RE: Ping: [PATCH v2 1/2] viridian: remove implicit limit of 64 VPs per partition

[Paul Durrant <xadimgnik@xxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: 29 January 2021 10:31
> To: paul@xxxxxxx; iwj@xxxxxxxxxxxxxx; wl@xxxxxxx; anthony.perard@xxxxxxxxxx
> Cc: andrew.cooper3@xxxxxxxxxx; george.dunlap@xxxxxxxxxx; julien@xxxxxxx; 
> sstabellini@xxxxxxxxxx;
> roger.pau@xxxxxxxxxx; xen-devel@xxxxxxxxxxxxxxxxxxxx; Igor Druzhinin 
> <igor.druzhinin@xxxxxxxxxx>
> Subject: Ping: [PATCH v2 1/2] viridian: remove implicit limit of 64 VPs per 
> partition
> 
> On 25.01.2021 16:37, Igor Druzhinin wrote:
> > On 12/01/2021 04:17, Igor Druzhinin wrote:
> >> TLFS 7.8.1 stipulates that "a virtual processor index must be less than
> >> the maximum number of virtual processors per partition" that "can be 
> >> obtained
> >> through CPUID leaf 0x40000005". Furthermore, "Requirements for Implementing
> >> the Microsoft Hypervisor Interface" defines that starting from Windows 
> >> Server
> >> 2012, which allowed more than 64 CPUs to be brought up, this leaf can now
> >> contain a value -1 basically assuming the hypervisor has no restriction 
> >> while
> >> 0 (that we currently expose) means the default restriction is still 
> >> present.
> >>
> >> Along with the previous changes exposing ExProcessorMasks this allows a 
> >> recent
> >> Windows VM with Viridian extension enabled to have more than 64 vCPUs 
> >> without
> >> going into BSOD in some cases.
> >>
> >> Since we didn't expose the leaf before and to keep CPUID data consistent 
> >> for
> >> incoming streams from previous Xen versions - let's keep it behind an 
> >> option.
> >>
> >> Signed-off-by: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>
> >> ---
> >
> > ping? Paul?
> 
> Paul - I saw a reply by you on patch 2, but not on this one.
> 

Oh sorry, yes. Done now.

  Paul

> libxl maintainers - both patches would want to be acked by you.
> 
> Jan