Re: [PATCH v1] event/dlb2: add support for disabling PASID

[Jerin Jacob <jerinjacobk@gmail.com>]

On Thu, Jun 8, 2023 at 12:59 PM David Marchand
<david.marchand@redhat.com> wrote:
>
> On Thu, Jun 8, 2023 at 7:38 AM Jerin Jacob <jerinjacobk@gmail.com> wrote:
> >
> > On Thu, Jun 8, 2023 at 2:31 AM Abdullah Sevincer
> > <abdullah.sevincer@intel.com> wrote:
> > >
> > > vfio-pci driver in Linux kernel 6.2 enables PASID by default.
> > > In DLB hardware, enabling PASID puts DLB in SIOV mode. This
> > > breaks DLB PF-PMD mode. For DLB PF-PMD mode to function properly
> > > PASID needs to be disabled for kernel 6.2.
> > >
> > > In this commit this issue is addressed and PASID is disabled
> > > by writing a zero to PASID control register.
> > >
> > > Signed-off-by: Abdullah Sevincer <abdullah.sevincer@intel.com>
> >
> > > +       /* The current Linux kernel vfio driver does not expose PASID capability to
> > > +        * users. It also enables PASID by default, which breaks DLB PF PMD. We have
> > > +        * to use the hardcoded offset for now to disable PASID.
> > > +        */
> > > +       pasid_cap_offset = DLB2_PCI_PASID_CAP_OFFSET;
> > > +
> > > +       off = pasid_cap_offset + DLB2_PCI_PASID_CTRL;
> >
> > +++ additional folks.
> >
> > Is make sense to move this helper function to PCI common for disabling
> > PASID for a PCI device so that other driver can use if needed
> > as the implementation is not specific to DLB2.
>
> Yes, having a helper sounds like a first step (and we probably have
> more helpers to add seeing how drivers tend to redefine non vendor
> specific pci configs, but that's another story).

@Abdullah Sevincer  Please move the implementation to code PCI code.

>
> Now, about PASID being enabled by default with Linux 6.2, is this
> breaking of dlb PF something special? Or can we expect many (all?)
> other devices to break too?
> If so, maybe we should disable it in the pci common code.

@Abdullah Sevincer Is implicitly enabling SIOV based on PASID
configuration DLB2 behavior or general PCI behavior that may affect
other NIC's?

>
>
> --
> David Marchand
>