On Thu, Oct 15, 2020 at 03:57:02PM +0100, Peter Maydell wrote: > On Thu, 15 Oct 2020 at 15:41, Andrew Jones <drjones@xxxxxxxxxx> wrote: > > The reporter states neither the source nor destination hardware supports > > SVE. My guess is that what's happening is the reserved ID register > > ID_UNALLOCATED(4,4) was showing up in the KVM_GET_REG_LIST count on > > the old kernel, but the new kernel filters it out. Maybe it is a > > bug to filter it out of the count, as it's a reserved ID register and > > I suppose the other reserved ID registers are still showing up? > > Yeah, RES0 ID registers should show up in the list, because otherwise > userspace has to annoyingly special case them when the architecture > eventually defines behaviour for them. > > Dave's comment in the kernel commit message > # ID_AA64ZFR0_EL1 is RO-RAZ for MRS/MSR when SVE is disabled for the > # guest, but for compatibility with non-SVE aware KVM implementations > # the register should not be enumerated at all for KVM_GET_REG_LIST > # in this case. > seems wrong to me -- for compatibility the register should remain > present and behave as RAZ/WI if SVE is disabled in the guest, > the same way it was before the kernel/KVM knew about SVE at all. Yup, I agree with you and I'll try writing a patch for this. Thanks, drew _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
