From c8c340a9b4149fe5caa433f3b62463a1c8e07a46 Mon Sep 17 00:00:00 2001 From: Masahiro Kozuka Date: Tue, 14 Sep 2021 14:09:51 -0700 Subject: [PATCH] KVM: SEV: Flush cache on non-coherent systems before RECEIVE_UPDATE_DATA Flush the destination page before invoking RECEIVE_UPDATE_DATA, as the PSP encrypts the data with the guest's key when writing to guest memory. If the target memory was not previously encrypted, the cache may contain dirty, unecrypted data that will persist on non-coherent systems. Fixes: 15fb7de1a7f5 ("KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command") Cc: stable@vger.kernel.org Cc: Peter Gonda Cc: Marc Orr Cc: Tom Lendacky Cc: Brijesh Singh Signed-off-by: Masahiro Kozuka [sean: converted bug report to changelog] Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini Message-Id: <20210914210951.2994260-3-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm/sev.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 0d21d59..2e4916b 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -1484,6 +1484,13 @@ static int sev_receive_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp) goto e_free_trans; } + /* + * Flush (on non-coherent CPUs) before RECEIVE_UPDATE_DATA, the PSP + * encrypts the written data with the guest's key, and the cache may + * contain dirty, unencrypted data. + */ + sev_clflush_pages(guest_page, n); + /* The RECEIVE_UPDATE_DATA command requires C-bit to be always set. */ data.guest_address = (page_to_pfn(guest_page[0]) << PAGE_SHIFT) + offset; data.guest_address |= sev_me_mask; -- 2.7.4