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Date: Sun, 17 Dec 2023 17:34:38 +0000
From: Oliver Upton <oliver.upton@linux.dev>
To: Marc Zyngier <maz@kernel.org>
Cc: Kunkun Jiang <jiangkunkun@huawei.com>,
	James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Zenghui Yu <yuzenghui@huawei.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	"moderated list:ARM SMMU DRIVERS" <linux-arm-kernel@lists.infradead.org>,
	kvmarm@lists.linux.dev, open list <linux-kernel@vger.kernel.org>,
	"wanghaibin.wang@huawei.com" <wanghaibin.wang@huawei.com>
Subject: Re: [bug report] GICv4.1: vSGI remains pending across the guest reset
Message-ID: <ZX8xLhFFqTXRFQtd@linux.dev>
References: <7e7f2c0c-448b-10a9-8929-4b8f4f6e2a32@huawei.com>
 <87a5q983zc.wl-maz@kernel.org>
 <ZX8w1vfQzeXP5klL@linux.dev>
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In-Reply-To: <ZX8w1vfQzeXP5klL@linux.dev>

On Sun, Dec 17, 2023 at 05:33:16PM +0000, Oliver Upton wrote:
> 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.

Cut myself off... Meant to say that user writes to SPENDING for GICv3
can then be treated as:

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

-- 
Thanks,
Oliver