Re: [PATCH v2 00/10] Refine the locking for dev->iommu_group

From: Marek Szyprowski <m.szyprowski@samsung.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Chen-Yu Tsai <wenst@chromium.org>, Joerg Roedel <joro@8bytes.org>,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	David Woodhouse <dwmw2@infradead.org>,
	Heiko Stuebner <heiko@sntech.de>,
	iommu@lists.linux.dev, Jernej Skrabec <jernej.skrabec@gmail.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org, linux-sunxi@lists.linux.dev,
	Orson Zhai <orsonzhai@gmail.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Samuel Holland <samuel@sholland.org>,
	Chen-Yu Tsai <wens@csie.org>, Will Deacon <will@kernel.org>,
	Chunyan Zhang <zhang.lyra@gmail.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	Lu Baolu <baolu.lu@linux.intel.com>
Subject: Re: [PATCH v2 00/10] Refine the locking for dev->iommu_group
Date: Tue, 8 Aug 2023 16:51:57 +0200	[thread overview]
Message-ID: <9a31fc21-b5d2-8f2f-0274-9ed43fcfcfbe@samsung.com> (raw)
In-Reply-To: <ZNJRf4Xp8rY1+iT4@nvidia.com>

Hi Jason,

On 08.08.2023 16:30, Jason Gunthorpe wrote:
> On Tue, Aug 08, 2023 at 04:02:40PM +0200, Marek Szyprowski wrote:
>> On 08.08.2023 15:25, Jason Gunthorpe wrote:
>>> On Tue, Aug 08, 2023 at 03:08:30PM +0200, Marek Szyprowski wrote:
>>>>> Any of the drivers that use platform device as the iommu_device will
>>>>> have a problem, please try:
>>>>>
>>>>> https://lore.kernel.org/linux-iommu/ZNIz%2FNVLb6WqqvQx@nvidia.com/
>>>> I've checked and it doesn't help in my case. I will soon check why.
>>> Oh, I botched it. Forgot that the iommu_device->dev is the sysfs
>>> handle not the HW device. Maybe this:
>> This fixed the early lockup, but then system hangs again a bit later. It
>> looks that this device lock in __iommu_probe_device() is really
>> problematic,
> Yes, I expected we'd hit something like this - I checked alot of call
> paths but missed these two. The self-probe is sneaky, but here the
> device_lock is held way up the call chain, I just missed it.
>
> The fix is to just annotate that we already hold the lock when calling
> iommu_probe_device(), since we know in those cases that we must be
> holding it:

Great, this fixed the issue. Feel free to add:

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

 > ...

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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