diff options
| author | Sean Christopherson <seanjc@google.com> | 2026-09-28 08:46:44 -0700 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2026-09-28 17:11:49 -0400 |
| commit | 973ea70393e885e540f714904e51bc6cac80e3d7 (patch) | |
| tree | c65b2061b7d461b1697a1fe4956c53b25a5c4bfd /arch/x86 | |
| parent | 8abbc76120a74bfba1851bd97528099d715e45c6 (diff) | |
KVM: SEV: Do cache maintenance on the source VM *before* clearing SEV state
Explicitly flush caches after intra-host migration before clearing "SEV
active" on the source VM, as doing cache maintenance afterwards creates a
tiny window where memory reclaim could return memory to the host without
performing a cache flush, e.g. as pointed out by Sashiko:
CPU1 in sev_migrate_from():
src->active = false;
CPU2 running concurrent unmap:
Since active is false, the automatic cache flush in
sev_guest_memory_reclaimed is skipped.
The host frees and reallocates the page.
CPU1 in sev_migrate_from():
sev_writeback_caches(src_kvm);
Executes a hardware cache flush (wbnoinvd), which writes the guest's old
dirty ciphertext over the new page owner's data.
Fixes: 93de2a6a4b91 ("KVM: SEV: Do cache maintenance on the source VM during intra-host migration")
Cc: stable@vger.kernel.org
Reported-by: Sashiko Bot <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/all/20260923165304.1662E1F000FF@smtp.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260928154644.2559454-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kvm/svm/sev.c | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index d3a2e6a51efc..0c1ebb16cec6 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -2045,6 +2045,13 @@ static void sev_migrate_from(struct kvm *dst_kvm, struct kvm *src_kvm) struct kvm_sev_info *mirror; unsigned long i; + /* + * Do cache maintenance on the source VM *before* clearing "SEV active", + * as memory reclaim flows won't trigger cache maintenance on the VM + * once it's no longer an SEV VM. + */ + sev_writeback_caches(src_kvm); + dst->active = true; dst->asid = src->asid; dst->handle = src->handle; @@ -2058,12 +2065,6 @@ static void sev_migrate_from(struct kvm *dst_kvm, struct kvm *src_kvm) src->pages_locked = 0; src->es_active = false; - /* - * Do cache maintenance on the source VM as it is no longer an SEV VM, - * i.e. memory reclaim flows won't trigger cache maintenance on the VM. - */ - sev_writeback_caches(src_kvm); - list_cut_before(&dst->regions_list, &src->regions_list, &src->regions_list); mutex_lock(&sev_mirror_lock); |