> -----Original Message-----
> From: Baolu Lu <baolu...@linux.intel.com>
> Sent: Thursday, March 13, 2025 7:53 PM
> To: Borah, Chaitanya Kumar <chaitanya.kumar.bo...@intel.com>
> Cc: baolu...@linux.intel.com; intel-gfx@lists.freedesktop.org; intel-
> x...@lists.freedesktop.org; io...@lists.linux.dev
> Subject: Re: Regression on drm-tip
>
> On 2025/3/13 16:51, Borah, Chaitanya Kumar wrote:
> > Hello Lu,
> >
> > Hope you are doing well. I am Chaitanya from the linux graphics team in
> Intel.
> >
> > This mail is regarding a regression we are seeing in our CI runs[1] on
> > drm-tip
> repository.
> >
> > ``````````````````````````````````````````````````````````````````````
> > ``````````` <4>[ 2.856622] WARNING: possible circular locking
> > dependency detected <4>[ 2.856631]
> > 6.14.0-rc5-CI_DRM_16217-gc55ef90b69d3+ #1 Tainted: G I <4>[
> > 2.856642] ------------------------------------------------------
> > <4>[ 2.856650] swapper/0/1 is trying to acquire lock:
> > <4>[ 2.856657] ffffffff8360ecc8
> > (iommu_probe_device_lock){+.+.}-{3:3}, at:
> > iommu_probe_device+0x1d/0x70 <4>[ 2.856679]
> > but task is already holding lock:
> > <4>[ 2.856686] ffff888102ab6fa8
> > (&device->physical_node_lock){+.+.}-{3:3}, at:
> > intel_iommu_init+0xea1/0x1220
> > ``````````````````````````````````````````````````````````````````````
> > ```````````
> > Details log can be found in [2].
> >
> > After bisecting the tree, the following patch [3] seems to be the
> > first "bad" commit
> >
> > ``````````````````````````````````````````````````````````````````````
> > ```````````````````````````````````
> > commit b150654f74bf0df8e6a7936d5ec51400d9ec06d8
> > Author: Lu Baolumailto:baolu...@linux.intel.com
> > Date: Fri Feb 28 18:27:26 2025 +0800
> >
> > iommu/vt-d: Fix suspicious RCU usage
> >
> > ``````````````````````````````````````````````````````````````````````
> > ```````````````````````````````````
> >
> > We also verified that if we revert the patch the issue is not seen.
> >
> > Could you please check why the patch causes this regression and provide a
> fix if necessary?
>
> Can you please take a quick test to check if the following fix works?
>
> diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c index
> e540092d664d..06debeaec643 100644
> --- a/drivers/iommu/intel/dmar.c
> +++ b/drivers/iommu/intel/dmar.c
> @@ -2051,8 +2051,13 @@ int enable_drhd_fault_handling(unsigned int cpu)
> if (iommu->irq || iommu->node != cpu_to_node(cpu))
> continue;
>
> + /*
> + * Call dmar_alloc_hwirq() with dmar_global_lock held,
> + * could cause possible lock race condition.
> + */
> + up_read(&dmar_global_lock);
> ret = dmar_set_interrupt(iommu);
> -
> + down_read(&dmar_global_lock);
> if (ret) {
> pr_err("DRHD %Lx: failed to enable fault, interrupt,
> ret %d\n",
> (unsigned long long)drhd->reg_base_addr, ret);
>
> Thanks,
> baolu
We still see the issue with this change.
Regards
Chaitanya
