On Wed, Oct 13, 2021 at 9:56 AM Paolo Bonzini pbonzini@redhat.com wrote:
The size of the data in the scratch buffer is not divided by the size of each port I/O operation, so vcpu->arch.pio.count ends up being larger than it should be by a factor of size.
Cc: stable@vger.kernel.org Fixes: 7ed9abfe8e9f ("KVM: SVM: Support string IO operations for an SEV-ES guest") Signed-off-by: Paolo Bonzini pbonzini@redhat.com
arch/x86/kvm/svm/sev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index c36b5fe4c27c..e672493b5d8d 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -2583,7 +2583,7 @@ int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in) return -EINVAL;
return kvm_sev_es_string_io(&svm->vcpu, size, port,
svm->ghcb_sa, svm->ghcb_sa_len, in);
svm->ghcb_sa, svm->ghcb_sa_len / size, in);}
void sev_es_init_vmcb(struct vcpu_svm *svm)
2.27.0
I could be missing something, but I'm pretty sure that this is wrong. The GHCB spec says that `exit_info_2` is the `rep` count. Not the string length.
For example, given a `rep outsw` instruction, with `ECX` set to `8`, the rep count written into `SW_EXITINFO2` should be eight x86 words (i.e., 16 bytes) and the IO size should be one x86 word (i.e., 2 bytes). In other words, the code was correct before this patch. This patch is incorrectly dividing the rep count by the IO size, causing the string IO to be truncated.