On Thu, Mar 01, 2018 at 05:01:55PM +0000, Roger Pau Monné wrote: > On Thu, Mar 01, 2018 at 04:01:23PM +0000, Wei Liu wrote: > > On Thu, Mar 01, 2018 at 03:57:18PM +0000, Andrew Cooper wrote: > > > On 01/03/18 12:22, Wei Liu wrote: > > > > On Wed, Feb 28, 2018 at 10:20:53AM +0000, Roger Pau Monne wrote: > > > >> XSA-256 forces the local APIC to always be enabled for PVH guests, so > > > >> ignore any apic option for PVH guests. Update the documentation > > > >> accordingly. > > > > I think how I will approach this is to dictate that PVH always has LAPIC > > > > in our in-tree document, then use that as the justification for this > > > > change. That's the consensus from 2 years ago, right? > > > > > > > > Or we're just working around the limitation in our code base, and users > > > > may demand a no-LAPIC PVH guest just because... > > > > > > Currently, Xen enforces that HVM guests have an LAPIC. This is because > > > making the non-LAPIC case function correctly/safely devolved into a > > > massive rats nest and I stopped trying to fix it after 2 days of trying. > > > > > > At the moment, it would be wise to discuss whether the non-LAPIC case is > > > actually sensible. I personally see no value in keeping it. > > > > > > > +1 > > > > > If someone can come up with a convincing usecase for keeping it, then > > > ok, but the barrier for this is increasing all the time, especially now > > > that hardware acceleration and posted interrupts means that a > > > pipeline-virtualised APIC is faster and more efficient than any of our > > > event channel mechanisms. > > > > +1 > > I've looked at the in-tree pvh document and it just refers to the local > APIC in this sentence: > > "AP startup can be performed using hypercalls or the local APIC if present." > > I guess the trailing "if present" could be removed, but it's not > colliding with this patch. > > I'm happy with rebasing this patch and applying the above change, is > there any other document that should be changed?
Can we make it more explicit. Like VCPUs for PVH must have local APIC and it can't be disabled. ? (CC Jan as well) Wei. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
