Re: [PATCH v7 1/7] PCI/ATS: Fix pci_prg_resp_pasid_required() dependency issues

[Kuppuswamy Sathyanarayanan]

Hi Bjorn,

Thanks for looking into this patch set.

On 9/5/19 12:18 PM, Bjorn Helgaas wrote:
> On Wed, Aug 28, 2019 at 03:14:01PM -0700, sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx wrote:
> > From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> >
> > Since pci_prg_resp_pasid_required() function has dependency on both
> > PASID and PRI, define it only if both CONFIG_PCI_PRI and
> > CONFIG_PCI_PASID config options are enabled.
> >
> > Fixes: e5567f5f6762 ("PCI/ATS: Add pci_prg_resp_pasid_required()
> > interface.")
> [Don't split tags, including "Fixes:" across lines]
>
> This definitely doesn't fix e5567f5f6762.  That commit added
> pci_prg_resp_pasid_required(), but with no dependency on
> CONFIG_PCI_PRI or CONFIG_PCI_PASID.
>
> This patch is only required when a subsequent patch is applied.  It
> should be squashed into the commit that requires it so it's obvious
> why it's needed.
>
> I've been poking at this series, and I'll post a v8 soon with this and
> other fixes.
In your v8 submission you did not merge this patch. You did not use
pri_cap or pasid_cap cached values. Instead you have re-read the
value from register. Is this intentional?

Since this function will be called for every VF device we might loose 
some performance benefit.

> > Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> > ---
> >   drivers/pci/ats.c       | 10 ++++++----
> >   include/linux/pci-ats.h | 12 +++++++++---
> >   2 files changed, 15 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
> > index e18499243f84..cdd936d10f68 100644
> > --- a/drivers/pci/ats.c
> > +++ b/drivers/pci/ats.c
> > @@ -395,6 +395,8 @@ int pci_pasid_features(struct pci_dev *pdev)
> >   }
> >   EXPORT_SYMBOL_GPL(pci_pasid_features);
> >   
> > +#ifdef CONFIG_PCI_PRI
> > +
> >   /**
> >    * pci_prg_resp_pasid_required - Return PRG Response PASID Required bit
> >    *				 status.
> > @@ -402,10 +404,8 @@ EXPORT_SYMBOL_GPL(pci_pasid_features);
> >    *
> >    * Returns 1 if PASID is required in PRG Response Message, 0 otherwise.
> >    *
> > - * Even though the PRG response PASID status is read from PRI Status
> > - * Register, since this API will mainly be used by PASID users, this
> > - * function is defined within #ifdef CONFIG_PCI_PASID instead of
> > - * CONFIG_PCI_PRI.
> > + * Since this API has dependency on both PRI and PASID, protect it
> > + * with both CONFIG_PCI_PRI and CONFIG_PCI_PASID.
> >    */
> >   int pci_prg_resp_pasid_required(struct pci_dev *pdev)
> >   {
> > @@ -425,6 +425,8 @@ int pci_prg_resp_pasid_required(struct pci_dev *pdev)
> >   }
> >   EXPORT_SYMBOL_GPL(pci_prg_resp_pasid_required);
> >   
> > +#endif
> > +
> >   #define PASID_NUMBER_SHIFT	8
> >   #define PASID_NUMBER_MASK	(0x1f << PASID_NUMBER_SHIFT)
> >   /**
> > diff --git a/include/linux/pci-ats.h b/include/linux/pci-ats.h
> > index 1ebb88e7c184..1a0bdaee2f32 100644
> > --- a/include/linux/pci-ats.h
> > +++ b/include/linux/pci-ats.h
> > @@ -40,7 +40,6 @@ void pci_disable_pasid(struct pci_dev *pdev);
> >   void pci_restore_pasid_state(struct pci_dev *pdev);
> >   int pci_pasid_features(struct pci_dev *pdev);
> >   int pci_max_pasids(struct pci_dev *pdev);
> > -int pci_prg_resp_pasid_required(struct pci_dev *pdev);
> >   
> >   #else  /* CONFIG_PCI_PASID */
> >   
> > @@ -67,11 +66,18 @@ static inline int pci_max_pasids(struct pci_dev *pdev)
> >   	return -EINVAL;
> >   }
> >   
> > +#endif /* CONFIG_PCI_PASID */
> > +
> > +#if defined(CONFIG_PCI_PRI) && defined(CONFIG_PCI_PASID)
> > +
> > +int pci_prg_resp_pasid_required(struct pci_dev *pdev);
> > +
> > +#else /* CONFIG_PCI_PASID && CONFIG_PCI_PRI */
> > +
> >   static inline int pci_prg_resp_pasid_required(struct pci_dev *pdev)
> >   {
> >   	return 0;
> >   }
> > -#endif /* CONFIG_PCI_PASID */
> > -
> > +#endif
> >   
> >   #endif /* LINUX_PCI_ATS_H*/
> > --
> > 2.21.0
--
Sathyanarayanan Kuppuswamy
Linux kernel developer