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 16:02:40 +0200	[thread overview]
Message-ID: <bc5d6aa8-e8ca-c896-2f39-af074d55e436@samsung.com> (raw)
In-Reply-To: <ZNJCRhGGxS+63Dnr@nvidia.com>

Hi Jason,

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, because __iommu_probe_device() is then called during the 
iommu 'client device' probe on the probed device. Here is a complete 
call stack:

  unwind_backtrace from show_stack+0x10/0x14
  show_stack from dump_stack_lvl+0x58/0x70
  dump_stack_lvl from __iommu_probe_device+0x3d8/0x4b8
  __iommu_probe_device from iommu_probe_device+0x10/0x40
  iommu_probe_device from of_iommu_configure+0xf8/0x1c8
  of_iommu_configure from of_dma_configure_id+0x188/0x450
  of_dma_configure_id from platform_dma_configure+0x24/0x60
  platform_dma_configure from really_probe+0xac/0x3d4
  really_probe from __driver_probe_device+0xa0/0x1e8
  __driver_probe_device from driver_probe_device+0x30/0xd0
  driver_probe_device from __driver_attach+0x10c/0x190
  __driver_attach from bus_for_each_dev+0x60/0xb4
  bus_for_each_dev from bus_add_driver+0xe0/0x208
  bus_add_driver from driver_register+0x7c/0x118
  driver_register from exynos_drm_init+0xe0/0x14c
  exynos_drm_init from do_one_initcall+0x6c/0x318
  do_one_initcall from kernel_init_freeable+0x1c4/0x214
  kernel_init_freeable from kernel_init+0x18/0x12c
  kernel_init from ret_from_fork+0x14/0x2c

Any ideas?

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

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