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 --- drivers/md/dm-pcache/segment.c | 61 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) create mode 100644 drivers/md/dm-pcache/segment.c (limited to 'drivers/md/dm-pcache/segment.c') diff --git a/drivers/md/dm-pcache/segment.c b/drivers/md/dm-pcache/segment.c new file mode 100644 index 000000000..8f8816e1c --- /dev/null +++ b/drivers/md/dm-pcache/segment.c @@ -0,0 +1,61 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +#include + +#include "pcache_internal.h" +#include "cache_dev.h" +#include "segment.h" + +int segment_copy_to_bio(struct pcache_segment *segment, + u32 data_off, u32 data_len, struct bio *bio, u32 bio_off) +{ + struct iov_iter iter; + size_t copied; + void *src; + + iov_iter_bvec(&iter, ITER_DEST, &bio->bi_io_vec[bio->bi_iter.bi_idx], + bio_segments(bio), bio->bi_iter.bi_size); + iter.iov_offset = bio->bi_iter.bi_offset; + if (bio_off) + iov_iter_advance(&iter, bio_off); + + src = segment->data + data_off; + copied = _copy_mc_to_iter(src, data_len, &iter); + if (copied != data_len) + return -EIO; + + return 0; +} + +int segment_copy_from_bio(struct pcache_segment *segment, + u32 data_off, u32 data_len, struct bio *bio, u32 bio_off) +{ + struct iov_iter iter; + size_t copied; + void *dst; + + iov_iter_bvec(&iter, ITER_SOURCE, &bio->bi_io_vec[bio->bi_iter.bi_idx], + bio_segments(bio), bio->bi_iter.bi_size); + iter.iov_offset = bio->bi_iter.bi_offset; + if (bio_off) + iov_iter_advance(&iter, bio_off); + + dst = segment->data + data_off; + copied = _copy_from_iter_flushcache(dst, data_len, &iter); + if (copied != data_len) + return -EIO; + pmem_wmb(); + + return 0; +} + +void pcache_segment_init(struct pcache_cache_dev *cache_dev, struct pcache_segment *segment, + struct pcache_segment_init_options *options) +{ + segment->seg_info = options->seg_info; + segment_info_set_type(segment->seg_info, options->type); + + segment->cache_dev = cache_dev; + segment->seg_id = options->seg_id; + segment->data_size = PCACHE_SEG_SIZE - options->data_off; + segment->data = CACHE_DEV_SEGMENT(cache_dev, options->seg_id) + options->data_off; +} -- cgit v1.3.1