From 93de2a6a4b91b72607136dd656edf03fb399d27f Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 23 Sep 2026 09:37:21 -0700 Subject: KVM: SEV: Do cache maintenance on the source VM during intra-host migration Manually perform cache maintenance on the source VM during intra-host migration to ensure no stale data is left in CPU caches after the VM is destroyed. Because the source VM is "converted" to a non-SEV VM, KVM's memory reclaim flows won't trigger cache maintenance, e.g. when all guest memory is reclaimed in response to detaching from the mmu_notifier. Note, relying on the destination VM to do cache maintenance isn't an option as KVM doesn't require identical guest memory configurations, i.e. the source VM may have access to memory that the destination VM does not. Enforcing equivalent memory configurations is infeasible, as it would require a *deep* comparison of memslots, e.g. to verify that not only are the memslot identical, but what the memslots point at is also identical. Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration") Cc: stable@vger.kernel.org Reported-by: Stefan Teodorescu Signed-off-by: Sean Christopherson Message-ID: <20260923163721.1584779-3-seanjc@google.com> Signed-off-by: Paolo Bonzini --- fs/squashfs/block.c | 386 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 386 insertions(+) create mode 100644 fs/squashfs/block.c (limited to 'fs/squashfs/block.c') diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c new file mode 100644 index 000000000..2d5850168 --- /dev/null +++ b/fs/squashfs/block.c @@ -0,0 +1,386 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Squashfs - a compressed read only filesystem for Linux + * + * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 + * Phillip Lougher + * + * block.c + */ + +/* + * This file implements the low-level routines to read and decompress + * datablocks and metadata blocks. + */ + +#include +#include +#include +#include +#include +#include +#include + +#include "squashfs_fs.h" +#include "squashfs_fs_sb.h" +#include "squashfs.h" +#include "decompressor.h" +#include "page_actor.h" + +/* + * Returns the amount of bytes copied to the page actor. + */ +static int copy_bio_to_actor(struct bio *bio, + struct squashfs_page_actor *actor, + int offset, int req_length) +{ + void *actor_addr; + struct bvec_iter_all iter_all = {}; + struct bio_vec *bvec = bvec_init_iter_all(&iter_all); + int copied_bytes = 0; + int actor_offset = 0; + + squashfs_actor_nobuff(actor); + actor_addr = squashfs_first_page(actor); + + if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) + return 0; + + while (copied_bytes < req_length) { + int bytes_to_copy = min_t(int, bvec->bv_len - offset, + PAGE_SIZE - actor_offset); + + bytes_to_copy = min_t(int, bytes_to_copy, + req_length - copied_bytes); + if (!IS_ERR(actor_addr)) + memcpy(actor_addr + actor_offset, bvec_virt(bvec) + + offset, bytes_to_copy); + + actor_offset += bytes_to_copy; + copied_bytes += bytes_to_copy; + offset += bytes_to_copy; + + if (actor_offset >= PAGE_SIZE) { + actor_addr = squashfs_next_page(actor); + if (!actor_addr) + break; + actor_offset = 0; + } + if (offset >= bvec->bv_len) { + if (!bio_next_segment(bio, &iter_all)) + break; + offset = 0; + } + } + squashfs_finish_page(actor); + return copied_bytes; +} + +static int squashfs_bio_read_cached(struct bio *fullbio, + struct address_space *cache_mapping, u64 index, int length, + u64 read_start, u64 read_end, int page_count) +{ + struct folio *head_to_cache = NULL, *tail_to_cache = NULL; + struct block_device *bdev = fullbio->bi_bdev; + int start_idx = 0, end_idx = 0; + struct folio_iter fi; + struct