Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 09 May 2019 08:58:23 +0100
Message-ID: <867eb09i00.wl-marc.zyngier@arm.com>
From:   Marc Zyngier <marc.zyngier@arm.com>
To:     Heyi Guo <guoheyi@huawei.com>
Cc:     <linux-kernel@vger.kernel.org>,
        Christoffer Dall <christoffer.dall@arm.com>,
        wanghaibin 00208455 <wanghaibin.wang@huawei.com>
Subject: Re: Why do we mark vpending table as non-shareable in GICR_VPENDBASER?
In-Reply-To: <fbee07c9-ec3b-d443-2132-7208dae38539@huawei.com>
References: <fbee07c9-ec3b-d443-2132-7208dae38539@huawei.com>
User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue)
 FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 EasyPG/1.0.0 Emacs/26
 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO)
Organization: ARM Ltd
MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue")
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, 09 May 2019 08:10:09 +0100,
Heyi Guo <guoheyi@huawei.com> wrote:
> 
> Hi Marc,
> 
> We can see in its_vpe_schedule() the shareability bits of
> GICR_VPENDBASER are set as non-shareable, But we set physical
> PENDBASER as inner-shareable. Is there any special reason for doing
> this? If it is because the vpending table is GICR specific, why
> don't we do the same for physical pending table?

That's a good question. They should have similar attributes.

> We have not seen function issue with this setting, but a special
> detector in our hardware warns us that there are non-shareable
> requests sent out while some inner shareable cache entries still
> present in the cache, and it may cause data inconsistent.

The main issue with the inner-shareable attributes and the GIC is that
nothing in the spec says that CPUs and GIC have to be in the same
inner-shareable domain, as the system can have as many as you want.

You obviously have built it with GICR in the same inner-shareability
domain as the CPU. I'm happy to change the VPENDBASER attributes,
given that the CPU has a mapping to that memory already, and that
shouldn't affect systems where GICR isn't in the same inner shareable
domain anyway.

Thanks,

	M.

-- 
Jazz is not dead, it just smell funny.