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

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Date:   Wed, 15 Feb 2017 09:57:11 -0700
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Manish Jaggi <mjaggi@...iumnetworks.com>
Cc:     bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        Tirumalesh Chalamarla <tchalamarla@...ium.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Revert: "PCI: Add ACS quirk for all Cavium devices"

On Wed, 15 Feb 2017 22:12:54 +0530
Manish Jaggi <mjaggi@...iumnetworks.com> wrote:

> 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@...hat.com> 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@...hat.com>
> >> Cc: Manish Jaggi <mjaggi@...iumnetworks.com>
> >> Cc: Tirumalesh Chalamarla <tchalamarla@...ium.com>
> >> ---
> >>
> >> 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.

Perfect, thank you Manish.

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 }
> >>   };
> >>   
> >>  
>