bio *bio = NULL; + int idx = 0; + int err = 0; +#ifdef CONFIG_SQUASHFS_COMP_CACHE_FULL + struct folio **cache_folios = kmalloc_objs(*cache_folios, page_count, + GFP_KERNEL | __GFP_ZERO); +#endif + + bio_for_each_folio_all(fi, fullbio) { + struct folio *folio = fi.folio; + + if (folio->mapping == cache_mapping) { + idx++; + continue; + } + + /* + * We only use this when the device block size is the same as + * the page size, so read_start and read_end cover full pages. + * + * Compare these to the original required index and length to + * only cache pages which were requested partially, since these + * are the ones which are likely to be needed when reading + * adjacent blocks. + */ + if (idx == 0 && index != read_start) + head_to_cache = folio; + else if (idx == page_count - 1 && index + length != read_end) + tail_to_cache = folio; +#ifdef CONFIG_SQUASHFS_COMP_CACHE_FULL + /* Cache all pages in the BIO for repeated reads */ + else if (cache_folios) + cache_folios[idx] = folio; +#endif + + if (!bio || idx != end_idx) { + struct bio *new = bio_alloc_clone(bdev, fullbio, + GFP_NOIO, &fs_bio_set); + + if (bio) { + bio_trim(bio, start_idx * PAGE_SECTORS, + (end_idx - start_idx) * PAGE_SECTORS); + bio_chain(bio, new); + submit_bio(bio); + } + + bio = new; + start_idx = idx; + } + + idx++; + end_idx = idx; + } + + if (bio) { + bio_trim(bio, start_idx * PAGE_SECTORS, + (end_idx - start_idx) * PAGE_SECTORS); + err = submit_bio_wait(bio); + bio_put(bio); + } + + if (err) + return err; + + if (head_to_cache) { + int ret = filemap_add_folio(cache_mapping, head_to_cache, + read_start >> PAGE_SHIFT, + GFP_NOIO); + + if (!ret) { + folio_mark_uptodate(head_to_cache); + folio_unlock(head_to_cache); + } + + } + + if (tail_to_cache) { + int ret = filemap_add_folio(cache_mapping, tail_to_cache, + (read_end >> PAGE_SHIFT) - 1, + GFP_NOIO); + + if (!ret) { + folio_mark_uptodate(tail_to_cache); + folio_unlock(tail_to_cache); + } + } + +#ifdef CONFIG_SQUASHFS_COMP_CACHE_FULL + if (!cache_folios) + goto out; + + for (idx = 0; idx < page_count; idx++) { + if (!cache_folios[idx]) + continue; + int ret = filemap_add_folio(cache_mapping, cache_folios[idx], + (read_start >> PAGE_SHIFT) + idx, + GFP_NOIO); + + if (!ret) { + folio_mark_uptodate(cache_folios[idx]); + folio_unlock(cache_folios[idx]); + } + } + kfree(cache_folios); +out: +#endif + return 0; +} + +static struct page *squashfs_get_cache_page(struct address_space *mapping, + pgoff_t index) +{ + struct page *page; + + if (!mapping) + return NULL; + + page = find_get_page(mapping, index); + if (!page) + return NULL; + + if (!PageUptodate(page)) { + put_page(page); + return NULL; + } + + return page; +} + +static int squashfs_bio_read(struct super_block *sb, u64 index, int length, + struct bio **biop, int *block_offset) +{ + struct squashfs_sb_info *msblk = sb->s_fs_info; + struct address_space *cache_mapping = msblk->cache_mapping; + const u64 read_start = round_down(index, msblk->devblksize); + const sector_t block = read_start >> msblk->devblksize_log2; + const u64 read_end = round_up(index + length, msblk->devblksize); + const sector_t block_end = read_end >> msblk->devblksize_log2; + int offset = read_start - round_down(index, PAGE_SIZE); + int total_len = (block_end - block) << msblk->devblksize_log2; + const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE); + int error, i; + struct bio *bio; + + bio = bio_kmalloc(page_count, GFP_NOIO); + if (!bio) + return -ENOMEM; + bio_init_inline(bio, sb->s_bdev, page_count, REQ_OP_READ); + bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT); + + for (i = 0; i < page_count; ++i) { + unsigned int