On Fri, 06 Oct 2023 12:13:00 +0100, Marc Zyngier <maz@xxxxxxxxxx> wrote: > > On Fri, 06 Oct 2023 10:35:57 +0100, > Oliver Upton <oliver.upton@xxxxxxxxx> wrote: > > > > Unlike nVHE, there is no need to switch the stage-2 MMU around on guest > > entry/exit in VHE mode as the host is running at EL2. Despite this KVM > > reloads the stage-2 on every guest entry, which is needless. > > > > This series moves the setup of the stage-2 MMU context to vcpu_load() > > when running in VHE mode. This is likely to be a win across the board, > > but also allows us to remove an ISB on the guest entry path for systems > > with one of the speculative AT errata. > > > > None of my machines affected by the AT errata are VHE-capable, so it'd > > be appreciated if someone could give this series a go and make sure I > > haven't wrecked anything. > > It totally breaks on my A55 board. Running a single guest seems OK, > but running a number of the concurrently makes them explode early on > (faults in EFI...) > > I guess we end-up running with the wrong VTTBR at times, which would > be interesting... Fun fact: diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c index b0cafd7c5f8f..40c84db5884a 100644 --- a/arch/arm64/kvm/hyp/vhe/switch.c +++ b/arch/arm64/kvm/hyp/vhe/switch.c @@ -195,6 +195,11 @@ static int __kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu) sysreg_restore_guest_state_vhe(guest_ctxt); __debug_switch_to_guest(vcpu); + WARN_ONCE(kvm_get_vttbr(vcpu->arch.hw_mmu) != read_sysreg(vttbr_el2), + "Oh crap %llx vs %llx\n", + kvm_get_vttbr(vcpu->arch.hw_mmu), + read_sysreg(vttbr_el2)); + if (is_hyp_ctxt(vcpu)) vcpu_set_flag(vcpu, VCPU_HYP_CONTEXT); else [ 36.190355] Oh crap 10000057a6001 vs 57a6001 My bet is that the VMID isn't allocated on first load, and everything goes downhill from there. M. -- Without deviation from the norm, progress is not possible.
