Excerpts from Sean Christopherson's message of November 6, 2021 12:49 am: > +Juergen and Marc > > On Fri, Nov 05, 2021, Nicholas Piggin wrote: >> Increasing the max VCPUs on powerpc makes the kvm_arch member offset >> great enough that some assembly breaks due to addressing constants >> overflowing field widths. >> >> Moving the vcpus array to the end of struct kvm prevents this from >> happening. It has the side benefit that moving the large array out >> from the middle of the structure should help keep other commonly >> accessed fields in the same or adjacent cache lines. >> >> Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx> >> --- >> >> It would next be possible to now make this a dynamically sized array, >> and make the KVM_MAX_VCPUS more dynamic > > Marc has a mostly-baked series to use an xarray[1][2] that AFAICT would be well > received. That has my vote, assuming it can get into 5.16. Marc or Juergen, > are either of you actively working on that? > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=kvm-arm64/vcpu-xarray > [2] https://lkml.kernel.org/r/871r65wwk7.wl-maz@xxxxxxxxxx Seems like a good idea if it can allow vcpu structs to be allocated to preferred nodes. >> however x86 kvm_svm uses its own scheme rather than kvm_arch for some reason. > > What's the problem in kvm_svm? It embeds a struct kvm so it couldn't be variable sized. Thanks, Nick
