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Fri, 27 Oct 2023 11:22:59 -0700 (PDT) Date: Fri, 27 Oct 2023 11:21:59 -0700 In-Reply-To: <20231027182217.3615211-1-seanjc@google.com> Mime-Version: 1.0 References: <20231027182217.3615211-1-seanjc@google.com> X-Mailer: git-send-email 2.42.0.820.g83a721a137-goog Message-ID: <20231027182217.3615211-18-seanjc@google.com> Subject: [PATCH v13 17/35] KVM: Add transparent hugepage support for dedicated guest memory From: Sean Christopherson 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 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Sean Christopherson Cc: kvm@vger.kernel.org, David Hildenbrand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Chao Peng , linux-riscv@lists.infradead.org, Isaku Yamahata , Xiaoyao Li , Wang , Fuad Tabba , linux-arm-kernel@lists.infradead.org, Maciej Szmigiero , Michael Roth , Ackerley Tng , David Matlack , Vlastimil Babka , =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= , Isaku Yamahata , Quentin Perret , kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, Jarkko Sakkinen , Yu Zhang , "Kirill A . Shutemov" , kvm-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, Liam Merwick , Vishal Annapurve , linuxppc-dev@lists.ozlabs.org, Xu Yilun , Anish Moorthy Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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 Signed-off-by: Sean Christopherson --- Documentation/virt/kvm/api.rst | 7 ++++ include/uapi/linux/kvm.h | 2 + virt/kvm/guest_memfd.c | 73 ++++++++++++++++++++++++++++++---- 3 files changed, 75 insertions(+), 7 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index e82c69d5e755..7f00c310c24a 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6176,6 +6176,8 @@ 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 @@ -6192,6 +6194,11 @@ 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 25caee8d1a80..33d542de0a61 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -2303,4 +2303,6 @@ struct kvm_create_guest_memfd { __u64 reserved[6]; }; +#define KVM_GUEST_MEMFD_ALLOW_HUGEPAGE (1ULL << 0) + #endif /* __LINUX_KVM_H */ diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 98a12da80214..94bc478c26f3 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -13,14 +13,47 @@ struct kvm_gmem { struct list_head entry; }; +static struct folio *kvm_gmem_get_huge_folio(struct inode *inode, pgoff_t index) +{ +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + unsigned long huge_index = round_down(index, HPAGE_PMD_NR); + 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, huge_index << PAGE_SHIFT, + (huge_index + HPAGE_PMD_NR - 1) << PAGE_SHIFT)) + return NULL; + + folio = filemap_alloc_folio(gfp, HPAGE_PMD_ORDER); + if (!folio) + return NULL; + + if (filemap_add_folio(mapping, folio, huge_index, gfp)) { + folio_put(folio); + return NULL; + } + + return folio; +#else + return NULL; +#endif +} + 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); + 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 @@ -373,6 +406,7 @@ 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)); @@ -398,12 +432,21 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) u64 flags = args->flags; u64 valid_flags = 0; + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) + valid_flags |= KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; + if (flags & ~valid_flags) return -EINVAL; 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 + return __kvm_gmem_create(kvm, size, flags); } @@ -501,7 +544,7 @@ 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; @@ -514,6 +557,7 @@ 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; @@ -533,9 +577,24 @@ 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) + 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: