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charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260507-gmem-inplace-conversion-v6-5-91ab5a8b19a4@google.com> References: <20260507-gmem-inplace-conversion-v6-0-91ab5a8b19a4@google.com> In-Reply-To: <20260507-gmem-inplace-conversion-v6-0-91ab5a8b19a4@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, liam@infradead.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=1778185365; l=3662; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=RaMQqb1Z3D/y4hZGPqiuTqpIzc23thZTbu/49XtlXbw=; b=1zykl/Xo6MJwvW7UdzwGuXat4SRBXAcuvjLNENFmIVlxHo6bIlePihDwmkqGB8eeWuaq+1N86 yxx0tAIpyWvA3KJHxf0UsKu9BcawQ4ofUU0sJNyjb8XLcAhExPvxCVW 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: B4D991C000B X-Rspamd-Server: rspam04 X-Stat-Signature: te9z6xg687wmbg51dyfpfu9js3n9fy4i X-HE-Tag: 1778185371-852472 X-HE-Meta: U2FsdGVkX18rQ5RvqEGRdMcylm7g53pnGQCCHtx7mpfeALAnOTt7b5GwH3exDAiLBhMeHVvIjoeQq5OBN7SLTaYTh/ahGPIcBq/fD30hGCpfCo+VrLtgV7erxPGByzKh7dHA6P2SXR9SOH4ypUw4Go5bs7bGx096mLdFdWYsB9M26Pore56e7S8tQI28cNQkDP/hctmByEfvNfzI4QzHrWzCLfT6uIfAzm5dgH5M1iJqjyj5CwMx9+9Kl6EmouF/0y5hNTNPYy+nrGhlKmEcSF1E363GbfaEQO+Jox7+CR6MU7hOABVjMi1A/a8PkbGSZr++bBMGE33ZZoSqCUMWw42ey0wb2eLh82tyjLVdB0CoP1cGgwulVK3hx1lndwIICl6HlBTyKIZL5Vucm7ygRb7JQzoru9OmxBAuR4eMnNZNEtnOGiW4VfpbqBg4FBQE0NLHaoac8wAHYxAhqLRV0zB9fu89/oLSUQ6QrSJekCHzOQ6NQcRaV3K+ZD7wMToXtJRdAUFvbE/SmOtkxL2IRqo1KiVdAvPwRiiojfVOrsi3wHpRMNesoKbhTnRcPfkpnM6/hrjU2+fZDuwzWNBYWhSJKuv9Kn+dLvWQRfQVnKBiY2HuxFvwHm+3KntvcSDtREHowX56l+o5FL/tKRNZqxUat3bYA1ldz8dtAlrjdIa1gje/K7G9cJFShMMEyqJ2Ie0eN8lcGV9WOLvjYmfZbuYePcJYa6z7DdyWK6MaS+fPLugQmnROQwqVcfbk06xwQFfVyBcLWwuHdw7Lbi7hWvFFzBX1sx6VmsQTBMEgzrj6I5y7DFJvts9jjCFdQjOpC7o4Fz8d+9OsegnF8a38wN/G2Oi16vFon1Z7AcxDWaqNpMgW6f654OTJJuCpx05U/wIi13NpxbYXGvbcLJCUdJcZe7bexmTGqmpaatLrOuYuzcMyK5RN0hZO/7GqPe2Xw0wGP50NOypcepdXnkY jlosh6GI 0DFBjz/F4/Uf08GZf0vj8wdrVl1Lsx0AjCirT9T5B9iaryzSajER6MG35a0LlGjZYPdGaksWRb8ovb3nInuyGwJQDOYTfHZ6i2/+VqzWPRzkOOqUenRS1p+sZKoNOL2lKwzpr5kW4kx//cCcc4XJ2UOKwWp1ZNl2Xtd9fDHr4krktafuNsDRo3SJRL4WnN1Wzi7BmBz44gwLAVDnjDwrNtxotO13fHCRSUVG+4/15bmFejhmbHGjdQgpJ9gE9xWbR7pAxRQLGvZVBv/+PrqE++EqsLb9XHI7H8C+t1H5/cjuvaQS7tXDiJ33PoedWqozTVFfoEWtJDI0J5HFvvIwF5iNJsbeIt8TeUzTpZNzCcPti3ukRZgAYuBu1d5F+/xsll+dzS/LaiZ8cqXaINlRDJfKHqdNqsaqlLjXgO4dNnq0Mdd4/v+0ywSPEeQmQ78uN3PhFLjpaoEgfvBjGPXpNwSwnKnXa7lSrUyI/S7k41aLE1CC7NsdUIKJczQ== 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 | 31 +++++++++++++++++++++++++++++++ virt/kvm/kvm_main.c | 3 +++ 3 files changed, 36 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 5011d38820d0d..f055e058a3f28 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -509,6 +509,37 @@ 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; + + /* + * 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); + + /* + * Rely on the maple tree's internal RCU lock to ensure a + * stable result. This result can become stale as soon as the + * lock is dropped, so 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. + */ + return kvm_gmem_get_attributes(inode, kvm_gmem_get_index(slot, gfn)); +} +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); -- 2.54.0.563.g4f69b47b94-goog