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Date: Tue, 13 Oct 2026 02:51:48 -0700
From: Oliver Upton <oupton@kernel.org>
To: Fuad Tabba <fuad.tabba@linux.dev>
Cc: Marc Zyngier <maz@kernel.org>, Joey Gouly <joey.gouly@arm.com>,
	Steffen Eiden <seiden@linux.ibm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Zenghui Yu <yuzenghui@huawei.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Mark Rutland <mark.rutland@arm.com>,
	Andre Przywara <andre.przywara@arm.com>,
	linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
	linux-kernel@vger.kernel.org, Fuad Tabba <tabba@google.com>
Subject: Re: [PATCH v2 0/2] KVM: arm64: vgic-its: Fix LPI double mapping and
 DISCARD
Message-ID: <as3_NKT20MNdqaJR@kernel.org>
References: <20261013081646.933312-1-fuad.tabba@linux.dev>
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In-Reply-To: <20261013081646.933312-1-fuad.tabba@linux.dev>

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