[v1][KVM][PATCH 1/1] kvm:ppc:booehv: direct ISI exception to Guest

[Caraman Mihai Claudiu-B02008]

> -----Original Message-----
> From: kvm-owner at vger.kernel.org [mailto:kvm-owner at vger.kernel.org] On
> Behalf Of tiejun.chen
> Sent: Wednesday, May 08, 2013 4:54 AM
> To: Wood Scott-B07421
> Cc: agraf at suse.de; kvm-ppc at vger.kernel.org; kvm at vger.kernel.org;
> linuxppc-dev at lists.ozlabs.org
> Subject: Re: [v1][KVM][PATCH 1/1] kvm:ppc:booehv: direct ISI exception to
> Guest
> 
> On 05/08/2013 07:40 AM, Scott Wood wrote:
> > On 05/07/2013 06:06:30 AM, Tiejun Chen wrote:
> >> We also can direct ISI exception to Guest like DSI.
> >>
> >> Signed-off-by: Tiejun Chen <tiejun.chen at windriver.com>
> >> ---
> >>  arch/powerpc/kvm/booke_emulate.c |    3 +++
> >>  arch/powerpc/kvm/e500mc.c        |    3 ++-
> >>  2 files changed, 5 insertions(+), 1 deletion(-)
> >
> > Are you seeing a real performance improvement from this?  This will
> interfere
> 
> No. But after we reduce the exit to host, shouldn't this improve
> performance?

We lose some flexibility for this so it make sense only if we gain
measurable improvements.

> 
> > somewhat with using the VF bit, if we were to ever do so, since VF only
> affects
> 
> Sorry, what is the VF you said?

VF stands for virtualization fault see MAS8[VF] and we may use it for virtualized
MMIO. The hypervisor should deny execute access on pages marked with VF. Accordingly
in this case guest ISI exceptions should be handled by the hypervisor.

-Mike