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Sun, 5 Nov 2023 16:35:25 +0000 (UTC) Received: from avogadro.redhat.com (unknown [10.39.192.93]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3AD9D2166B26; Sun, 5 Nov 2023 16:35:18 +0000 (UTC) From: Paolo Bonzini To: Paolo Bonzini , Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Sean Christopherson , Alexander Viro , Christian Brauner , "Matthew Wilcox (Oracle)" , Andrew Morton Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Xiaoyao Li , Xu Yilun , Chao Peng , Fuad Tabba , Jarkko Sakkinen , Anish Moorthy , David Matlack , Yu Zhang , Isaku Yamahata , =?utf-8?q?Micka=C3=ABl_Sala?= =?utf-8?q?=C3=BCn?= , Vlastimil Babka , Vishal Annapurve , Ackerley Tng , Maciej Szmigiero , David Hildenbrand , Quentin Perret , Michael Roth , Wang , Liam Merwick , Isaku Yamahata , "Kirill A. Shutemov" Subject: [PATCH 36/34] KVM: Add transparent hugepage support for dedicated guest memory Date: Sun, 5 Nov 2023 17:30:39 +0100 Message-ID: <20231105163040.14904-37-pbonzini@redhat.com> In-Reply-To: <20231105163040.14904-1-pbonzini@redhat.com> References: <20231105163040.14904-1-pbonzini@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.6 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231105_163532_491368_88850760 X-CRM114-Status: GOOD ( 28.80 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org From: Sean Christopherson Extended guest_memfd to allow backing guest memory with transparent hugepages. Require userspace to opt-in via a flag even though there's no known/anticipated use case for forcing small pages as THP is optional, i.e. to avoid ending up in a situation where userspace is unaware that KVM can't provide hugepages. For simplicity, require the guest_memfd size to be a multiple of the hugepage size, e.g. so that KVM doesn't need to do bounds checking when deciding whether or not to allocate a huge folio. When reporting the max order when KVM gets a pfn from guest_memfd, force order-0 pages if the hugepage is not fully contained by the memslot binding, e.g. if userspace requested hugepages but punches a hole in the memslot bindings in order to emulate x86's VGA hole. Signed-off-by: Sean Christopherson Message-Id: <20231027182217.3615211-18-seanjc@google.com> [Allow even with CONFIG_TRANSPARENT_HUGEPAGE; dropped momentarily due to uneasiness about the API. - Paolo] Signed-off-by: Paolo Bonzini --- Documentation/virt/kvm/api.rst | 7 ++ include/uapi/linux/kvm.h | 2 + .../testing/selftests/kvm/guest_memfd_test.c | 15 ++++ tools/testing/selftests/kvm/lib/kvm_util.c | 9 +++ .../kvm/x86_64/private_mem_conversions_test.c | 7 +- virt/kvm/guest_memfd.c | 70 ++++++++++++++++--- 6 files changed, 101 insertions(+), 9 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 38882263278d..c13ede498369 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6318,6 +6318,8 @@ and cannot be resized (guest_memfd files do however support PUNCH_HOLE). __u64 reserved[6]; }; + #define KVM_GUEST_MEMFD_ALLOW_HUGEPAGE (1ULL << 0) + Conceptually, the inode backing a guest_memfd file represents physical memory, i.e. is coupled to the virtual machine as a thing, not to a "struct kvm". The file itself, which is bound to a "struct kvm", is that instance's view of the @@ -6334,6 +6336,11 @@ most one mapping per page, i.e. binding multiple memory regions to a single guest_memfd range is not allowed (any number of memory regions can be bound to a single guest_memfd file, but the bound ranges must not overlap). +If KVM_GUEST_MEMFD_ALLOW_HUGEPAGE is set in flags, KVM will attempt to allocate +and map hugepages for the guest_memfd file. This is currently best effort. If +KVM_GUEST_MEMFD_ALLOW_HUGEPAGE is set, the size must be aligned to the maximum +transparent hugepage size supported by the kernel + See KVM_SET_USER_MEMORY_REGION2 for additional details. 5. The kvm_run structure diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index e9cb2df67a1d..b4ba4b53b834 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -2316,4 +2316,6 @@ struct kvm_create_guest_memfd { __u64 reserved[6]; }; +#define KVM_GUEST_MEMFD_ALLOW_HUGEPAGE (1ULL << 0) + #endif /* __LINUX_KVM_H */ diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c index ea0ae7e25330..c15de9852316 100644 --- a/tools/testing/selftests/kvm/guest_memfd_test.c +++ b/tools/testing/selftests/kvm/guest_memfd_test.c @@ -123,6 +123,7 @@ static void test_invalid_punch_hole(int fd, size_t page_size, size_t total_size) static void test_create_guest_memfd_invalid(struct kvm_vm *vm) { + uint64_t valid_flags = 0; size_t page_size = getpagesize(); uint64_t flag; size_t size; @@ -135,9 +136,23 @@ static void test_create_guest_memfd_invalid(struct kvm_vm *vm) size); } + if (thp_configured()) { + for (size = page_size * 2; size < get_trans_hugepagesz(); size += page_size) { + fd = __vm_create_guest_memfd(vm, size, KVM_GUEST_MEMFD_ALLOW_HUGEPAGE); + TEST_ASSERT(fd == -1 && errno == EINVAL, + "guest_memfd() with non-hugepage-aligned page size '0x%lx' should fail with EINVAL", + size); + } + + valid_flags = KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; + } + for (flag = 1; flag; flag <<= 1) { uint64_t bit; + if (flag & valid_flags) + continue; + fd = __vm_create_guest_memfd(vm, page_size, flag); TEST_ASSERT(fd == -1 && errno == EINVAL, "guest_memfd() with flag '0x%lx' should fail with EINVAL", diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c