linux-kernel - Re: [PATCH v5 3/7] PCI/ATS: Initialize PASID in pci_ats

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Message-ID: <20190815045659.GF253360@google.com>
Date:   Wed, 14 Aug 2019 23:56:59 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     sathyanarayanan.kuppuswamy@...ux.intel.com
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        ashok.raj@...el.com, keith.busch@...el.com
Subject: Re: [PATCH v5 3/7] PCI/ATS: Initialize PASID in pci_ats_init()

On Thu, Aug 01, 2019 at 05:06:00PM -0700, sathyanarayanan.kuppuswamy@...ux.intel.com wrote:
> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> 
> Currently, PASID Capability checks are repeated across all PASID API's.
> Instead, cache the capability check result in pci_pasid_init() and use
> it in other PASID API's. Also, since PASID is a shared resource between
> PF/VF, initialize PASID features with default values in pci_pasid_init().
> 
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>

> + * TODO: Since PASID is a shared resource between PF/VF, don't update
> + * PASID features in the same API as a per device feature.

This comment is slightly misleading (at least, it misled *me* :))
because it hints that PASID might be specific to SR-IOV.  But I don't
think that's true, so if you keep a comment like this, please reword
it along the lines of "for SR-IOV devices, the PF's PASID is shared
between the PF and all VFs" so it leaves open the possibility of
non-SR-IOV devices using PASID as well.

Bjorn