linux-kernel - Re: [PATCH] iommu/vt-d: Remove unnecessary locking in intel_irq_remapping

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Message-ID: <ZEnt+qyN5EJIzCRf@Asurada-Nvidia>
Date:   Wed, 26 Apr 2023 20:37:30 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
CC:     Jason Gunthorpe <jgg@...dia.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Kevin Tian <kevin.tian@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iommu/vt-d: Remove unnecessary locking in
 intel_irq_remapping_alloc()

On Thu, Apr 27, 2023 at 11:20:40AM +0800, Baolu Lu wrote:

> > Attaching WARNINGs:
> > [   19.680725] ------------[ cut here ]------------
> > [   19.681083] WARNING: CPU: 0 PID: 561 at include/linux/mmap_lock.h:161 track_pfn_remap+0xf5/0x100

> > [   19.684817] Call Trace:
> > [   19.684893]  <TASK>
> > [   19.684967]  remap_pfn_range+0x3e/0xa0
> > [   19.685084]  vfio_pci_mmap_fault+0x8a/0x160 [vfio_pci_core]
 
> I took a quick look. It seems that above warnings are irrelevant to this
> commit. Can you please simply revert this commit and check whether there
> are any changes?

I tried on top of the v6.3-rc5 tag. The warnings were triggered
constantly. And reverting the commit fixes it:
nicolinc@...rada-Nvidia:~/work/mkt/images/nicolinc/src/kernel$ git log --oneline -2
cb3dc9b2417e (HEAD -> v6.3-rc5) Revert "iommu/vt-d: Remove unnecessary locking in intel_irq_remapping_alloc()"
7e364e56293b (tag: v6.3-rc5, jgg/linus) Linux 6.3-rc5

I don't think the commit is the causation yet there seems to be
a strong correlation here...

Thanks
Nic