVM_GUEST_MEMFD_USE_HUGEPAGES > > > > or KVM_GUEST_MEMFD_HUGEPAGES flag, but I wanted the name to convey that KVM doesn't > > > > (yet) guarantee hugepages. I.e. KVM_GUEST_MEMFD_ALLOW_HUGEPAGE is stronger than > > > > a hint, but weaker than a requirement. And if/when KVM supports a dedicated memory > > > > pool of some kind, then we can add KVM_GUEST_MEMFD_REQUIRE_HUGEPAGE. > > > I think that the current patch is fine, but I will adjust it to always > > > allow the flag, and to make the size check even if !CONFIG_TRANSPARENT_HUGEPAGE. > > > If hugepages are not guaranteed, and (theoretically) you could have no > > > hugepage at all in the result, it's okay to get this result even if THP is not > > > available in the kernel. > > Can you post a fixup patch? It's not clear to me exactly what behavior you intend > > to end up with. > > Sure, just this: > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index 7d1a33c2ad42..34fd070e03d9 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -430,10 +430,7 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > { > loff_t size = args->size; > u64 flags = args->flags; > - u64 valid_flags = 0; > - > - if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) > - valid_flags |= KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; > + u64 valid_flags = KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; > if (flags & ~valid_flags) > return -EINVAL; > @@ -441,11 +438,9 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > if (size < 0 || !PAGE_ALIGNED(size)) > return -EINVAL; > -#ifdef CONFIG_TRANSPARENT_HUGEPAGE > if ((flags & KVM_GUEST_MEMFD_ALLOW_HUGEPAGE) && > !IS_ALIGNED(size, HPAGE_PMD_SIZE)) > return -EINVAL; > -#endif That won't work, HPAGE_PMD_SIZE is valid only for CONFIG_TRANSPARENT_HUGEPAGE=y. #else /* CONFIG_TRANSPARENT_HUGEPAGE */ #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; }) #define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; }) #define HPAGE_PMD_SIZE ({ BUILD_BUG(); 0; }) ... > return __kvm_gmem_create(kvm, size, flags); > } > > Paolo > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel