linux-kernel - Re: [PATCH v2 10/19] iommufd/viommu: Add vdev

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: <20241007171119.GY1365916@nvidia.com>
Date: Mon, 7 Oct 2024 14:11:19 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: kevin.tian@...el.com, will@...nel.org, joro@...tes.org,
	suravee.suthikulpanit@....com, robin.murphy@....com,
	dwmw2@...radead.org, baolu.lu@...ux.intel.com, shuah@...nel.org,
	linux-kernel@...r.kernel.org, iommu@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux-kselftest@...r.kernel.org, eric.auger@...hat.com,
	jean-philippe@...aro.org, mdf@...nel.org, mshavit@...gle.com,
	shameerali.kolothum.thodi@...wei.com, smostafa@...gle.com,
	yi.l.liu@...el.com
Subject: Re: [PATCH v2 10/19] iommufd/viommu: Add vdev_id helpers for IOMMU
 drivers

On Mon, Oct 07, 2024 at 09:36:18AM -0700, Nicolin Chen wrote:
> On Mon, Oct 07, 2024 at 12:38:37PM -0300, Jason Gunthorpe wrote:
> > On Fri, Oct 04, 2024 at 10:19:43PM -0700, Nicolin Chen wrote:
> > > I tried exposing the struct iommufd_viommu to drivers, and was
> > > able to drop a couple of helpers, except these two:
> > > 
> > > struct device *vdev_to_dev(struct iommufd_vdevice *vdev)
> > > {
> > > 	return vdev ? vdev->idev->dev : NULL;
> > > } // Without it, we need to expose struct iommufd_device.
> > > 
> > > struct iommu_domain *
> > > iommufd_viommu_to_parent_domain(struct iommufd_viommu *viommu)
> > > {
> > > 	if (!viommu || !viommu->hwpt)
> > > 		return NULL;
> > > 	return viommu->hwpt->common.domain;
> > > } // Without it, we need to expose struct iommufd_hwpt_page.
> > 
> > It seems OK, there isn't really locking entanglements or performance
> > path on this stuff?
> 
> -----
> The typical use case of the first one is like:
> 	dev = vdev_to_dev(xa_load(&viommu->vdevs, (unsigned long)vdev_id));
> so I am asking for:
> /* Caller should lock via viommu->vdevs_rwsem with proper permission */

Why would vdev_to_dev need that locking? The viommu cannot change hwpt
during its lifecycle?

Jason