From: Ackerley Tng <[email protected]> Introduce a function for KVM to check the private/shared status of guest memory at a given GFN.
This will be used in a later patch. Co-developed-by: Sean Christopherson <[email protected]> Signed-off-by: Sean Christopherson <[email protected]> Reviewed-by: Xiaoyao Li <[email protected]> Reviewed-by: Fuad Tabba <[email protected]> Tested-by: Shivank Garg <[email protected]> Signed-off-by: Ackerley Tng <[email protected]> --- include/linux/kvm_host.h | 2 ++ virt/kvm/guest_memfd.c | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 34 insertions(+) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 438567e3fa6a1..73f564b87a324 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -2594,6 +2594,8 @@ 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 8c7709a352cc7..33c9830190e2e 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -474,6 +474,38 @@ 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; + + /* + * guest_memfd is the only provider of private memory and + * guest_memfd must be used with a memslot, hence if there's + * no associated memslot, there's no chance of this gfn being + * private. + */ + 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_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, -- 2.55.0.508.g3f0d502094-goog
