> -----Original Message----- > From: Igor Druzhinin <igor.druzhi...@citrix.com> > Sent: 12 January 2021 04:17 > To: xen-devel@lists.xenproject.org > Cc: i...@xenproject.org; w...@xen.org; andrew.coop...@citrix.com; > george.dun...@citrix.com; > jbeul...@suse.com; jul...@xen.org; sstabell...@kernel.org; > anthony.per...@citrix.com; p...@xen.org; > roger....@citrix.com; Igor Druzhinin <igor.druzhi...@citrix.com> > 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.druzhi...@citrix.com>
Reviewed-by: Paul Durrant <p...@xen.org>
