From 6697ceb9f6cdab9bd3baddf5493dc4acde9a4508 Mon Sep 17 00:00:00 2001
From: Masahiro Kozuka <masa.koz@kozuka.jp>
Date: Tue, 14 Sep 2021 14:09:51 -0700
Subject: [PATCH] KVM: SEV: Flush cache on non-coherent systems before RECEIVE_UPDATE_DATA
Git-commit: c8c340a9b4149fe5caa433f3b62463a1c8e07a46
Patch-mainline: v5.15-rc7
References: stable-5.14.15
commit c8c340a9b4149fe5caa433f3b62463a1c8e07a46 upstream.
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 <pgonda@google.com>
Cc: Marc Orr <marcorr@google.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Masahiro Kozuka <masa.koz@kozuka.jp>
[sean: converted bug report to changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: <20210914210951.2994260-3-seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
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 cb166bde449b..4fd8ae3d4915 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1480,6 +1480,13 @@ 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;
--
2.26.2