lkml.org 
[lkml]   [2015]   [Jan]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [v3 13/26] KVM: Define a new interface kvm_find_dest_vcpu() for VT-d PI
2015-01-09 15:56+0100, Paolo Bonzini:
>
>
> On 09/01/2015 15:54, Radim Krčmář wrote:
> > There are two points relevant to this patch in new KVM's implementation,
> > ("KVM: x86: amend APIC lowest priority arbitration",
> > https://lkml.org/lkml/2015/1/9/362)
> >
> > 1) lowest priority depends on TPR
> > 2) there is no need for balancing
> >
> > (1) has to be considered with PI as well.
>
> The chipset doesn't support it. :(

I meant that we need to recompute PI entries for lowest priority
interrupts every time guest's TPR changes.

Luckily, Linux doesn't use TPR, but other OS might be a reason to drop
lowest priority from PI optimizations. (Or make it more complicated.)

> > I kept (2) to avoid whining from people building on that behaviour, but
> > lowest priority backed by PI could be transparent without it.
> >
> > Patch below removes the balancing, but I am not sure this is a price we
> > allowed ourselves to pay ... what are your opinions?
>
> I wouldn't mind, but it requires a lot of benchmarking.

(I was afraid it would come to that.)


\
 
 \ /
  Last update: 2015-01-09 16:21    [W:0.506 / U:0.028 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site