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

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Date:   Thu, 21 Oct 2021 20:04:38 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        fwilhelm@...gle.com, oupton@...gle.com
Subject: Re: [PATCH 0/8] KVM: SEV-ES: fixes for string I/O emulation

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...).