KVM: SVM: Fix offset computation bug in __sev_dbg_decrypt().

Fix offset computation in __sev_dbg_decrypt() to include the
source paddr before it is rounded down to be aligned to 16 bytes
as required by SEV API. This fixes incorrect guest memory dumps
observed when using qemu monitor.

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Message-Id: <20201110224205.29444-1-Ashish.Kalra@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index c0b14106258a7c84241fba9e7b94c2affbcf2cf1..566f4d18185b1d4bcd2573c0038f687b1b3fc29e 100644 (file)
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -642,8 +642,8 @@ static int __sev_dbg_decrypt(struct kvm *kvm, unsigned long src_paddr,
         * Its safe to read more than we are asked, caller should ensure that
         * destination has enough space.
         */
-       src_paddr = round_down(src_paddr, 16);
        offset = src_paddr & 15;
+       src_paddr = round_down(src_paddr, 16);
        sz = round_up(sz + offset, 16);
 
        return __sev_issue_dbg_cmd(kvm, src_paddr, dst_paddr, sz, err, false);