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From: Boris Brezillon <boris.brezillon@collabora.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Rob Herring <robh+dt@kernel.org>,
	Tomeu Vizoso <tomeu.vizoso@collabora.com>,
	Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>,
	Steven Price <steven.price@arm.com>,
	dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] drm/panfrost: Add PANFROST_BO_NO{READ,WRITE} flags
Date: Fri, 1 Oct 2021 09:06:04 +0200	[thread overview]
Message-ID: <20211001090604.6f56106f@collabora.com> (raw)
In-Reply-To: <20210930214424.0a355392@collabora.com>

Hi Robin,

On Thu, 30 Sep 2021 21:44:24 +0200
Boris Brezillon <boris.brezillon@collabora.com> wrote:

> On Thu, 30 Sep 2021 20:47:23 +0200
> Boris Brezillon <boris.brezillon@collabora.com> wrote:
> 
> > So we can create GPU mappings without R/W permissions. Particularly
> > useful to debug corruptions caused by out-of-bound writes.  
> 
> Oops, I forgot to add the PANFROST_BO_PRIVATE flag suggested by Robin
> here [1]. I'll send a v2.

When you're talking about a PANFROST_BO_GPU_PRIVATE flag (or
PANFROST_BO_NO_CPU_ACCESS), you mean something that can set
ARM_LPAE_PTE_SH_IS instead of the unconditional ARM_LPAE_PTE_SH_OS we
have right now [1], right? In this case, how would you pass this info
to the iommu? Looks like we have an IOMMU_CACHE, but I don't think
it reflects what we're trying to do. IOMMU_PRIV is about privileged
mappings, so definitely not what we want. Should we add a new
IOMMU_NO_{EXTERNAL,HOST,CPU}_ACCESS flag for that?

Regards,

Boris

[1]https://elixir.bootlin.com/linux/v5.15-rc3/source/drivers/iommu/io-pgtable-arm.c#L453

      reply	other threads:[~2021-10-01  7:06 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-30 18:47 [PATCH] drm/panfrost: Add PANFROST_BO_NO{READ,WRITE} flags Boris Brezillon
2021-09-30 19:13 ` Alyssa Rosenzweig
2021-09-30 19:40   ` Boris Brezillon
2021-09-30 22:12     ` Alyssa Rosenzweig
2021-10-01  6:47       ` Boris Brezillon
2021-10-01 11:48         ` Alyssa Rosenzweig
2021-10-01 12:09       ` Steven Price
2021-09-30 19:44 ` Boris Brezillon
2021-10-01  7:06   ` Boris Brezillon [this message]

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