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/zstd_wrapper.c | 154 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 154 insertions(+) create mode 100644 fs/squashfs/zstd_wrapper.c (limited to 'fs/squashfs/zstd_wrapper.c') diff --git a/fs/squashfs/zstd_wrapper.c b/fs/squashfs/zstd_wrapper.c new file mode 100644 index 000000000..487fbc51d --- /dev/null +++ b/fs/squashfs/zstd_wrapper.c @@ -0,0 +1,154 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Squashfs - a compressed read only filesystem for Linux + * + * Copyright (c) 2016-present, Facebook, Inc. + * All rights reserved. + * + * zstd_wrapper.c + */ + +#include +#include +#include +#include +#include + +#include "squashfs_fs.h" +#include "squashfs_fs_sb.h" +#include "squashfs.h" +#include "decompressor.h" +#include "page_actor.h" + +struct workspace { + void *mem; + size_t mem_size; + size_t window_size; +}; + +static void *zstd_init(struct squashfs_sb_info *msblk, void *buff) +{ + struct workspace *wksp = kmalloc_obj(*wksp); + + if (wksp == NULL) + goto failed; + wksp->window_size = max_t(size_t, + msblk->block_size, SQUASHFS_METADATA_SIZE); + wksp->mem_size = zstd_dstream_workspace_bound(wksp->window_size); + wksp->mem = vmalloc(wksp->mem_size); + if (wksp->mem == NULL) + goto failed; + + return wksp; + +failed: + ERROR("Failed to allocate zstd workspace\n"); + kfree(wksp); + return ERR_PTR(-ENOMEM); +} + + +static void zstd_free(void *strm) +{ + struct workspace *wksp = strm; + + if (wksp) + vfree(wksp->mem); + kfree(wksp); +} + + +static int zstd_uncompress(struct squashfs_sb_info *msblk, void *strm, + struct bio *bio, int offset, int length, + struct squashfs_page_actor *output) +{ + struct workspace *wksp = strm; + zstd_dstream *stream; + size_t total_out = 0; + int error = 0; + zstd_in_buffer in_buf = { NULL, 0, 0 }; + zstd_out_buffer out_buf = { NULL, 0, 0 }; + struct bvec_iter_all iter_all = {}; + struct bio_vec *bvec = bvec_init_iter_all(&iter_all); + + stream = zstd_init_dstream(wksp->window_size, wksp->mem, wksp->mem_size); + + if (!stream) { + ERROR("Failed to initialize zstd decompressor\n"); + return -EIO; + } + + out_buf.size = PAGE_SIZE; + out_buf.dst = squashfs_first_page(output); + if (IS_ERR(out_buf.dst)) { + error = PTR_ERR(out_buf.dst); + goto finish; + } + + for (;;) { + size_t zstd_err; + + if (in_buf.pos == in_buf.size) { + const void *data; + int avail; + + if (!bio_next_segment(bio, &iter_all)) { + error = -EIO; + break; + } + + avail = min(length, ((int)bvec->bv_len) - offset); + data = bvec_virt(bvec); + length -= avail; + in_buf.src = data + offset; + in_buf.size = avail; + in_buf.pos = 0; + offset = 0; + } + + if (out_buf.pos == out_buf.size) { + out_buf.dst = squashfs_next_page(output); + if (IS_ERR(out_buf.dst)) { + error = PTR_ERR(out_buf.dst); + break; + } else if (out_buf.dst == NULL) { + /* Shouldn't run out of pages + * before stream is done. + */ + error = -EIO; + break; + } + out_buf.pos = 0; + out_buf.size = PAGE_SIZE; + } + + total_out -= out_buf.pos; + zstd_err = zstd_decompress_stream(stream, &out_buf, &in_buf); + total_out += out_buf.pos; /* add the additional data produced */ + if (zstd_err == 0) + break; + + if (zstd_is_error(zstd_err)) { + ERROR("zstd decompression error: %d\n", + (int)zstd_get_error_code(zstd_err)); + error = -EIO; + break; + } + } + +finish: + + squashfs_finish_page(output); + + return error ? error : total_out; +} + +const struct squashfs_decompressor squashfs_zstd_comp_ops = { + .init = zstd_init, + .free = zstd_free, + .decompress = zstd_uncompress, + .id = ZSTD_COMPRESSION, + .name = "zstd", + .alloc_buffer = 1, + .supported = 1 +}; -- cgit v1.3.1