linux-kernel - Re: [PATCH v3 07/14] iommufd/viommu: Add iommufd_viommu_get_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: <Z2OpylDlhLXoo3dt@Asurada-Nvidia>
Date: Wed, 18 Dec 2024 21:06:18 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: Baolu Lu <baolu.lu@...ux.intel.com>
CC: <jgg@...dia.com>, <kevin.tian@...el.com>, <will@...nel.org>,
	<corbet@....net>, <joro@...tes.org>, <suravee.suthikulpanit@....com>,
	<robin.murphy@....com>, <dwmw2@...radead.org>, <shuah@...nel.org>,
	<linux-kernel@...r.kernel.org>, <iommu@...ts.linux.dev>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kselftest@...r.kernel.org>,
	<linux-doc@...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>,
	<ddutile@...hat.com>, <yi.l.liu@...el.com>, <patches@...ts.linux.dev>
Subject: Re: [PATCH v3 07/14] iommufd/viommu: Add iommufd_viommu_get_vdev_id
 helper

On Thu, Dec 19, 2024 at 10:05:53AM +0800, Baolu Lu wrote:
> On 12/18/24 13:00, Nicolin Chen wrote:
> > This is a reverse search v.s. iommufd_viommu_find_dev, as drivers may want
> > to convert a struct device pointer (physical) to its virtual device ID for
> > an event injection to the user space VM.
> > 
> > Again, this avoids exposing more core structures to the drivers, than the
> > iommufd_viommu alone.
> > 
> > Signed-off-by: Nicolin Chen<nicolinc@...dia.com>
> > ---
> >   include/linux/iommufd.h        |  8 ++++++++
> >   drivers/iommu/iommufd/driver.c | 20 ++++++++++++++++++++
> >   2 files changed, 28 insertions(+)
> > 
> > diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
> > index b082676c9e43..ac1f1897d290 100644
> > --- a/include/linux/iommufd.h
> > +++ b/include/linux/iommufd.h
> > @@ -190,6 +190,8 @@ struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
> >   					     enum iommufd_object_type type);
> >   struct device *iommufd_viommu_find_dev(struct iommufd_viommu *viommu,
> >   				       unsigned long vdev_id);
> > +unsigned long iommufd_viommu_get_vdev_id(struct iommufd_viommu *viommu,
> > +					 struct device *dev);
> 
> Hi Nicolin,
> 
> This series overall looks good to me. But I have a question that might
> be irrelevant to this series itself.
> 
> The iommufd provides both IOMMUFD_OBJ_DEVICE and IOMMUFD_OBJ_VDEVICE
> objects. What is the essential difference between these two from
> userspace's perspective?

A quick answer is an IOMMUFD_OBJ_DEVICE being a host physical
device and an IOMMUFD_OBJ_VDEVICE being an IOMMUFD_OBJ_DEVICE
related to IOMMUFD_OBJ_VIOMMU. Two of them can be seen in two
different layers. May refer to this graph:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/userspace-api/iommufd.rst?h=v6.13-rc3#n150

> And, which object ID should the IOMMU device
> driver provide when reporting other events in the future?
>
> Currently, the IOMMUFD uAPI reports IOMMUFD_OBJ_DEVICE in the page
> fault message, and IOMMUFD_OBJ_VDEVICE (if I understand it correctly) in
> the vIRQ message. It will be more future-proof if this could be defined
> clearly.

A vIRQ is actually reported per-vIOMMU in this design. Although
in the this series the SMMU driver seems to report a per-device
vIRQ, it internally converts the vDEVICE to a virtual device ID
and packs the virtual device ID into a per-vIOMMU event:

+/**
+ * struct iommu_virq_arm_smmuv3 - ARM SMMUv3 Virtual IRQ
+ *                                (IOMMU_VIRQ_TYPE_ARM_SMMUV3)
+ * @evt: 256-bit ARM SMMUv3 Event record, little-endian.
+ *       (Refer to "7.3 Event records" in SMMUv3 HW Spec)
+ *
+ * StreamID field reports a virtual device ID. To receive a virtual IRQ for a
+ * device, a vDEVICE must be allocated via IOMMU_VDEVICE_ALLOC.
+ */
+struct iommu_virq_arm_smmuv3 {
+	__aligned_le64 evt[4];
 };

Thanks
Nicolin