Re: [PATCH] Revert: "PCI: Add ACS quirk for all Cavium devices"

[Manish Jaggi]

Hi Alex,

On 2/15/2017 10:04 PM, Alex Williamson wrote:
> On Tue, 14 Feb 2017 09:18:18 -0700
> Alex Williamson <alex.williamson@xxxxxxxxxx> wrote:
>
> > This reverts commit b404bcfbf035413dcce539c8ba2c9986d220d8ed.
> >
> > The reverted commit makes no attempt to selectively consider devices,
> > current or future.  Instead, it whitelists the entire PCI vendor ID.
> > This is a reckless approach as we clearly cannot know whether future
> > device IDs within this vendor ID are susceptible to peer-to-peer.
> > Additionally, the comment suggests this quirk is only relevant to
> > ThunderX, which raises further doubt whether it is appropriate to
> > apply to the entire vendor ID.
> >
> > Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> > Cc: Manish Jaggi <mjaggi@xxxxxxxxxxxxxxxxxx>
> > Cc: Tirumalesh Chalamarla <tchalamarla@xxxxxxxxxx>
> > ---
> >
> > Please submit a new quirk targeting specific devices
> Sorry, I saw the date on the original commit as January 30, 2016 and
> forgot we're now in 2017, so I figured that this had only recently gone
> in.  Since it's actually been around since 4.6, I'll take a different
> approach.  Instead of reverting, I'm going to assume that this applies
> to ThunderX devices as per the comment.  I'll follow-up with a new
> patch that only applies this to device IDs matching ThunderX as found
> here http://pci-ids.ucw.cz/read/PC/177d  Perhaps in the meantime,
> someone from Cavium will comment on which subset of those devices this
> is actually relevant to.
I will provide another patch with the specific device Ids.
>    Thanks,
>
> Alex
>
> >   drivers/pci/quirks.c |   15 ---------------
> >   1 file changed, 15 deletions(-)
> >
> > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> > index 1800befa8b8b..449eabb438e2 100644
> > --- a/drivers/pci/quirks.c
> > +++ b/drivers/pci/quirks.c
> > @@ -4060,19 +4060,6 @@ static int pci_quirk_amd_sb_acs(struct pci_dev *dev, u16 acs_flags)
> >   #endif
> >   }
> >   
> > -static int pci_quirk_cavium_acs(struct pci_dev *dev, u16 acs_flags)
> > -{
> > -	/*
> > -	 * Cavium devices matching this quirk do not perform peer-to-peer
> > -	 * with other functions, allowing masking out these bits as if they
> > -	 * were unimplemented in the ACS capability.
> > -	 */
> > -	acs_flags &= ~(PCI_ACS_SV | PCI_ACS_TB | PCI_ACS_RR |
> > -		       PCI_ACS_CR | PCI_ACS_UF | PCI_ACS_DT);
> > -
> > -	return acs_flags ? 0 : 1;
> > -}
> > -
> >   /*
> >    * Many Intel PCH root ports do provide ACS-like features to disable peer
> >    * transactions and validate bus numbers in requests, but do not provide an
> > @@ -4276,8 +4263,6 @@ static int pci_quirk_mf_endpoint_acs(struct pci_dev *dev, u16 acs_flags)
> >   	{ PCI_VENDOR_ID_INTEL, PCI_ANY_ID, pci_quirk_intel_spt_pch_acs },
> >   	{ 0x19a2, 0x710, pci_quirk_mf_endpoint_acs }, /* Emulex BE3-R */
> >   	{ 0x10df, 0x720, pci_quirk_mf_endpoint_acs }, /* Emulex Skyhawk-R */
> > -	/* Cavium ThunderX */
> > -	{ PCI_VENDOR_ID_CAVIUM, PCI_ANY_ID, pci_quirk_cavium_acs },
> >   	{ 0 }
> >   };
> >