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 --- tools/testing/radix-tree/regression3.c | 95 ++++++++++++++++++++++++++++++++++ 1 file changed, 95 insertions(+) create mode 100644 tools/testing/radix-tree/regression3.c (limited to 'tools/testing/radix-tree/regression3.c') diff --git a/tools/testing/radix-tree/regression3.c b/tools/testing/radix-tree/regression3.c new file mode 100644 index 000000000..9f9a3b280 --- /dev/null +++ b/tools/testing/radix-tree/regression3.c @@ -0,0 +1,95 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Regression3 + * Description: + * Helper radix_tree_iter_retry resets next_index to the current index. + * In following radix_tree_next_slot current chunk size becomes zero. + * This isn't checked and it tries to dereference null pointer in slot. + * + * Helper radix_tree_iter_resume reset slot to NULL and next_index to index + 1, + * for tagger iteraction it also must reset cached tags in iterator to abort + * next radix_tree_next_slot and go to slow-path into radix_tree_next_chunk. + * + * Running: + * This test should run to completion immediately. The above bug would + * cause it to segfault. + * + * Upstream commit: + * Not yet + */ +#include +#include +#include +#include +#include +#include + +#include "regression.h" + +void regression3_test(void) +{ + RADIX_TREE(root, GFP_KERNEL); + void *ptr0 = (void *)4ul; + void *ptr = (void *)8ul; + struct radix_tree_iter iter; + void **slot; + bool first; + + printv(1, "running regression test 3 (should take milliseconds)\n"); + + radix_tree_insert(&root, 0, ptr0); + radix_tree_tag_set(&root, 0, 0); + + first = true; + radix_tree_for_each_tagged(slot, &root, &iter, 0, 0) { + printv(2, "tagged %ld %p\n", iter.index, *slot); + if (first) { + radix_tree_insert(&root, 1, ptr); + radix_tree_tag_set(&root, 1, 0); + first = false; + } + if (radix_tree_deref_retry(*slot)) { + printv(2, "retry at %ld\n", iter.index); + slot = radix_tree_iter_retry(&iter); + continue; + } + } + radix_tree_delete(&root, 1); + + first = true; + radix_tree_for_each_slot(slot, &root, &iter, 0) { + printv(2, "slot %ld %p\n", iter.index, *slot); + if (first) { + radix_tree_insert(&root, 1, ptr); + first = false; + } + if (radix_tree_deref_retry(*slot)) { + printv(2, "retry at %ld\n", iter.index); + slot = radix_tree_iter_retry(&iter); + continue; + } + } + + radix_tree_for_each_slot(slot, &root, &iter, 0) { + printv(2, "slot %ld %p\n", iter.index, *slot); + if (!iter.index) { + printv(2, "next at %ld\n", iter.index); + slot = radix_tree_iter_resume(slot, &iter); + } + } + + radix_tree_tag_set(&root, 0, 0); + radix_tree_tag_set(&root, 1, 0); + radix_tree_for_each_tagged(slot, &root, &iter, 0, 0) { + printv(2, "tagged %ld %p\n", iter.index, *slot); + if (!iter.index) { + printv(2, "next at %ld\n", iter.index); + slot = radix_tree_iter_resume(slot, &iter); + } + } + + radix_tree_delete(&root, 0); + radix_tree_delete(&root, 1); + + printv(1, "regression test 3 passed\n"); +} -- cgit v1.3.1