From: Jason Gunthorpe <jgg@ziepe.ca>
To: Josef Bacik <josef@toxicpanda.com>
Cc: joro@8bytes.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] amd/iommu: do not split domain flushes when flushing the entire range
Date: Thu, 12 Mar 2026 10:40:25 -0300 [thread overview]
Message-ID: <20260312134025.GJ1469476@ziepe.ca> (raw)
In-Reply-To: <ad8652c5e9f8aeee05e2103f4987589cdd4a3fd0.1772659768.git.josef@toxicpanda.com>
On Wed, Mar 04, 2026 at 04:30:03PM -0500, Josef Bacik wrote:
> We are hitting the following soft lockup in production on v6.6 and
> v6.12, but the bug exists in all versions
>
> watchdog: BUG: soft lockup - CPU#24 stuck for 31s! [tokio-runtime-w:1274919]
> CPU: 24 PID: 1274919 Comm: tokio-runtime-w Not tainted 6.6.105+ #1
> Hardware name: Google Google Compute Engine/Google Comput Engine, BIOS Google 10/25/2025
> RIP: 0010:__raw_spin_unlock_irqrestore+0x21/0x30
> Call Trace:
> <TASK>
> amd_iommu_attach_device+0x69/0x450
> __iommu_device_set_domain+0x7b/0x190
> __iommu_group_set_core_domain+0x61/0xd0
> iommu_detatch_group+0x27/0x40
> vfio_iommu_type1_detach_group+0x157/0x780 [vfio_iommu_type1]
> vfio_group_detach_container+0x59/0x160 [vfio]
> vfio_group_fops_release+0x4d/0x90 [vfio]
> __fput+0x95/0x2a0
> task_work_run+0x93/0xc0
> do_exit+0x321/0x950
> do_group_exit+0x7f/0xa0
> get_signal_0x77d/0x780
> </TASK>
>
> This occurs because we're a VM and we're splitting up the size
> CMD_INV_IOMMU_ALL_PAGES_ADDRESS we get from
> amd_iommu_domain_flush_tlb_pde() into a bunch of smaller flushes.
This function doesn't exist in the upstream kernel anymore, and the
new code doesn't generate CMD_INV_IOMMU_ALL_PAGES_ADDRESS flushes at
all, AFAIK.
Your patch makes sense, but it needs to go to stable only somehow.
Jason
next prev parent reply other threads:[~2026-03-12 13:40 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-04 21:30 [PATCH] amd/iommu: do not split domain flushes when flushing the entire range Josef Bacik
2026-03-12 13:40 ` Jason Gunthorpe [this message]
2026-03-14 18:24 ` Josef Bacik
2026-03-26 22:05 ` Jason Gunthorpe
2026-03-24 20:14 ` Josef Bacik
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