Re: [PATCH v2 0/2] KVM: arm64: vgic-its: Fix LPI double mapping and DISCARD

[Oliver Upton <oupton@kernel.org>]

On Tue, Oct 13, 2026 at 09:16:44AM +0100, Fuad Tabba wrote:
> Hi folks,
> 
> Changes since v1 [1]:
>   - Dropped the second mapping of an LPI at MAPTI, instead of keeping a
>     doubly mapped LPI out of GICv4 forwarding. (Marc)
>   - Keyed that check on whether an ITE maps the LPI, not on whether its
>     vgic_irq exists.
>   - Added a patch that makes DISCARD remove the pending state. (Marc)
> 
> Two fixes to the ITS emulation. The first stops a guest from mapping
> one LPI from two events, which can oops a GICv4 host when the VMM then
> routes an assigned device's MSI to the second event. The second makes
> DISCARD remove the LPI's pending state, as the spec requires.
> 
> Tested on QEMU, which emulates a GICv4 ITS. A local reproducer with two
> vCPUs DISCARDs an LPI that's pending in the other vCPU's list register.
> On rc3, and with patch 2 but without its halt, the guest still takes
> the LPI. With the series applied, it doesn't.
> 
> Based on Linux 7.3-rc3 (fd73f4a665989).
> 
> Cheers,
> /fuad
> 
> [1] https://lore.kernel.org/all/20261012084743.2228612-1-fuad.tabba@linux.dev/
> 
> Fuad Tabba (2):
>   KVM: arm64: vgic-its: Don't map an LPI from more than one event
>   KVM: arm64: vgic-its: Remove the pending state of a discarded LPI

Looks good. As all of these VGIC fixes depend on reliably synchronizing
hwstate I'll assume Marc will apply this patchset after his own series.

Reviewed-by: Oliver Upton <oupton@kernel.org>

Thanks,
Oliver