[PATCH v3 0/5] KVM: arm64: Add LR overflow infrastructure (the dregs, the bad and the ugly)

[Fuad Tabba]

Hi Marc,

On Mon, 17 Nov 2025 at 09:15, Marc Zyngier <maz at kernel.org> wrote:
>
> This is a follow-up to the original series [1] (and fixes [2][3])
> with a bunch of bug-fixes and improvements. At least one patch has
> already been posted, but I thought I might repost it as part of a
> series, since I accumulated more stuff:

I'd like to test this series as well. Do you have it applied in one of
your branches at
https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git
, or which commit is it based on?

Thanks,
/fuad

> - The first patch addresses Mark's observation that the no-vgic-v3
>   test has been broken once more. At some point, we'll have to retire
>   that functionality, because even if we keep fixing the SR handling,
>   nobody tests the actual interrupt state exposure to userspace, which
>   I'm pretty sure has badly been broken for at least 5 years.
>
> - The second one addresses a report from Fuad that on QEMU,
>   ICH_HCR_EL2.TDIR traps ICC_DIR_EL1 on top of ICV_DIR_EL1, leading to
>   the host exploding on deactivating an interrupt. This behaviour is
>   allowed by the spec, so make sure we clear all trap bits
>
> - Running vgic_irq in an L1 guest (the test being an L2) results in a
>   MI storm on the host, as the state synchronisation is done at the
>   wrong place, much like it was on the non-NV path before it was
>   reworked. Apply the same methods to the NV code, and enjoy much
>   better MI emulation, now tested all the way into an L3.
>
> - Nuke a small leftover from previous rework.
>
> - Force a read-back of ICH_MISR_EL2 when disabling the vgic, so that
>   the trap prevents too many spurious MIs in an L1 guest, as the write
>   to ICH_HCR_EL2 does exactly nothing on its own when running under
>   FEAT_NV2.
>
> Oliver: this is starting to be a large series of fixes on top of the
> existing series, plus the two patches you have already added. I'd be
> happy to respin a full v4 with the fixes squashed into their original
> patches. On the other hand, if you want to see the history in its full
> glory, that also works for me.
>
> [1] https://msgid.link/20251109171619.1507205-1-maz@kernel.org
> [2] https://msgid.link/20251113172524.2795158-1-maz@kernel.org
> [3] https://lore.kernel.org/kvmarm/86frahu21h.wl-maz@kernel.org
>
> Marc Zyngier (5):
>   KVM: arm64: GICv3: Don't advertise ICH_HCR_EL2.En==1 when no vgic is
>     configured
>   KVM: arm64: GICv3: Completely disable trapping on vcpu exit
>   KVM: arm64: GICv3: nv: Resync LRs/VMCR/HCR early for better MI
>     emulation
>   KVM: arm64: GICv3: Remove vgic_hcr workaround handling leftovers
>   KVM: arm64: GICv3: Force exit to sync ICH_HCR_EL2.En
>
>  arch/arm64/include/asm/kvm_hyp.h     |  1 +
>  arch/arm64/kvm/hyp/vgic-v3-sr.c      | 11 +++-
>  arch/arm64/kvm/vgic/vgic-v3-nested.c | 78 ++++++++++++++++------------
>  arch/arm64/kvm/vgic/vgic-v3.c        |  3 ++
>  arch/arm64/kvm/vgic/vgic.c           |  6 ++-
>  arch/arm64/kvm/vgic/vgic.h           |  1 +
>  6 files changed, 62 insertions(+), 38 deletions(-)
>
> --
> 2.47.3
>
>