Re: [PATCH] KVM: s390: Enable specification exception interpretation

[Christian Borntraeger]

On 07.07.21 10:56, Janis Schoetterl-Glausch wrote:
> On 7/7/21 10:30 AM, Christian Borntraeger wrote:
> > On 06.07.21 13:47, Janis Schoetterl-Glausch wrote:
> > > When this feature is enabled the hardware is free to interpret
> > > specification exceptions generated by the guest, instead of causing
> > > program interruption interceptions.
> > >
> > > This benefits (test) programs that generate a lot of specification
> > > exceptions (roughly 4x increase in exceptions/sec).
> > >
> > > Interceptions will occur as before if ICTL_PINT is set,
> > > i.e. if guest debug is enabled.
> >
> > I think I will add
> >
> > There is no indication if this feature is available or not and the hardware
> > is free to interpret or not. So we can simply set this bit and if the
> > hardware ignores it we fall back to intercept 8 handling.
>
> Might also mention vSIE and/or incorporate into first paragraph:
>
> When this feature is enabled the hardware is free to interpret
> specification exceptions generated by the guest, instead of causing
> program interruption interceptions, but it is not required to.
> There is no indication if this feature is available or not,
> so we can simply set this bit and if the hardware ignores it
> we fall back to intercept 8 handling.
> The same applies to vSIE, we forward the guest hypervisor's bit
> and fall back to injection if interpretation does not occur.

Can you maybe resend a v2 with all comments (and RBs) added?