diff options
author | Tom Lendacky <thomas.lendacky@amd.com> | 2020-03-20 17:07:07 +0100 |
---|---|---|
committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-03-23 14:01:04 +0100 |
commit | 2e2409afe5f0c284c7dfe5504058e8d115806a7d (patch) | |
tree | e1937efd10e18ce5c6d3d32142eeb40f359e4ea2 /arch/x86/kvm/svm.c | |
parent | KVM: SVM: document KVM_MEM_ENCRYPT_OP, let userspace detect if SEV is available (diff) | |
download | linux-2e2409afe5f0c284c7dfe5504058e8d115806a7d.tar.xz linux-2e2409afe5f0c284c7dfe5504058e8d115806a7d.zip |
KVM: SVM: Issue WBINVD after deactivating an SEV guest
Currently, CLFLUSH is used to flush SEV guest memory before the guest is
terminated (or a memory hotplug region is removed). However, CLFLUSH is
not enough to ensure that SEV guest tagged data is flushed from the cache.
With 33af3a7ef9e6 ("KVM: SVM: Reduce WBINVD/DF_FLUSH invocations"), the
original WBINVD was removed. This then exposed crashes at random times
because of a cache flush race with a page that had both a hypervisor and
a guest tag in the cache.
Restore the WBINVD when destroying an SEV guest and add a WBINVD to the
svm_unregister_enc_region() function to ensure hotplug memory is flushed
when removed. The DF_FLUSH can still be avoided at this point.
Fixes: 33af3a7ef9e6 ("KVM: SVM: Reduce WBINVD/DF_FLUSH invocations")
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Message-Id: <c8bf9087ca3711c5770bdeaafa3e45b717dc5ef4.1584720426.git.thomas.lendacky@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/svm.c')
-rw-r--r-- | arch/x86/kvm/svm.c | 22 |
1 files changed, 14 insertions, 8 deletions
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index f0aa9ff9666f..50d1ebafe0b3 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1933,14 +1933,6 @@ static void sev_clflush_pages(struct page *pages[], unsigned long npages) static void __unregister_enc_region_locked(struct kvm *kvm, struct enc_region *region) { - /* - * The guest may change the memory encryption attribute from C=0 -> C=1 - * or vice versa for this memory range. Lets make sure caches are - * flushed to ensure that guest data gets written into memory with - * correct C-bit. - */ - sev_clflush_pages(region->pages, region->npages); - sev_unpin_memory(kvm, region->pages, region->npages); list_del(®ion->list); kfree(region); @@ -1971,6 +1963,13 @@ static void sev_vm_destroy(struct kvm *kvm) mutex_lock(&kvm->lock); /* + * Ensure that all guest tagged cache entries are flushed before + * releasing the pages back to the system for use. CLFLUSH will + * not do this, so issue a WBINVD. + */ + wbinvd_on_all_cpus(); + + /* * if userspace was terminated before unregistering the memory regions * then lets unpin all the registered memory. */ @@ -7288,6 +7287,13 @@ static int svm_unregister_enc_region(struct kvm *kvm, goto failed; } + /* + * Ensure that all guest tagged cache entries are flushed before + * releasing the pages back to the system for use. CLFLUSH will + * not do this, so issue a WBINVD. + */ + wbinvd_on_all_cpus(); + __unregister_enc_region_locked(kvm, region); mutex_unlock(&kvm->lock); |