[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [PATCH v2 1/2] viridian: remove implicit limit of 64 VPs per partition
> -----Original Message----- > From: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx> > Sent: 12 January 2021 04:17 > To: xen-devel@xxxxxxxxxxxxxxxxxxxx > Cc: iwj@xxxxxxxxxxxxxx; wl@xxxxxxx; andrew.cooper3@xxxxxxxxxx; > george.dunlap@xxxxxxxxxx; > jbeulich@xxxxxxxx; julien@xxxxxxx; sstabellini@xxxxxxxxxx; > anthony.perard@xxxxxxxxxx; paul@xxxxxxx; > roger.pau@xxxxxxxxxx; Igor Druzhinin <igor.druzhinin@xxxxxxxxxx> > Subject: [PATCH v2 1/2] viridian: remove implicit limit of 64 VPs per > partition > > 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> Reviewed-by: Paul Durrant <paul@xxxxxxx>
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