On Nov 17, 2023, at 01:43, Chen, Mike Ximing <mike.ximing.c...@intel.com> wrote: > > External email: Use caution opening links or attachments > > >> -----Original Message----- >> From: Chenbo Xia <chen...@nvidia.com> >> Sent: Tuesday, November 14, 2023 8:54 PM >> To: Sevincer, Abdullah <abdullah.sevin...@intel.com> >> Cc: dev@dpdk.org; jer...@marvell.com; Chen, Mike Ximing >> <mike.ximing.c...@intel.com>; Richardson, Bruce >> <bruce.richard...@intel.com>; NBU-Contact-Thomas Monjalon (EXTERNAL) >> <tho...@monjalon.net>; Marchand, David <david.march...@redhat.com>; >> nipun.gu...@amd.com >> Subject: Re: [PATCH v1] bus/pci: revise support PASID control >> >> On Nov 15, 2023, at 01:39, Sevincer, Abdullah <abdullah.sevin...@intel.com> >> wrote: >>> >>> External email: Use caution opening links or attachments >>> >>> >>>> +I don’t know about the details, so it means for different devices that >>>> support >> PASID, they have different offsets? >>> >>>> +Btw, Is this cap still not exposed to user space in latest kernel? >>> >>> Yes, may be different offsets for different devices. >> >> But why? It’s not standard capability? In my understanding, standard cap >> should >> have the same offset definitions for all devices. > > PASID is a part of extended capabilities. Its offset can be different for > different devices. > >> >>> As of now it is not exposed to user. Bruce's test was on 6.2 generic >>> kernel (6.2.0-36-generic) >> >> Will kernel plan to support that? I can see the related work was done by >> Intel but >> somehow it’s not merged into kernel. Could you give more information on this? >> > Hi Chenbo, > As you may know there has been a lot of changes in iommu/vfio/SVA/pasid/SIOV > support in Linux kernel recently. The PASID used to be disabled, but starting > with > kernel 6.2 it is enabled in vfio-pci driver by default. We did contact the > kernel developers > on this issue. They seem to insist that enabling PASID is needed for whatever > new features > they are developing. This breaks the DLB PF PMD as DLB HW requires the PASID > to be > disable for PF to operate properly (otherwise the HW put DLB in a different > mode). We > will continue to talk to the kernel developers on this issue, but in the > meantime would like > to provide this patch so that DPDK PF PMD can still work with latest kernels. > > In term of exposing the PASID capability to the user space. We are aware of > some patches > Submitted in conjunction to the changes mentioned above, for example, > https://lkml.iu.edu/hypermail/linux/kernel/2309.3/02380.html > But we don’t know when and if it will be accepted into the kernel. Hopefully > the patch will > be accepted so we don’t have to use the hard coded offset. > >> If kernel does not want this to be exposed, it means userspace should not >> access >> this. No? >> > The action (disabling PASID) only applies the targeted device. In the DLB PF > PMD case, > the DPDK has full control of the device via vfio-pci. It does not affect > kernel and any > other device's operation.
Thanks for the long explanation. Hope to see follow-up in DPDK when this capability get exposed to user later :) /Chenbo > > Thanks > Mike >> /Chenbo >
