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charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260428-gmem-inplace-conversion-v5-5-d8608ccfca22@google.com> References: <20260428-gmem-inplace-conversion-v5-0-d8608ccfca22@google.com> In-Reply-To: <20260428-gmem-inplace-conversion-v5-0-d8608ccfca22@google.com> To: aik@amd.com, andrew.jones@linux.dev, binbin.wu@linux.intel.com, brauner@kernel.org, chao.p.peng@linux.intel.com, david@kernel.org, ira.weiny@intel.com, jmattson@google.com, jthoughton@google.com, michael.roth@amd.com, oupton@kernel.org, pankaj.gupta@amd.com, qperret@google.com, rick.p.edgecombe@intel.com, rientjes@google.com, shivankg@amd.com, steven.price@arm.com, tabba@google.com, willy@infradead.org, wyihan@google.com, yan.y.zhao@intel.com, forkloop@google.com, pratyush@kernel.org, suzuki.poulose@arm.com, aneesh.kumar@kernel.org, Paolo Bonzini , Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Shuah Khan , Shuah Khan , Vishal Annapurve , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Youngjun Park , Qi Zheng , Shakeel Butt , Kiryl Shutsemau , Jason Gunthorpe , Vlastimil Babka Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev, Ackerley Tng X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1777418714; l=3888; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=EYm5H+HZKG4huNzVvIwI6VbVarVyCkhtRQI1zH0BvXc=; b=l8oQnEGJFxSn4EiTXE9P6FteSO5rSVnbUWVF00usM5p6WOsYdDAKlFUyKJoLPK+1ALTEHeZey 13tyngurIdlAeB99TrW25+XBk4+2F65hxFbWt3QsxqTVrvWAtbflm0S X-Developer-Key: i=ackerleytng@google.com; a=ed25519; pk=sAZDYXdm6Iz8FHitpHeFlCMXwabodTm7p8/3/8xUxuU= X-Endpoint-Received: by B4 Relay for ackerleytng@google.com/20260225 with auth_id=649 X-Original-From: Ackerley Tng Reply-To: ackerleytng@google.com X-Rspam-User: X-Rspamd-Queue-Id: 7399E100014 X-Rspamd-Server: rspam06 X-Stat-Signature: ydsgun57a6stft3rd5ghqrq8nwoebzox X-HE-Tag: 1777418721-738747 X-HE-Meta: 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 I6AbTrlR 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Sean Christopherson Implement kvm_gmem_get_memory_attributes() for guest_memfd to allow the KVM core and architecture code to query per-GFN memory attributes. kvm_gmem_get_memory_attributes() finds the memory slot for a given GFN and queries the guest_memfd file's to determine if the page is marked as private. If vm_memory_attributes is not enabled, there is no shared/private tracking at the VM level. Install the guest_memfd implementation as long as guest_memfd is enabled to give guest_memfd a chance to respond on attributes. guest_memfd should look up attributes regardless of whether this memslot is gmem-only since attributes are now tracked by gmem regardless of whether mmap() is enabled. Signed-off-by: Sean Christopherson Co-developed-by: Ackerley Tng Signed-off-by: Ackerley Tng --- include/linux/kvm_host.h | 2 ++ virt/kvm/guest_memfd.c | 37 +++++++++++++++++++++++++++++++++++++ virt/kvm/kvm_main.c | 3 +++ 3 files changed, 42 insertions(+) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index c5ba2cb34e45c..28a54298d27db 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -2557,6 +2557,8 @@ bool kvm_arch_post_set_memory_attributes(struct kvm *kvm, struct kvm_gfn_range *range); #endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */ +unsigned long kvm_gmem_get_memory_attributes(struct kvm *kvm, gfn_t gfn); + #ifdef CONFIG_KVM_GUEST_MEMFD int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, kvm_pfn_t *pfn, struct page **page, diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 17e5a23fec0a1..e56f89640d050 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -515,6 +515,43 @@ static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma) return 0; } +unsigned long kvm_gmem_get_memory_attributes(struct kvm *kvm, gfn_t gfn) +{ + struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn); + struct inode *inode; + unsigned long attrs; + + /* + * If this gfn has no associated memslot, there's no chance of the gfn + * being backed by private memory, since guest_memfd must be used for + * private memory, and guest_memfd must be associated with some memslot. + */ + if (!slot) + return 0; + + CLASS(gmem_get_file, file)(slot); + if (!file) + return 0; + + inode = file_inode(file); + + /* + * Acquire the filemap lock to ensure the mtree lookup gets a + * stable result. The caller _must_ still protect consumption + * of private vs. shared by checking + * mmu_invalidate_retry_gfn() under mmu_lock to serialize + * against ongoing attribute updates. Acquiring the filemap + * lock only ensures a stable _lookup_, the result can become + * stale as soon as the lock is dropped. + */ + filemap_invalidate_lock_shared(inode->i_mapping); + attrs = kvm_gmem_get_attributes(inode, kvm_gmem_get_index(slot, gfn)); + filemap_invalidate_unlock_shared(inode->i_mapping); + + return attrs; +} +EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_memory_attributes); + static struct file_operations kvm_gmem_fops = { .mmap = kvm_gmem_mmap, .open = generic_file_open, diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index ee26f1d9b5fda..4139e903f756a 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2653,6 +2653,9 @@ static void kvm_init_memory_attributes(void) if (vm_memory_attributes) static_call_update(__kvm_get_memory_attributes, kvm_get_vm_memory_attributes); + else if (IS_ENABLED(CONFIG_KVM_GUEST_MEMFD)) + static_call_update(__kvm_get_memory_attributes, + kvm_gmem_get_memory_attributes); else static_call_update(__kvm_get_memory_attributes, (void *)__static_call_return0); -- 2.54.0.545.g6539524ca2-goog