linux-kernel - Re: [PATCH v2 1/2] PCI/AER: Allow Native AER Host Bridges to use AER

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Date:   Thu, 23 Apr 2020 15:11:06 +0000
From:   "Derrick, Jonathan" <jonathan.derrick@...el.com>
To:     "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "helgaas@...nel.org" <helgaas@...nel.org>
CC:     "rajatja@...gle.com" <rajatja@...gle.com>,
        "kbusch@...nel.org" <kbusch@...nel.org>,
        "ruscur@...sell.cc" <ruscur@...sell.cc>,
        "fred@...dlawl.com" <fred@...dlawl.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "sbobroff@...ux.ibm.com" <sbobroff@...ux.ibm.com>,
        "olof@...om.net" <olof@...om.net>,
        "oohall@...il.com" <oohall@...il.com>,
        "mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "Patel, Mayurkumar" <mayurkumar.patel@...el.com>,
        "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] PCI/AER: Allow Native AER Host Bridges to use AER

Hi Sathyanarayanan,

On Wed, 2020-04-22 at 15:48 -0700, Kuppuswamy, Sathyanarayanan wrote:
> 
> On 4/20/20 2:37 PM, Jon Derrick wrote:
> > Some platforms have a mix of ports whose capabilities can be negotiated
> > by _OSC, and some ports which are not described by ACPI and instead
> > managed by Native drivers. The existing Firmware-First HEST model can
> > incorrectly tag these Native, Non-ACPI ports as Firmware-First managed
> > ports by advertising the HEST Global Flag and matching the type and
> > class of the port (aer_hest_parse).
> Is there a real use case for mixed mode (one host bridge in FF mode and
> another in native)?

Intel's VMD exposes PCIe segments containing Root Ports and Bridges and
other DPC consumers. These extra PCIe domains aren't described by ACPI.
There have been a few versions where DPC won't bind due to platform's
HEST configuration.

> > If the port requests Native AER through the Host Bridge's capability
> > settings, the AER driver should honor those settings and allow the port
> > to bind. This patch changes the definition of Firmware-First to exclude
> > ports whose Host Bridges request Native AER.
> > 
> > Signed-off-by: Jon Derrick <jonathan.derrick@...el.com>
> > ---
> >   drivers/pci/pcie/aer.c | 3 +++
> >   1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> > index f4274d3..30fbd1f 100644
> > --- a/drivers/pci/pcie/aer.c
> > +++ b/drivers/pci/pcie/aer.c
> > @@ -314,6 +314,9 @@ int pcie_aer_get_firmware_first(struct pci_dev *dev)
> >   	if (pcie_ports_native)
> >   		return 0;
> >   
> > +	if (pci_find_host_bridge(dev->bus)->native_aer)
> > +		return 0;
> > +
> >   	if (!dev->__aer_firmware_first_valid)
> >   		aer_set_firmware_first(dev);
> >   	return dev->__aer_firmware_first;
> >