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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, Randy Dunlap , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jason Gunthorpe , Fuad Tabba , 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 , Fuad Tabba , Xiaoyao Li X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1789084533; l=6433; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=1gG5ZbGkC7+8aa3BRkAOtEFb3BMFWAIwkdSXfAOjliA=; b=rkveUKzWAElVqvkW8O2AomhKayphQNqwoX/UCYgVOjECWqSUNWGVn0o/li/5D5EmXqxINuTkG X0Ir9UE7D7LC6JBXc0UcIqzcvZC2YVe10StOMne1c2mWpnIrfrqeFGU 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-Server: rspam08 X-Rspamd-Queue-Id: CA85518000F X-Stat-Signature: m6en4yzbfyk46khprieu6dq1c7mzfdm3 X-HE-Tag: 1789084541-104348 X-HE-Meta: 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 vA5j2eCq 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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_is_private_gfn() 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. Co-developed-by: Ackerley Tng Signed-off-by: Ackerley Tng Signed-off-by: Sean Christopherson Reviewed-by: Fuad Tabba Reviewed-by: Binbin Wu Reviewed-by: David Hildenbrand (Arm) Cc: Fuad Tabba Cc: Xiaoyao Li --- Documentation/virt/kvm/api.rst | 17 ++++++++++++----- include/linux/kvm_host.h | 6 ++++++ virt/kvm/guest_memfd.c | 26 ++++++++++++++++++++++++++ virt/kvm/kvm_main.c | 12 +++++++++++- 4 files changed, 55 insertions(+), 6 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index e0430cc750c9e..09967e0308031 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6381,11 +6381,16 @@ mapping for userspace_addr is not required to be valid/populated at the time of KVM_SET_USER_MEMORY_REGION2, e.g. shared memory can be lazily mapped/allocated on-demand. -When mapping a gfn into the guest, KVM selects shared vs. private, i.e consumes -userspace_addr vs. guest_memfd, based on the gfn's KVM_MEMORY_ATTRIBUTE_PRIVATE -state. At VM creation time, all memory is shared, i.e. the PRIVATE attribute -is '0' for all gfns. Userspace can control whether memory is shared/private by -toggling KVM_MEMORY_ATTRIBUTE_PRIVATE via KVM_SET_MEMORY_ATTRIBUTES as needed. +When mapping a gfn into the guest, KVM selects shared vs. private, i.e. consumes +userspace_addr vs. guest_memfd, based on the state in guest_memfd, which is the +sole authority on private vs. shared memory. See :ref:`KVM_CREATE_GUEST_MEMFD` +to find out more about the creation-time shared/private status. + +If in-place conversion is disabled, KVM selects shared vs. private based on the +gfn's KVM_MEMORY_ATTRIBUTE_PRIVATE state. At VM creation time, all memory is +shared, i.e. the PRIVATE attribute is '0' for all gfns. Userspace can control +whether memory is shared/private by toggling KVM_MEMORY_ATTRIBUTE_PRIVATE via +KVM_SET_MEMORY_ATTRIBUTES as needed. S390: ^^^^^ @@ -6429,6 +6434,8 @@ the state of a gfn/page as needed. The "flags" field is reserved for future extensions and must be '0'. +.. _KVM_CREATE_GUEST_MEMFD: + 4.142 KVM_CREATE_GUEST_MEMFD ---------------------------- diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 3579feb631775..b0110143d2ff8 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -2580,6 +2580,8 @@ static inline bool kvm_vm_is_private_gfn(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_is_private_gfn_t)(struct kvm *kvm, gfn_t gfn); DECLARE_STATIC_CALL(__kvm_is_private_gfn, kvm_is_private_gfn_t); @@ -2588,6 +2590,8 @@ static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn) return static_call(__kvm_is_private_gfn)(kvm, gfn); } #else +#define gmem_in_place_conversion false + static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn) { return false; @@ -2595,6 +2599,8 @@ static inline bool kvm_is_private_gfn(struct kvm *kvm, gfn_t gfn) #endif /* kvm_arch_has_private_mem */ #ifdef CONFIG_KVM_GUEST_MEMFD +bool kvm_gmem_is_private_gfn(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, int *max_order); #else diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index ce5efcacda36e..cd966eef45b69 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -478,6 +478,32 @@ static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma) return 0; } +bool kvm_gmem_is_private_gfn(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_gfn); + 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 78278730b2ae4..46d2e123448c2 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_is_private_gfn); static void kvm_init_memory_attributes(void) { + if (gmem_in_place_conversion) + static_call_update(__kvm_is_private_gfn, kvm_gmem_is_private_gfn); #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES - static_call_update(__kvm_is_private_gfn, kvm_vm_is_private_gfn); + else + static_call_update(__kvm_is_private_gfn, kvm_vm_is_private_gfn); #endif } #else -- 2.55.0.1007.g17ff1f9808-goog