linux-kernel - Re: [PATCH v4 11/23] iommufd/viommu: Add IOMMUFD_CMD_HW_QUEUE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aCZPcH+GiZKUjzWn@Asurada-Nvidia>
Date: Thu, 15 May 2025 13:32:48 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: Jason Gunthorpe <jgg@...dia.com>
CC: <kevin.tian@...el.com>, <corbet@....net>, <will@...nel.org>,
	<bagasdotme@...il.com>, <robin.murphy@....com>, <joro@...tes.org>,
	<thierry.reding@...il.com>, <vdumpa@...dia.com>, <jonathanh@...dia.com>,
	<shuah@...nel.org>, <jsnitsel@...hat.com>, <nathan@...nel.org>,
	<peterz@...radead.org>, <yi.l.liu@...el.com>, <mshavit@...gle.com>,
	<praan@...gle.com>, <zhangzekun11@...wei.com>, <iommu@...ts.linux.dev>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-tegra@...r.kernel.org>,
	<linux-kselftest@...r.kernel.org>, <patches@...ts.linux.dev>,
	<mochs@...dia.com>, <alok.a.tiwari@...cle.com>, <vasant.hegde@....com>
Subject: Re: [PATCH v4 11/23] iommufd/viommu: Add IOMMUFD_CMD_HW_QUEUE_ALLOC
 ioctl

On Thu, May 15, 2025 at 03:59:38PM -0300, Jason Gunthorpe wrote:
> On Thu, May 15, 2025 at 11:16:45AM -0700, Nicolin Chen wrote:
> > > I don't think this actually works like this without an unmap
> > > callback. unmap will break:
> > > 
> > > 			iommufd_access_notify_unmap(iopt, area_first, length);
> > > 			/* Something is not responding to unmap requests. */
> > > 			tries++;
> > > 			if (WARN_ON(tries > 100))
> > > 				return -EDEADLOCK;
> > > 
> > > If it can't shoot down the pinning.
> > 
> > Hmm, I thought we want the unmap to fail until VMM releases the HW
> > QUEUE first? In what case, does VMM wants to unmap while holding
> > the queue pages?
> 
> Well, if that is what we want to do then this needs to be revised
> somehow..

Yea, unless we have a strong reason to allow unmap while holding
the HW queue.

I think we could set a new flag:

 enum {
 	IOMMUFD_ACCESS_RW_READ = 0,
 	IOMMUFD_ACCESS_RW_WRITE = 1 << 0,
 	/* Set if the caller is in a kthread then rw will use kthread_use_mm() */
 	IOMMUFD_ACCESS_RW_KTHREAD = 1 << 1,
+	IOMMUFD_ACCESS_NO_UNMAP = 1 << 3,
 
 	/* Only for use by selftest */
 	__IOMMUFD_ACCESS_RW_SLOW_PATH = 1 << 2,
 };

and reject iopt_unmap_iova_range().

Thanks
Nicolin