From: "Mike Rapoport (Microsoft)" <[email protected]> * Export handle_userfault() for KVM module so that fault() handler in guest_memfd would be able to notify userspace about page faults in its address space. * Implement get_pagecache_folio() for guest_memfd. * And finally, introduce UFFD_FEATURE_MINOR_GENERIC that will allow using userfaultfd minor mode with memory types other than shmem and hugetlb provided they are allowed to call handle_userfault() and implement get_pagecache_folio().
Signed-off-by: Mike Rapoport (Microsoft) <[email protected]> --- fs/userfaultfd.c | 4 +++- include/uapi/linux/userfaultfd.h | 8 +++++++- virt/kvm/guest_memfd.c | 30 ++++++++++++++++++++++++++++++ 3 files changed, 40 insertions(+), 2 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 54c6cc7fe9c6..964fa2662d5c 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -537,6 +537,7 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason) out: return ret; } +EXPORT_SYMBOL_FOR_MODULES(handle_userfault, "kvm"); static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, struct userfaultfd_wait_queue *ewq) @@ -1978,7 +1979,8 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx, uffdio_api.features = UFFD_API_FEATURES; #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR uffdio_api.features &= - ~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM); + ~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM | + UFFD_FEATURE_MINOR_GENERIC); #endif #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP; diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h index 2841e4ea8f2c..c5cbd4a5a26e 100644 --- a/include/uapi/linux/userfaultfd.h +++ b/include/uapi/linux/userfaultfd.h @@ -42,7 +42,8 @@ UFFD_FEATURE_WP_UNPOPULATED | \ UFFD_FEATURE_POISON | \ UFFD_FEATURE_WP_ASYNC | \ - UFFD_FEATURE_MOVE) + UFFD_FEATURE_MOVE | \ + UFFD_FEATURE_MINOR_GENERIC) #define UFFD_API_IOCTLS \ ((__u64)1 << _UFFDIO_REGISTER | \ (__u64)1 << _UFFDIO_UNREGISTER | \ @@ -210,6 +211,10 @@ struct uffdio_api { * UFFD_FEATURE_MINOR_SHMEM indicates the same support as * UFFD_FEATURE_MINOR_HUGETLBFS, but for shmem-backed pages instead. * + * UFFD_FEATURE_MINOR_GENERIC indicates that minor faults can be + * intercepted for file-backed memory in case subsystem backing this + * memory supports it. + * * UFFD_FEATURE_EXACT_ADDRESS indicates that the exact address of page * faults would be provided and the offset within the page would not be * masked. @@ -248,6 +253,7 @@ struct uffdio_api { #define UFFD_FEATURE_POISON (1<<14) #define UFFD_FEATURE_WP_ASYNC (1<<15) #define UFFD_FEATURE_MOVE (1<<16) +#define UFFD_FEATURE_MINOR_GENERIC (1<<17) __u64 features; __u64 ioctls; diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index fbca8c0972da..5e3c63307fdf 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -4,6 +4,7 @@ #include <linux/kvm_host.h> #include <linux/pagemap.h> #include <linux/anon_inodes.h> +#include <linux/userfaultfd_k.h> #include "kvm_mm.h" @@ -369,6 +370,12 @@ static vm_fault_t kvm_gmem_fault_user_mapping(struct vm_fault *vmf) return vmf_error(err); } + if (userfaultfd_minor(vmf->vma)) { + folio_unlock(folio); + folio_put(folio); + return handle_userfault(vmf, VM_UFFD_MINOR); + } + if (WARN_ON_ONCE(folio_test_large(folio))) { ret = VM_FAULT_SIGBUS; goto out_folio; @@ -390,8 +397,31 @@ static vm_fault_t kvm_gmem_fault_user_mapping(struct vm_fault *vmf) return ret; } +#ifdef CONFIG_USERFAULTFD +static struct folio *kvm_gmem_get_pagecache_folio(struct vm_area_struct *vma, + pgoff_t pgoff) +{ + struct inode *inode = file_inode(vma->vm_file); + struct folio *folio; + + folio = kvm_gmem_get_folio(inode, pgoff); + if (IS_ERR_OR_NULL(folio)) + return folio; + + if (!folio_test_uptodate(folio)) { + clear_highpage(folio_page(folio, 0)); + kvm_gmem_mark_prepared(folio); + } + + return folio; +} +#endif + static const struct vm_operations_struct kvm_gmem_vm_ops = { .fault = kvm_gmem_fault_user_mapping, +#ifdef CONFIG_USERFAULTFD + .get_pagecache_folio = kvm_gmem_get_pagecache_folio, +#endif }; static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma) -- 2.50.1
