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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 , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Youngjun Park , Qi Zheng , Shakeel Butt , Kiryl Shutsemau , Baoquan He , Jason Gunthorpe , John Hubbard , Peter Xu , tarunsahu@google.com, Jason Gunthorpe , Vlastimil Babka , Baoquan He 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 , Xiaoyao Li X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1786139565; l=4469; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=WLHFPoezUAm21n5cIFWjuAvOHkt2CQoZ0rZKzRZuazc=; b=ZDOH0/Oj5SJ3cr7plA8V5KsJ2F57SIEEItjUXWHMqaX8nEorDWE/Syxgz2w0EEtbnfoa9n15i Z4Jw6LnCohfCvMN0mc4oVdHsVk2dT8aCyEXPTbtZygtHYC2VjIp2QOD 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-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 317014000B X-Stat-Signature: py8b868g8cehihzd7xeq1qzg93y8h4ng X-Rspam-User: X-HE-Tag: 1786139572-139706 X-HE-Meta: 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 kpPhjD1u 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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 Stub in global variable to enable in-place guest_memfd private<=>shared memory conversion, which will eventually be exposed to userspace via a module param, and wire up the __kvm_mem_is_private() static call to the guest_memfd version when in-place conversion is enabled, i.e. when gmem is the sole authority on private vs. shared memory. Cc: Fuad Tabba Cc: Xiaoyao Li Signed-off-by: Sean Christopherson Co-developed-by: Ackerley Tng Signed-off-by: Ackerley Tng --- include/linux/kvm_host.h | 6 ++++++ virt/kvm/guest_memfd.c | 26 ++++++++++++++++++++++++++ virt/kvm/kvm_main.c | 12 +++++++++++- 3 files changed, 43 insertions(+), 1 deletion(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 65fbce46b63f4..9477ecebbbced 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -2580,6 +2580,8 @@ static inline bool kvm_vm_mem_is_private(struct kvm *kvm, gfn_t gfn) #endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */ #ifdef kvm_arch_has_private_mem +extern bool gmem_in_place_conversion; + typedef bool (kvm_mem_is_private_t)(struct kvm *kvm, gfn_t gfn); DECLARE_STATIC_CALL(__kvm_mem_is_private, kvm_mem_is_private_t); @@ -2588,6 +2590,8 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) return static_call(__kvm_mem_is_private)(kvm, gfn); } #else +#define gmem_in_place_conversion false + static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) { return false; @@ -2595,6 +2599,8 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) #endif /* kvm_arch_has_private_mem */ #ifdef CONFIG_KVM_GUEST_MEMFD +bool kvm_gmem_is_private(struct kvm *kvm, gfn_t gfn); + int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, kvm_pfn_t *pfn, struct page **page, int *max_order); diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 1f1ae61b4878b..75979c885e030 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -475,6 +475,32 @@ static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma) return 0; } +bool kvm_gmem_is_private(struct kvm *kvm, gfn_t gfn) +{ + struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn); + struct inode *inode; + + 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_ protect consumption of private vs. shared either by + * holding guest_memfd's invalidate lock for the entire duration, or by + * checking mmu_invalidate_retry_gfn() under mmu_lock to serialize + * against concurrent attribute updates. + */ + return kvm_gmem_is_private_mem(inode, kvm_gmem_get_index(slot, gfn)); +} +EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_is_private); + 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 a01d336eab18b..0a5a1bee8de0f 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -102,6 +102,10 @@ EXPORT_SYMBOL_FOR_KVM_INTERNAL(halt_poll_ns_shrink); static bool __ro_after_init allow_unsafe_mappings; module_param(allow_unsafe_mappings, bool, 0444); +#ifdef kvm_arch_has_private_mem +bool __ro_after_init gmem_in_place_conversion = false; +#endif + /* * Ordering of locks: * @@ -2423,6 +2427,9 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm, static u64 kvm_supported_vm_mem_attributes(struct kvm *kvm) { #ifdef kvm_arch_has_private_mem + if (gmem_in_place_conversion) + return 0; + if (!kvm || kvm_arch_has_private_mem(kvm)) return KVM_MEMORY_ATTRIBUTE_PRIVATE; #endif @@ -2634,8 +2641,11 @@ EXPORT_STATIC_CALL_GPL(__kvm_mem_is_private); static void kvm_init_memory_attributes(void) { + if (gmem_in_place_conversion) + static_call_update(__kvm_mem_is_private, kvm_gmem_is_private); #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES - static_call_update(__kvm_mem_is_private, kvm_vm_mem_is_private); + else + static_call_update(__kvm_mem_is_private, kvm_vm_mem_is_private); #endif } #else -- 2.55.0.654.g21b8a5bc05-goog