(re-adding xen-devel@) On 23.07.2024 14:57, Matthew Barnes wrote: > On Mon, Jul 22, 2024 at 01:37:11PM +0200, Jan Beulich wrote: >> On 19.07.2024 16:21, Matthew Barnes wrote: >>> Currently, OVMF is hard-coded to set up a maximum of 64 vCPUs on >>> startup. >>> >>> There are efforts to support a maximum of 128 vCPUs, which would involve >>> bumping the OVMF constant from 64 to 128. >>> >>> However, it would be more future-proof for OVMF to access the maximum >>> number of vCPUs for a domain and set itself up appropriately at >>> run-time. >>> >>> GitLab ticket: https://gitlab.com/xen-project/xen/-/issues/191 >>> >>> For OVMF to access the maximum vCPU count, this patch has Xen expose >>> the maximum vCPU ID via cpuid on the HVM hypervisor leaf in edx. >>> >>> Signed-off-by: Matthew Barnes <matthew.bar...@cloud.com> >>> --- >>> Changes in v2: >>> - Tweak value from "maximum vcpu count" to "maximum vcpu id" >>> - Reword commit message to avoid "have to" wording >>> - Fix vpcus -> vcpus typo >>> --- >> >> Yet still HVM-only? > > This field is only used when the guest is HVM, so I decided it should > only be present to HVM guests. > > If not, where else would you suggest to put this field?
In a presently unused leaf? Or one of the unused registers of leaf x01 (with the gating flag in leaf x02 ECX)? Jan
