linux-kernel - Re: [PATCH] KVM: arm64: vgic: fix GICR_STATUSR in vgic_v3_rd

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Message-ID: <mhwgdkcgoan7r53bubpvlnu4xoexmnldwlk6ni5zjvkn4cnr72@fhxnwlfw536t>
Date: Mon, 30 Sep 2024 14:20:35 +0800
From: Jia Qingtong <jiaqingtong97@...il.com>
To: Marc Zyngier <maz@...nel.org>
Cc: Oliver Upton <oliver.upton@...ux.dev>, 
	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>, Joey Gouly <joey.gouly@....com>, 
	Jia Qingtong <jiaqingtong@...wei.com>, linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: arm64: vgic: fix GICR_STATUSR in
 vgic_v3_rd_registers

On 29 Sep 10:38, Marc Zyngier wrote:
> On Sun, 29 Sep 2024 05:39:35 +0100,
> jiaqingtong97@...il.com wrote:
> > 
> > From: Jia Qingtong <jiaqingtong@...wei.com>
> > 
> > vgic_uaccess use bsearch search regs in vgic_io_device.regions, but the
> > GICR_STATUSR have wrong order in vgic_v3_rd_registers.
> > When check all vgic_register_region, it turned out that only
> > vgic_v3_rd_registers has this problem.
> > 
> > It's harmless since vgic_uaccess behaves as RAZ&WI when it can't find the
> > specified reg. This is exactly the same as the behavior of the GICR_STATUSR
> > register.
> >
> > So just move GICR_STATUSR to the right place.
> 
> That looks correct, but I think we should have some code that ensures
> that these tables are correct at boot time, just like we're doing for
> the system registers. Or completely remove our reliance on bsearch().
> 
struct vgic_register_region was defined in vgic-{its,mmio-v2,mmio-v3},
do you think it's appropriate to extern and check tables's item order in
vgic-init.c's kvm_vgic_hyp_init?.

> Another thing is that GICD_STATUSR looks pretty wrong. It is handled
> as RAO, but we never clear any "error" (it is WI). This has been buggy
> since GICv3 save/restore was added, 7 years ago.
> 
Let's change it to RAZ? We will implement the complete logic when someone
really needs this feature.

> Do you mind spinning a series fixing this up?
> 
Sure. 

> Thanks,
> 
> 	M.
> 
> -- 
> Without deviation from the norm, progress is not possible.

--
Thanks,
Qingtong