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charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260428-gmem-inplace-conversion-v5-6-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=1802; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=mE1k3tJABrFyLvPsAUThPSR13SSUuI4MykLoB5ZQsPI=; b=CMxTYYNPO2Cg0DwwVYx4rM0CeYzUOqMMYtEiADkSrj386FCCj4wMlpDsBDm5m+GMCeMOCbzOi lMB9ng0Vh81CYdMxjc8AIWrpzjoE01tqhLnJELjyZNXaKHIOyygmT3c 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: tx5kbjxqk6gwuuaumb7raqm3z6t6jpkb X-Rspamd-Queue-Id: 7537440012 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1777418721-98309 X-HE-Meta: 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 hcL90Qv3 nEAa9QEtDJfUEdFJMOBqdpvLnGkQqquG/CdnbjzDfN692E5/ofPXQPGVE4lz6oOXKRzAUF9CVjv3+KAxQYF5wsZ5TZHXlbuKhbnWEtaFfEosm/Z4xQunnIl0iaKnfO68wOl9JFBc4fFvjtMleLqhsqhh3h9rklM/W62ZwIwdjBCnxRr/ytXMXqazVvJWQHEglPM0UQ0fJTlvQgCuQ8IWY5CYZR7E+3SQGu4caUFXui9Icesmm+jyeI8J4uceGSQF0eNtN0U+CIOnkNHuT0O5ELVK1jQxsw8TtPpcDz0XqEGAkopUG4A0P0w28Y3bSXCGpnIPMgzuooNAUU8mx5sDCFs+05mRr4zyT2a7VpPJI5YN02HnER57K7nkNtcna5/cYmMFDa7XAdVX4VqgeOnZxKRPMJUt4HLAFFXBe 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 8276d7ca02036..2cc848bddf190 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3364,6 +3364,15 @@ 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); } -- 2.54.0.545.g6539524ca2-goog