linux-kernel - Re: [PATCH v2 1/7] PCI: Keep the ACS capability offset in device

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Date:   Mon, 6 Jul 2020 18:18:44 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Rajat Jain <rajatja@...gle.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        "open list:AMD IOMMU (AMD-VI)" <iommu@...ts.linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Raj Ashok <ashok.raj@...el.com>,
        "Krishnakumar, Lalithambika" <lalithambika.krishnakumar@...el.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Prashant Malani <pmalani@...gle.com>,
        Benson Leung <bleung@...gle.com>,
        Todd Broch <tbroch@...gle.com>,
        Alex Levin <levinale@...gle.com>,
        Mattias Nissler <mnissler@...gle.com>,
        Rajat Jain <rajatxjain@...il.com>,
        Bernie Keany <bernie.keany@...el.com>,
        Aaron Durbin <adurbin@...gle.com>,
        Diego Rivas <diegorivas@...gle.com>,
        Duncan Laurie <dlaurie@...gle.com>,
        Furquan Shaikh <furquan@...gle.com>,
        Jesse Barnes <jsbarnes@...gle.com>,
        Christian Kellner <christian@...lner.me>,
        Alex Williamson <alex.williamson@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Oliver O'Halloran <oohall@...il.com>,
        Saravana Kannan <saravanak@...gle.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Subject: Re: [PATCH v2 1/7] PCI: Keep the ACS capability offset in device

On Mon, Jul 06, 2020 at 03:16:42PM -0700, Rajat Jain wrote:
> On Mon, Jul 6, 2020 at 8:58 AM Bjorn Helgaas <helgaas@...nel.org> wrote:
> > On Mon, Jun 29, 2020 at 09:49:37PM -0700, Rajat Jain wrote:

> > > +static void pci_enable_acs(struct pci_dev *dev);
> >
> > I don't think we need this forward declaration, do we?
> 
> We need it unless we move its definition further up in the file:
> 
> drivers/pci/pci.c: In function ‘pci_restore_state’:
> drivers/pci/pci.c:1551:2: error: implicit declaration of function
> ‘pci_enable_acs’; did you mean ‘pci_enable_ats’?
> [-Werror=implicit-function-declaration]
>  1551 |  pci_enable_acs(dev);
> 
> Do you want me to move it up in the file so that we do not need the
> forward declaration?

Yes, please move it.  Maybe a preliminary patch that moves it but
doesn't change anything else.

I think I thought you had renamed the function, in which case you
could tell from the patch itself.  But I was mistaken!

> > > @@ -4653,7 +4653,7 @@ static int pci_quirk_intel_spt_pch_acs(struct pci_dev *dev, u16 acs_flags)
> > >       if (!pci_quirk_intel_spt_pch_acs_match(dev))
> > >               return -ENOTTY;
> > >
> > > -     pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS);
> > > +     pos = dev->acs_cap;
> >
> > I assume you verified that all these quirks are FINAL quirks, since
> > pci_init_capabilities() is called after HEADER quirks.  I'll
> > double-check before applying this.
> 
> None of these quirks are applied via DECLARE_PCI_FIXUP_*(). All these
> quirks are called (directly or indirectly) from either
> pci_enable_acs() or pci_acs_enabled(),
> 
> EXCEPT
> 
> pci_idt_bus_quirk(). That one is called from
> pci_bus_read_dev_vendor_id() which should be called only after the
> parent bridge has been added and setup correctly.
> 
> So it looks all good to me.

Great, thanks for checking that.