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charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260507-gmem-inplace-conversion-v6-6-91ab5a8b19a4@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=1802; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=zSMKUjOxxa82tr34hHB/lIyi0dgSFlYMksc47el8QGc=; b=hJ896vjTW0uUAF9uO3rBIOiH5NHAk0DL09eR9y0euiFWur9ijMeWBDnfJ2NtS5VCQ0U7KoL+q r6BoruioCdBDfuBf5VaYFPrfITfiOTnp6SwjOLdc8yMs137ID9Bj4ms 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-Stat-Signature: 1cdff9ery15hwcqfzs77ma3pfe8f3c1j X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 34C9740004 X-Rspam-User: X-HE-Tag: 1778185371-718502 X-HE-Meta: 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 a+gg/Qz5 XwrDWn2G0BhTBg6q68dugTrzlp282K1r4elZc16lxRrQLOpI1yEXJQptajuEXrHhtWS6nq/lcyNelr2HFgPPnd3FF/cg8qPY9eZwP2S267fWV7sSTSSuCN5Z79Ui7PDXSOVHOfYuaXxQxqNl6eZHWdEA1xmHwfgFH1bOlSq/6Ock4PDS0HPoJOcvGF7bR5rMul0XyIoM78pDl18dgmf5OrMNpZ5iFR00O1XLHfVkfrGbPh4UrXLFbecOUHeV94XNM4KstHKAJix0HJeKsIFvKL3+95G/NQ2/aIrLQPoX4L48yuxYUKVJyd4xmTl7t4+yY1BXSpleaew5RpnTnW/fXGqAqQfgt3j9eD0juB7mBwhKpW9XI6t8EOCWK2x6fUKKSXqniCOR2uwvX51lnAd/HjOPTK8UjYdw/3oBW Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Ackerley Tng When the maximum mapping level is queried, KVM's MMU lock is held, and while the MMU lock is held, guest_memfd cannot take the filemap_invalidate_lock() to look up the current shared/private state of the gfn, for these reasons: + The MMU lock is a spinlock or rwlock and cannot be held while taking a lock that can sleep. + In guest_memfd's code paths (such as truncate), the filemap_invalidate_lock() is held while taking the MMU lock, and taking the locks in reverse order would introduce a AB-BA deadlock. Currently, the maximum mapping level is only queried from guest_memfd in the process of recovering huge pages, if dirty logging is disabled on a memslot. Dirty logging is not currently supported for guest_memfd, and guest_memfd memslots also cannot be updated. For now, bug the VM if guest_memfd needs to be queried to determine the maximum mapping level. This guard can be removed if/when support is added. Signed-off-by: Ackerley Tng --- arch/x86/kvm/mmu/mmu.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index a80a876ab4ad6..153bcc5369985 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3357,6 +3357,15 @@ int kvm_mmu_max_mapping_level(struct kvm *kvm, struct kvm_page_fault *fault, max_level = fault->max_level; is_private = fault->is_private; } else { + /* + * Memory attributes cannot be obtained from guest_memfd while + * the MMU lock is held. + */ + if (KVM_BUG_ON(static_call_query(__kvm_get_memory_attributes) == + kvm_gmem_get_memory_attributes, kvm)) { + return 0; + } + max_level = PG_LEVEL_NUM; is_private = kvm_mem_is_private(kvm, gfn); } -- 2.54.0.563.g4f69b47b94-goog