diff options
| -rw-r--r-- | virt/kvm/guest_memfd.c | 110 |
1 files changed, 66 insertions, 44 deletions
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 9271aba9b7b3..5af278c7adba 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -25,7 +25,7 @@ static inline kvm_pfn_t folio_file_pfn(struct folio *folio, pgoff_t index) return folio_pfn(folio) + (index & (folio_nr_pages(folio) - 1)); } -static int kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct folio *folio) +static int __kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct folio *folio) { #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_PREPARE struct list_head *gmem_list = &inode->i_mapping->i_private_list; @@ -59,49 +59,63 @@ static int kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct fol return 0; } -/* Returns a locked folio on success. */ -static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index, bool prepare) +/* + * Process @folio, which contains @gfn, so that the guest can use it. + * The folio must be locked and the gfn must be contained in @slot. + * On successful return the guest sees a zero page so as to avoid + * leaking host data and the up-to-date flag is set. + */ +static int kvm_gmem_prepare_folio(struct file *file, struct kvm_memory_slot *slot, + gfn_t gfn, struct folio *folio) { - struct folio *folio; + unsigned long nr_pages, i; + pgoff_t index; + int r; - /* TODO: Support huge pages. */ - folio = filemap_grab_folio(inode->i_mapping, index); - if (IS_ERR(folio)) - return folio; + if (folio_test_uptodate(folio)) + return 0; + + nr_pages = folio_nr_pages(folio); + for (i = 0; i < nr_pages; i++) + clear_highpage(folio_page(folio, i)); /* - * Use the up-to-date flag to track whether or not the memory has been - * zeroed before being handed off to the guest. There is no backing - * storage for the memory, so the folio will remain up-to-date until - * it's removed. + * Preparing huge folios should always be safe, since it should + * be possible to split them later if needed. * - * TODO: Skip clearing pages when trusted firmware will do it when - * assigning memory to the guest. + * Right now the folio order is always going to be zero, but the + * code is ready for huge folios. The only assumption is that + * the base pgoff of memslots is naturally aligned with the + * requested page order, ensuring that huge folios can also use + * huge page table entries for GPA->HPA mapping. + * + * The order will be passed when creating the guest_memfd, and + * checked when creating memslots. */ - if (!folio_test_uptodate(folio)) { - unsigned long nr_pages = folio_nr_pages(folio); - unsigned long i; - - for (i = 0; i < nr_pages; i++) - clear_highpage(folio_page(folio, i)); - } - - if (prepare) { - int r = kvm_gmem_prepare_folio(inode, index, folio); - if (r < 0) { - folio_unlock(folio); - folio_put(folio); - return ERR_PTR(r); - } + WARN_ON(!IS_ALIGNED(slot->gmem.pgoff, 1 << folio_order(folio))); + index = gfn - slot->base_gfn + slot->gmem.pgoff; + index = ALIGN_DOWN(index, 1 << folio_order(folio)); + r = __kvm_gmem_prepare_folio(file_inode(file), index, folio); + if (!r) folio_mark_uptodate(folio); - } - /* - * Ignore accessed, referenced, and dirty flags. The memory is - * unevictable and there is no storage to write back to. - */ - return folio; + return r; +} + +/* + * Returns a locked folio on success. The caller is responsible for + * setting the up-to-date flag before the memory is mapped into the guest. + * There is no backing storage for the memory, so the folio will remain + * up-to-date until it's removed. + * + * Ignore accessed, referenced, and dirty flags. The memory is + * unevictable and there is no storage to write back to. + */ +static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index) +{ + /* TODO: Support huge pages. */ + return filemap_grab_folio(inode->i_mapping, index); } static void kvm_gmem_invalidate_begin(struct kvm_gmem *gmem, pgoff_t start, @@ -201,7 +215,7 @@ static long kvm_gmem_allocate(struct inode *inode, loff_t offset, loff_t len) break; } - folio = kvm_gmem_get_folio(inode, index, true); + folio = kvm_gmem_get_folio(inode, index); if (IS_ERR(folio)) { r = PTR_ERR(folio); break; @@ -555,7 +569,7 @@ void kvm_gmem_unbind(struct kvm_memory_slot *slot) /* Returns a locked folio on success. */ static struct folio * __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot, - gfn_t gfn, kvm_pfn_t *pfn, int *max_order, bool prepare) + gfn_t gfn, kvm_pfn_t *pfn, int *max_order) { pgoff_t index = gfn - slot->base_gfn + slot->gmem.pgoff; struct kvm_gmem *gmem = file->private_data; @@ -572,7 +586,7 @@ __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot, return ERR_PTR(-EIO); } - folio = kvm_gmem_get_folio(file_inode(file), index, prepare); + folio = kvm_gmem_get_folio(file_inode(file), index); if (IS_ERR(folio)) return folio; @@ -594,17 +608,25 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, { struct file *file = kvm_gmem_get_file(slot); struct folio *folio; + int r = 0; if (!file) return -EFAULT; - folio = __kvm_gmem_get_pfn(file, slot, gfn, pfn, max_order, true); - fput(file); - if (IS_ERR(folio)) - return PTR_ERR(folio); + folio = __kvm_gmem_get_pfn(file, slot, gfn, pfn, max_order); + if (IS_ERR(folio)) { + r = PTR_ERR(folio); + goto out; + } + r = kvm_gmem_prepare_folio(file, slot, gfn, folio); folio_unlock(folio); - return 0; + if (r < 0) + folio_put(folio); + +out: + fput(file); + return r; } EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn); @@ -643,7 +665,7 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long break; } - folio = __kvm_gmem_get_pfn(file, slot, gfn, &pfn, &max_order, false); + folio = __kvm_gmem_get_pfn(file, slot, gfn, &pfn, &max_order); if (IS_ERR(folio)) { ret = PTR_ERR(folio); break; |