Re: [PATCH v2 1/3] PCI/AER: Fix incorrect return from aer_hest_parse()

Chen Gong
2013-06-05T02:56:05Z

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On Tue, Jun 04, 2013 at 07:13:24AM -0600, Bjorn Helgaas wrote:
> Date: Tue, 4 Jun 2013 07:13:24 -0600
> From: Bjorn Helgaas <bhelgaas@google.com>
> To: Betty Dall <betty.dall@hp.com>
> Cc: rjw@sisk.pl, ying.huang@intel.com, linux-acpi@vger.kernel.org,
> linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
> gong.chen@linux.intel.com
> Subject: Re: [PATCH v2 1/3] PCI/AER: Fix incorrect return from
> aer_hest_parse()
> User-Agent: Mutt/1.5.21 (2010-09-15)
>
> On Thu, May 30, 2013 at 08:39:27AM -0600, Betty Dall 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@hp.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;
>
>
> 1) I think dev->__aer_firmware_first should be initialized somewhere in the
> pci_scan_single_device() path, e.g., maybe pci_init_capabilities(). It's
> known at device add-time and never changes, so there's no point in doing
> the lazy setup we do now. That would let us get rid of
> __aer_firmware_first_valid, too (along with the pointless "__" prefix).
> This is just an observation, not a requirement for this patch set.
>
> 2) This is a band-aid that covers up the real problem, which is that we
> update info->firmware_first even for non-matching devices. I think we
> should do something like the following instead:
>
>
> commit c67612f272f1792a08f012f1b5ca37d5cfde5de4
> Author: Bjorn Helgaas <bhelgaas@google.com>
> Date: Mon Jun 3 16:49:12 2013 -0600
>
> PCI/AER: Don't parse HEST table for non-PCIe devices
>
> AER is a PCIe-only capability, so there's no point in trying to match
> a HEST PCIe structure with a non-PCIe device.
>
> Previously, a HEST global AER bridge entry (type 8) could incorrectly
> match *any* bridge, even a legacy PCI-PCI bridge, and a non-global
> HEST entry could match a legacy PCI device.
>
If so, it should be a BIOS bug, right? (BIOS should not contain PCI device
for AER structure).
And I agree that your patch tries to avoid this scenario, but even one PCI
device is set FFM enabled, as you mentioned above, AER is only for PCIe,
which means a PCI device will not trigger such an event, so it should be
harmless, in principle. But in practice, I totally agree with you that
should be fixed.

Reviewed-by: Chen Gong <gong.chen@linux.intel.com>

> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
>
> diff --git a/drivers/pci/pcie/aer/aerdrv_acpi.c b/drivers/pci/pcie/aer/aerdrv_acpi.c
> index 5194a7d..4f798ab 100644
> --- a/drivers/pci/pcie/aer/aerdrv_acpi.c
> +++ b/drivers/pci/pcie/aer/aerdrv_acpi.c
> @@ -59,8 +59,7 @@ static int aer_hest_parse(struct acpi_hest_header *hest_hdr, void *data)
>
> p = (struct acpi_hest_aer_common *)(hest_hdr + 1);
> if (p->flags & ACPI_HEST_GLOBAL) {
> - if ((pci_is_pcie(info->pci_dev) &&
> - pci_pcie_type(info->pci_dev) == pcie_type) || bridge)
> + if ((pci_pcie_type(info->pci_dev) == pcie_type) || bridge)
> ff = !!(p->flags & ACPI_HEST_FIRMWARE_FIRST);
> } else
> if (hest_match_pci(p, info->pci_dev))
> @@ -89,6 +88,9 @@ static void aer_set_firmware_first(struct pci_dev *pci_dev)
>
> int pcie_aer_get_firmware_first(struct pci_dev *dev)
> {
> + if (!pci_is_pcie(dev))
> + return 0;
> +
> if (!dev->__aer_firmware_first_valid)
> aer_set_firmware_first(dev);
> return dev->__aer_firmware_first;
>
> commit 947da50270686b0d70f4bc2f7323ef7229489ecb
> Author: Bjorn Helgaas <bhelgaas@google.com>
> Date: Mon Jun 3 15:42:00 2013 -0600
>
> PCI/AER: Factor out HEST device type matching
>
> This factors out the matching of HEST structure type and PCIe device type
> to improve readability. No functional change.
>
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
>

