KVM: SVM: Issue WBINVD after deactivating an SEV guest (2e2409af) · Commits · 戴 / test

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 ("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: ("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>

arch/x86/kvm/svm.c

+14 −8

Original line number	Diff line number	Diff line
		@@ -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(&region->list);
		kfree(region);
		@@ -1970,6 +1962,13 @@ 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);

Admin message