len = + min_t(unsigned int, PAGE_SIZE - offset, total_len); + pgoff_t index = (read_start >> PAGE_SHIFT) + i; + struct page *page; + + page = squashfs_get_cache_page(cache_mapping, index); + if (!page) + page = alloc_page(GFP_NOIO); + + if (!page) { + error = -ENOMEM; + goto out_free_bio; + } + + /* + * Use the __ version to avoid merging since we need each page + * to be separate when we check for and avoid cached pages. + */ + __bio_add_page(bio, page, len, offset); + offset = 0; + total_len -= len; + } + + if (cache_mapping) + error = squashfs_bio_read_cached(bio, cache_mapping, index, + length, read_start, read_end, + page_count); + else + error = submit_bio_wait(bio); + if (error) + goto out_free_bio; + + *biop = bio; + *block_offset = index & ((1 << msblk->devblksize_log2) - 1); + return 0; + +out_free_bio: + bio_free_pages(bio); + bio_uninit(bio); + kfree(bio); + return error; +} + +/* + * Read and decompress a metadata block or datablock. Length is non-zero + * if a datablock is being read (the size is stored elsewhere in the + * filesystem), otherwise the length is obtained from the first two bytes of + * the metadata block. A bit in the length field indicates if the block + * is stored uncompressed in the filesystem (usually because compression + * generated a larger block - this does occasionally happen with compression + * algorithms). + */ +int squashfs_read_data(struct super_block *sb, u64 index, int length, + u64 *next_index, struct squashfs_page_actor *output) +{ + struct squashfs_sb_info *msblk = sb->s_fs_info; + struct bio *bio = NULL; + int compressed; + int res; + int offset; + + if (length) { + /* + * Datablock. + */ + compressed = SQUASHFS_COMPRESSED_BLOCK(length); + length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length); + TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n", + index, compressed ? "" : "un", length, output->length); + } else { + /* + * Metadata block. + */ + const u8 *data; + struct bvec_iter_all iter_all = {}; + struct bio_vec *bvec = bvec_init_iter_all(&iter_all); + + if (index + 2 > msblk->bytes_used) { + res = -EIO; + goto out; + } + res = squashfs_bio_read(sb, index, 2, &bio, &offset); + if (res) + goto out; + + if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { + res = -EIO; + goto out_free_bio; + } + /* Extract the length of the metadata block */ + data = bvec_virt(bvec); + length = data[offset]; + if (offset < bvec->bv_len - 1) { + length |= data[offset + 1] << 8; + } else { + if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { + res = -EIO; + goto out_free_bio; + } + data = bvec_virt(bvec); + length |= data[0] << 8; + } + bio_free_pages(bio); + bio_uninit(bio); + kfree(bio); + + compressed = SQUASHFS_COMPRESSED(length); + length = SQUASHFS_COMPRESSED_SIZE(length); + index += 2; + + TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2, + compressed ? "" : "un", length); + } + if (length <= 0 || length > output->length || + (index + length) > msblk->bytes_used) { + res = -EIO; + goto out; + } + + if (next_index) + *next_index = index + length; + + res = squashfs_bio_read(sb, index, length, &bio, &offset); + if (res) + goto out; + + if (compressed) { + if (!msblk->stream) { + res = -EIO; + goto out_free_bio; + } + res = msblk->thread_ops->decompress(msblk, bio, offset, length, output); + } else { + res = copy_bio_to_actor(bio, output, offset, length); + } + +out_free_bio: + bio_free_pages(bio); + bio_uninit(bio); + kfree(bio); +out: + if (res < 0) { + ERROR("Failed to read block 0x%llx: %d\n", index, res); + if (msblk->panic_on_errors) + panic("squashfs read failed"); + } + + return res; +} -- cgit v1.3.1