index d05d95cc3693..ed81a00e5df1 100644 --- a/tools/testing/selftests/kvm/lib/kvm_util.c +++ b/tools/testing/selftests/kvm/lib/kvm_util.c @@ -1022,6 +1022,15 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type, if (flags & KVM_MEM_GUEST_MEMFD) { if (guest_memfd < 0) { uint32_t guest_memfd_flags = 0; + + /* + * Allow hugepages for the guest memfd backing if the + * "normal" backing is allowed/required to be huge. + */ + if (src_type != VM_MEM_SRC_ANONYMOUS && + src_type != VM_MEM_SRC_SHMEM) + guest_memfd_flags |= KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; + TEST_ASSERT(!guest_memfd_offset, "Offset must be zero when creating new guest_memfd"); guest_memfd = vm_create_guest_memfd(vm, mem_size, guest_memfd_flags); diff --git a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c index 4d6a37a5d896..f707fd401a4f 100644 --- a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c +++ b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c @@ -380,6 +380,7 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, uint32_t const size_t slot_size = memfd_size / nr_memslots; struct kvm_vcpu *vcpus[KVM_MAX_VCPUS]; pthread_t threads[KVM_MAX_VCPUS]; + uint64_t memfd_flags; struct kvm_vm *vm; int memfd, i, r; @@ -395,7 +396,11 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, uint32_t vm_enable_cap(vm, KVM_CAP_EXIT_HYPERCALL, (1 << KVM_HC_MAP_GPA_RANGE)); - memfd = vm_create_guest_memfd(vm, memfd_size, 0); + if (backing_src_can_be_huge(src_type)) + memfd_flags = KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; + else + memfd_flags = 0; + memfd = vm_create_guest_memfd(vm, memfd_size, memfd_flags); for (i = 0; i < nr_memslots; i++) vm_mem_add(vm, src_type, BASE_DATA_GPA + slot_size * i, diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index e65f4170425c..3e48e8997626 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -13,14 +13,44 @@ struct kvm_gmem { struct list_head entry; }; +static struct folio *kvm_gmem_get_huge_folio(struct inode *inode, pgoff_t index, unsigned order) +{ + pgoff_t npages = 1UL << order; + pgoff_t huge_index = round_down(index, npages); + unsigned long flags = (unsigned long)inode->i_private; + struct address_space *mapping = inode->i_mapping; + gfp_t gfp = mapping_gfp_mask(mapping); + struct folio *folio; + + if (!(flags & KVM_GUEST_MEMFD_ALLOW_HUGEPAGE)) + return NULL; + + if (filemap_range_has_page(mapping, (loff_t)huge_index << PAGE_SHIFT, + (loff_t)(huge_index + npages - 1) << PAGE_SHIFT)) + return NULL; + + folio = filemap_alloc_folio(gfp, order); + if (!folio) + return NULL; + + if (filemap_add_folio(mapping, folio, huge_index, gfp)) { + folio_put(folio); + return NULL; + } + + return folio; +} + static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index) { struct folio *folio; - /* TODO: Support huge pages. */ - folio = filemap_grab_folio(inode->i_mapping, index); - if (IS_ERR_OR_NULL(folio)) - return NULL; + folio = kvm_gmem_get_huge_folio(inode, index, PMD_ORDER); + if (!folio) { + folio = filemap_grab_folio(inode->i_mapping, index); + if (IS_ERR_OR_NULL(folio)) + return NULL; + } /* * Use the up-to-date flag to track whether or not the memory has been @@ -366,6 +396,7 @@ static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags) inode->i_mode |= S_IFREG; inode->i_size = size; mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); + mapping_set_large_folios(inode->i_mapping); mapping_set_unmovable(inode->i_mapping); /* Unmovable mappings are supposed to be marked unevictable as well. */ WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping)); @@ -389,7 +420,7 @@ 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; + u64 valid_flags = KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; if (flags & ~valid_flags) return -EINVAL; @@ -397,6 +428,13 @@ 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 + BUILD_BUG_ON(PMD_SIZE != HPAGE_PMD_SIZE); +#endif + if ((flags & KVM_GUEST_MEMFD_ALLOW_HUGEPAGE) && + !IS_ALIGNED(size, PMD_SIZE)) + return -EINVAL; + return __kvm_gmem_create(kvm, size, flags); } @@ -491,7 +529,7 @@ void kvm_gmem_unbind(struct kvm_memory_slot *slot) int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, kvm_pfn_t *pfn, int *max_order) { - pgoff_t index = gfn - slot->base_gfn + slot->gmem.pgoff; + pgoff_t index, huge_index; struct kvm_gmem *gmem; struct folio *folio; struct page *page; @@ -504,6 +542,7 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gmem = file->private_data; + index = gfn - slot->base_gfn + slot->gmem.pgoff; if (WARN_ON_ONCE(xa_load(&gmem->bindings, index) != slot)) { r = -EIO; goto out_fput; @@ -523,9 +562,24 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, page = folio_file_page(folio, index); *pfn = page_to_pfn(page); - if (max_order) - *max_order = 0; + if (!max_order) + goto success; + *max_order = compound_order(compound_head(page)); + if (!*max_order) + goto success; + + /* + * The folio can be mapped with a hugepage if and only if the folio is + * fully contained by the range the memslot is bound to. Note, the + * caller is responsible for handling gfn alignment, this only deals + * with the file binding. + */ + huge_index = ALIGN(index, 1ull << *max_order); + if (huge_index < ALIGN(slot->gmem.pgoff, 1ull << *max_order) || + huge_index + (1ull << *max_order) > slot->gmem.pgoff + slot->npages) + *max_order = 0; +success: r = 0; out_unlock: