linux-kernel - Re: [bug report] GICv4.1: vSGI remains pending across the guest reset

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Message-ID: <ZX8w1vfQzeXP5klL@linux.dev>
Date: Sun, 17 Dec 2023 17:33:10 +0000
From: Oliver Upton <oliver.upton@...ux.dev>
To: Marc Zyngier <maz@...nel.org>
Cc: Kunkun Jiang <jiangkunkun@...wei.com>,
	James Morse <james.morse@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Jean-Philippe Brucker <jean-philippe@...aro.org>,
	"moderated list:ARM SMMU DRIVERS" <linux-arm-kernel@...ts.infradead.org>,
	kvmarm@...ts.linux.dev, open list <linux-kernel@...r.kernel.org>,
	"wanghaibin.wang@...wei.com" <wanghaibin.wang@...wei.com>
Subject: Re: [bug report] GICv4.1: vSGI remains pending across the guest reset

On Sun, Dec 17, 2023 at 11:26:15AM +0000, Marc Zyngier wrote:

[...]

> But this has *nothing* to do with the guest. This is the *host*
> userspace performing a write to the redistributor view, which has
> different semantics. Which is why your earlier description made no
> sense to me.
> 
> I think the problem is slightly larger than what you describe. A write
> to ISPENDR0 should be propagated to the ITS for any values of the
> latch, just like this happens on enabling HW-backed SGIs.
> 
> Can you please give this a go?

What do you think about using this as an opportunity for a bit of
cleanup? It'd be nice unify the various MMIO and uaccess handlers for
SPENDING + CPENDING while being careful about the arch_timer interrupt.

	clear = ~val;
	vgic_uaccess_write_spending(val);
	vgic_uaccess_write_cpending(clear);

Happy to take your fix too, especially in case I missed something
obvious :)

[*] https://git.kernel.org/pub/scm/linux/kernel/git/oupton/linux.git/log/?h=kvm-arm64/vsgi-spending-fixes

-- 
Thanks,
Oliver