Reviewed-by: Chen Gong <gong.chen@linux.intel.com>

> diff --git a/drivers/pci/pcie/aer/aerdrv_acpi.c b/drivers/pci/pcie/aer/aerdrv_acpi.c
> index 4f798ab..56e2d94 100644
> --- a/drivers/pci/pcie/aer/aerdrv_acpi.c
> +++ b/drivers/pci/pcie/aer/aerdrv_acpi.c
> @@ -29,6 +29,22 @@ static inline int hest_match_pci(struct acpi_hest_aer_common *p,
> p->function == PCI_FUNC(pci->devfn));
> }
>
> +static inline bool hest_match_type(struct acpi_hest_header *hest_hdr,
> + struct pci_dev *dev)
> +{
> + u16 hest_type = hest_hdr->type;
> + u8 pcie_type = pci_pcie_type(dev);
> +
> + if ((hest_type == ACPI_HEST_TYPE_AER_ROOT_PORT &&
> + pcie_type == PCI_EXP_TYPE_ROOT_PORT) ||
> + (hest_type == ACPI_HEST_TYPE_AER_ENDPOINT &&
> + pcie_type == PCI_EXP_TYPE_ENDPOINT) ||
> + (hest_type == ACPI_HEST_TYPE_AER_BRIDGE &&
> + (dev->class >> 16) == PCI_BASE_CLASS_BRIDGE))
> + return true;
> + return false;
> +}
> +
> struct aer_hest_parse_info {
> struct pci_dev *pci_dev;
> int firmware_first;
> @@ -38,28 +54,11 @@ static int aer_hest_parse(struct acpi_hest_header *hest_hdr, void *data)
> {
> struct aer_hest_parse_info *info = data;
> struct acpi_hest_aer_common *p;
> - u8 pcie_type = 0;
> - u8 bridge = 0;
> int ff = 0;
>
> - switch (hest_hdr->type) {
> - case ACPI_HEST_TYPE_AER_ROOT_PORT:
> - pcie_type = PCI_EXP_TYPE_ROOT_PORT;
> - break;
> - case ACPI_HEST_TYPE_AER_ENDPOINT:
> - pcie_type = PCI_EXP_TYPE_ENDPOINT;
> - break;
> - case ACPI_HEST_TYPE_AER_BRIDGE:
> - if ((info->pci_dev->class >> 16) == PCI_BASE_CLASS_BRIDGE)
> - bridge = 1;
> - break;
> - default:
> - return 0;
> - }
> -
> p = (struct acpi_hest_aer_common *)(hest_hdr + 1);
> if (p->flags & ACPI_HEST_GLOBAL) {
> - if ((pci_pcie_type(info->pci_dev) == pcie_type) || bridge)
> + if (hest_match_type(hest_hdr, info->pci_dev))
> ff = !!(p->flags & ACPI_HEST_FIRMWARE_FIRST);
> } else
> if (hest_match_pci(p, info->pci_dev))
>
> commit e9f977a04d96a54c4f6aa0b831e725dab2154364
> Author: Bjorn Helgaas <bhelgaas@google.com>
> Date: Mon Jun 3 19:47:27 2013 -0600
>
> PCI/AER: Set dev->__aer_firmware_first only for matching devices
>
> Previously, we always updated info->firmware_first, even for HEST entries
> that didn't match the device. Therefore, if the last HEST descriptor was
> a PCIe structure that didn't match the device, we always cleared
> dev->__aer_firmware_first.
>
> Based-on-patch-by: Betty Dall <betty.dall@hp.com>
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

Reviewed-by: Chen Gong <gong.chen@linux.intel.com>

> diff --git a/drivers/pci/pcie/aer/aerdrv_acpi.c b/drivers/pci/pcie/aer/aerdrv_acpi.c
> index 56e2d94..2bedad8 100644
> --- a/drivers/pci/pcie/aer/aerdrv_acpi.c
> +++ b/drivers/pci/pcie/aer/aerdrv_acpi.c
> @@ -54,16 +54,16 @@ static int aer_hest_parse(struct acpi_hest_header *hest_hdr, void *data)
> {
> struct aer_hest_parse_info *info = data;
> struct acpi_hest_aer_common *p;
> - int ff = 0;
> + int ff;
>
> p = (struct acpi_hest_aer_common *)(hest_hdr + 1);
> - if (p->flags & ACPI_HEST_GLOBAL) {
> + ff = !!(p->flags & ACPI_HEST_FIRMWARE_FIRST);
> + if (p->flags & ACPI_HEST_GLOBAL)
> if (hest_match_type(hest_hdr, info->pci_dev))
> - ff = !!(p->flags & ACPI_HEST_FIRMWARE_FIRST);
> - } else
> + info->firmware_first = ff;
> + else
> if (hest_match_pci(p, info->pci_dev))
> - ff = !!(p->flags & ACPI_HEST_FIRMWARE_FIRST);
> - info->firmware_first = ff;
> + info->firmware_first = ff;
>
> return 0;
> }

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