linux-kernel - Re: [PATCH v2 1/3] PCI/AER: Fix incorrect return from aer_hest

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Message-ID: <CAErSpo6e_3Xy3F0z2L0LCdQoShc=VkLTsS6+icYkhsexiqgQMQ@mail.gmail.com>
Date:	Tue, 4 Jun 2013 11:39:00 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Betty Dall <betty.dall@...com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Huang Ying <ying.huang@...el.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"Moore, Robert" <robert.moore@...el.com>
Subject: Re: [PATCH v2 1/3] PCI/AER: Fix incorrect return from aer_hest_parse()

On Mon, Jun 3, 2013 at 3:18 PM, Betty Dall <betty.dall@...com> wrote:
> On Sat, 2013-06-01 at 18:38 -0600, Bjorn Helgaas wrote:
>> [+cc Bob for ACPI HEST spec questions]
>>
>> On Thu, May 30, 2013 at 8:39 AM, Betty Dall <betty.dall@...com> wrote:
>> > The function aer_hest_parse() is called to determine if the given
>> > PCI device is firmware first or not. The code loops through each
>> > section of the HEST table to look for a match. The bug is that
>> > the function always returns whether the last HEST section is firmware
>> > first. The fix stops the iteration once the info.firmware_first
>> > variable is set.  This is similar to how the function aer_hest_parse_aff()
>> > stops the iteration.
>> >
>> > Signed-off-by: Betty Dall <betty.dall@...com>
>> > ---
>> >
>> >  drivers/pci/pcie/aer/aerdrv_acpi.c |    3 +++
>> >  1 files changed, 3 insertions(+), 0 deletions(-)
>> >
>> >
>> > diff --git a/drivers/pci/pcie/aer/aerdrv_acpi.c b/drivers/pci/pcie/aer/aerdrv_acpi.c
>> > index 5194a7d..39b8671 100644
>> > --- a/drivers/pci/pcie/aer/aerdrv_acpi.c
>> > +++ b/drivers/pci/pcie/aer/aerdrv_acpi.c
>> > @@ -42,6 +42,9 @@ static int aer_hest_parse(struct acpi_hest_header *hest_hdr, void *data)
>> >         u8 bridge = 0;
>> >         int ff = 0;
>> >
>> > +       if (info->firmware_first)
>> > +               return 0;
>> > +
>> >         switch (hest_hdr->type) {
>> >         case ACPI_HEST_TYPE_AER_ROOT_PORT:
>> >                 pcie_type = PCI_EXP_TYPE_ROOT_PORT;
>>
>> Not related directly to your patch, Betty, but I can't figure out why
>> the ACPI spec defines the HEST structures for PCIe as it does.  I'm
>> looking at ACPI 5.0, sec 18.3.2.3 - 18.3.2.5.
>
>> 1) The PCIe Root Port, PCIe Device, and PCIe/PCI-X Bridge structures
>> all include Bus, Device, and Function fields.  But there's no Segment.
>>  The current Linux code (hest_match_pci()) assumes HEST records can
>> only apply to PCI domain 0.  Is Linux missing something, or is the
>> HEST really this limited?
> You are right that the HEST table does not have the Segment for the PCIe
> sources. The Linux code uses the Generic Source type that points to a
> UEFI CPER record. Those do have the Segment. The code in
> acpi/apei/ghes.c that parses the HEST and invokes the
> aer_recover_queue() is using the segment from the CPER record.

My question has nothing to do with CPER.  Drivers can enable error
reporting for their devices with pci_enable_pcie_error_reporting().
If the device is marked "firmware-first" in the HEST, this call fails
without enabling reporting.  The HEST can only mark devices in domain
0 as "firmware-first."  Therefore pci_enable_pcie_error_reporting()
will enable reporting for:

  - domain 0 devices not marked "firmware-first" and
  - all devices in other domains.

This inconsistency seems like a hole in the spec, but maybe I'm
missing something.

Bjorn
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