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From: Jason Gunthorpe <jgg@nvidia.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: joro@8bytes.org, will@kernel.org, iommu@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org, m.szyprowski@samsung.com,
	heiko@sntech.de, jernej.skrabec@gmail.com,
	thierry.reding@gmail.com, vdumpa@nvidia.com
Subject: Re: [PATCH 8/8] iommu: Improve map/unmap sanity checks
Date: Fri, 22 Sep 2023 14:28:31 -0300	[thread overview]
Message-ID: <20230922172831.GA145934@nvidia.com> (raw)
In-Reply-To: <fef0b304-5a19-b2a3-c399-7f21c05623bf@arm.com>

On Tue, Sep 19, 2023 at 01:18:31PM +0100, Robin Murphy wrote:

> > This is not a theoretical question - does any in-kernel code actually
> > do that and expect it to work? I didn't notice any..
> 
> I was hoping to have to say I'd only seen it in unmerged (e.g. [1]) and
> downstream code, but then I found drivers/net/ipa/ :(

Aiiie, what is that doing? Mapping something into the dma-api owned
domain!?!

See this is why I think stronger invarients are a good idea, we can't
police the entire kernel but we can make the entry points explode if
someone is doing something WRONG.

> All that said, I don't mind if you want to propose a separate patch to turn
> certain external caller conditions into noisy warnings, but I wouldn't want
> to tie it up with any other changes which would risk getting caught in the
> crossfire if someone does then hit a newly-introduced warning and start
> arguing to revert it. And I'm not going to do so in any of my patches since
> as above I don't personally believe it's a valuable thing to do.

Ok, that make sense

Jason

WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgg@nvidia.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: joro@8bytes.org, will@kernel.org, iommu@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org, m.szyprowski@samsung.com,
	heiko@sntech.de, jernej.skrabec@gmail.com,
	thierry.reding@gmail.com, vdumpa@nvidia.com
Subject: Re: [PATCH 8/8] iommu: Improve map/unmap sanity checks
Date: Fri, 22 Sep 2023 14:28:31 -0300	[thread overview]
Message-ID: <20230922172831.GA145934@nvidia.com> (raw)
In-Reply-To: <fef0b304-5a19-b2a3-c399-7f21c05623bf@arm.com>

On Tue, Sep 19, 2023 at 01:18:31PM +0100, Robin Murphy wrote:

> > This is not a theoretical question - does any in-kernel code actually
> > do that and expect it to work? I didn't notice any..
> 
> I was hoping to have to say I'd only seen it in unmerged (e.g. [1]) and
> downstream code, but then I found drivers/net/ipa/ :(

Aiiie, what is that doing? Mapping something into the dma-api owned
domain!?!

See this is why I think stronger invarients are a good idea, we can't
police the entire kernel but we can make the entry points explode if
someone is doing something WRONG.

> All that said, I don't mind if you want to propose a separate patch to turn
> certain external caller conditions into noisy warnings, but I wouldn't want
> to tie it up with any other changes which would risk getting caught in the
> crossfire if someone does then hit a newly-introduced warning and start
> arguing to revert it. And I'm not going to do so in any of my patches since
> as above I don't personally believe it's a valuable thing to do.

Ok, that make sense

Jason

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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2023-09-22 17:28 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-12 16:18 [PATCH 0/8] iommu: Clean up map/unmap ops Robin Murphy
2023-09-12 16:18 ` Robin Murphy
2023-09-12 16:18 ` [PATCH 1/8] iommu/exynos: Update to {map,unmap}_pages Robin Murphy
2023-09-12 16:18   ` Robin Murphy
2023-09-12 16:18 ` [PATCH 2/8] iommu/omap: " Robin Murphy
2023-09-12 16:18   ` Robin Murphy
2023-09-12 16:18 ` [PATCH 3/8] iommu/rockchip: " Robin Murphy
2023-09-12 16:18   ` Robin Murphy
2023-09-12 16:18 ` [PATCH 4/8] iommu/sun50i: " Robin Murphy
2023-09-12 16:18   ` Robin Murphy
2023-09-12 16:18 ` [PATCH 5/8] iommu/tegra-gart: " Robin Murphy
2023-09-12 16:18   ` Robin Murphy
2023-09-12 16:18 ` [PATCH 6/8] iommu/tegra-smmu: " Robin Murphy
2023-09-12 16:18   ` Robin Murphy
2023-09-12 16:18 ` [PATCH 7/8] iommu: Retire map/unmap ops Robin Murphy
2023-09-12 16:18   ` Robin Murphy
2023-09-13 14:40   ` Jason Gunthorpe
2023-09-13 14:40     ` Jason Gunthorpe
2023-09-12 16:18 ` [PATCH 8/8] iommu: Improve map/unmap sanity checks Robin Murphy
2023-09-12 16:18   ` Robin Murphy
2023-09-13 14:39   ` Jason Gunthorpe
2023-09-13 14:39     ` Jason Gunthorpe
2023-09-13 18:46     ` Robin Murphy
2023-09-13 18:46       ` Robin Murphy
2023-09-14 12:48       ` Jason Gunthorpe
2023-09-14 12:48         ` Jason Gunthorpe
2023-09-14 14:23         ` Robin Murphy
2023-09-14 14:23           ` Robin Murphy
2023-09-14 16:48           ` Jason Gunthorpe
2023-09-14 16:48             ` Jason Gunthorpe
2023-09-19 12:18             ` Robin Murphy
2023-09-19 12:18               ` Robin Murphy
2023-09-22 17:28               ` Jason Gunthorpe [this message]
2023-09-22 17:28                 ` Jason Gunthorpe
2023-09-25 10:05 ` [PATCH 0/8] iommu: Clean up map/unmap ops Joerg Roedel
2023-09-25 10:05   ` Joerg Roedel
2023-09-25 15:33   ` Jernej Škrabec
2023-09-25 15:33     ` Jernej Škrabec
2023-09-26  9:23     ` Joerg Roedel
2023-09-26  9:23       ` Joerg Roedel
2023-09-26 12:01       ` Robin Murphy
2023-09-26 12:01         ` Robin Murphy
2023-09-26 14:57         ` Joerg Roedel
2023-09-26 14:57           ` Joerg Roedel

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