Re: [PATCH 0/8] KVM: SEV-ES: fixes for string I/O emulation

Sean Christopherson
2021-10-21T20:04:44Z

On Thu, Oct 21, 2021, Paolo Bonzini wrote:
> On 13/10/21 18:56, Paolo Bonzini wrote:
> > This series, namely patches 1 and 8, fix two bugs in string I/O
> > emulation for SEV-ES:
> >
> > - first, the length is completely off for "rep ins" and "rep outs"
> > operation of size > 1. After setup_vmgexit_scratch, svm->ghcb_sa_len
> > is in bytes, but kvm_sev_es_string_io expects the number of PIO
> > operations.
> >
> > - second, the size of the GHCB buffer can exceed the size of
> > vcpu->arch.pio_data. If that happens, we need to go over the GHCB
> > buffer in multiple passes.
> >
> > The second bug was reported by Felix Wilhelm. The first was found by
> > me by code inspection; on one hand it seems *too* egregious so I'll be
> > gladly proven wrong on this, on the other hand... I know I'm bad at code
> > review, but not _that_ bad.

String I/O was completely busted on the Linux guest side as well, I wouldn't be
the least bit surprised if KVM were completely broken as well (reviewing now...).