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SubjectRe: [PATCH v1 1/1] PCI/AER: Use _OSC negotiation to determine AER ownership
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Hi Bjorn,

On 4/30/2020 3:40 PM, Bjorn Helgaas wrote:
> [+cc Austin, Mario, Jon, Alex, Rafael, Keith, Sinan, Tyler]
>
> On Sun, Apr 26, 2020 at 11:30:06AM -0700, sathyanarayanan.kuppuswamy@linux.intel.com wrote:
>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>>
>> Currently PCIe AER driver uses HEST FIRMWARE_FIRST bit to
>> determine the PCIe AER Capability ownership between OS and
>> firmware. This support is added based on following spec
>> reference.
>>
>> Per ACPI spec r6.3, table 18-387, 18-388, 18-389, HEST table
>> flags field BIT-0 and BIT-1 can be used to expose the
>> ownership of error source between firmware and OSPM.
>>
>> Bit [0] - FIRMWARE_FIRST: If set, indicates that system
>> firmware will handle errors from this source
>> first.
>> Bit [1] – GLOBAL: If set, indicates that the settings
>> contained in this structure apply globally to all
>> PCI Express Bridges.
>>
>> Although above spec reference states that setting
>> FIRMWARE_FIRST bit means firmware will handle the error source
>> first, it does not explicitly state anything about AER
>> ownership. So using HEST to determine AER ownership is
>> incorrect.
>>
>> Also, as per following specification references, _OSC can be
>> used to negotiate the AER ownership between firmware and OS.
>> Details are,
>>
>> Per ACPI spec r6.3, sec 6.2.11.3, table titled “Interpretation
>> of _OSC Control Field” and as per PCI firmware specification r3.2,
>> sec 4.5.1, table 4-5, OS can set bit 3 of _OSC control field
>> to request control over PCI Express AER. If the OS successfully
>> receives control of this feature, it must handle error reporting
>> through the AER Capability as described in the PCI Express Base
>> Specification.
>>
>> Since above spec references clearly states _OSC can be used to
>> determine AER ownership, don't depend on HEST FIRMWARE_FIRST bit.
>
> I pulled out the _OSC part of this to a separate patch. What's left
> is below, and is essentially equivalent to Alex's patch:
>
> https://lore.kernel.org/r/20190326172343.28946-3-mr.nuke.me@gmail.com/
>
> I like what this does, but what I don't like is the fact that we now
> have this thing called pcie_aer_get_firmware_first() that is not
> connected with the ACPI FIRMWARE_FIRST bit at all.
I agree. Since the current function has nothing to do with firmware
first check, we can rename it. May be pci_aer_is_native() ?
>
> I think the end result will be more readable if we get rid of the
> "firmware_first" completely. I don't know if we need a wrapper for it
> at all, or if we should just open-code:
Since pcie_aer_get_firmware_first() is used in following exported
functions, I think we still need to check for "pcie_ports_native"
and "pci_is_pcie()"

pci_enable_pcie_error_reporting()
pci_disable_pcie_error_reporting()
pci_cleanup_aer_uncorrect_error_status()
pci_aer_clear_fatal_status()
pci_cleanup_aer_error_status_regs()
>
> int pci_enable_pcie_error_reporting(struct pci_dev *dev)
> {
> struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
>
> if (!host->native_aer)
> return -EIO;
>
> It's of nice to minimize the number of things you have look at.
> We already have native_aer, aer_cap, pcie_ports_native,
> pci_aer_available(), ..., so maybe we can live with seeing
> pci_find_host_bridge() a few times.
>
>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
>> index f4274d301235..85d73d28ec26 100644
>> --- a/drivers/pci/pcie/aer.c
>> +++ b/drivers/pci/pcie/aer.c
>> @@ -217,133 +217,19 @@ void pcie_ecrc_get_policy(char *str)
>> }
>> #endif /* CONFIG_PCIE_ECRC */
>>
>> -#ifdef CONFIG_ACPI_APEI
>> -static inline int hest_match_pci(struct acpi_hest_aer_common *p,
>> - struct pci_dev *pci)
>> -{
>> - return ACPI_HEST_SEGMENT(p->bus) == pci_domain_nr(pci->bus) &&
>> - ACPI_HEST_BUS(p->bus) == pci->bus->number &&
>> - p->device == PCI_SLOT(pci->devfn) &&
>> - 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;
>> -};
>> -
>> -static int hest_source_is_pcie_aer(struct acpi_hest_header *hest_hdr)
>> -{
>> - if (hest_hdr->type == ACPI_HEST_TYPE_AER_ROOT_PORT ||
>> - hest_hdr->type == ACPI_HEST_TYPE_AER_ENDPOINT ||
>> - hest_hdr->type == ACPI_HEST_TYPE_AER_BRIDGE)
>> - return 1;
>> - return 0;
>> -}
>> -
>> -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;
>> -
>> - if (!hest_source_is_pcie_aer(hest_hdr))
>> - return 0;
>> -
>> - p = (struct acpi_hest_aer_common *)(hest_hdr + 1);
>> - ff = !!(p->flags & ACPI_HEST_FIRMWARE_FIRST);
>> -
>> - /*
>> - * If no specific device is supplied, determine whether
>> - * FIRMWARE_FIRST is set for *any* PCIe device.
>> - */
>> - if (!info->pci_dev) {
>> - info->firmware_first |= ff;
>> - return 0;
>> - }
>> -
>> - /* Otherwise, check the specific device */
>> - if (p->flags & ACPI_HEST_GLOBAL) {
>> - if (hest_match_type(hest_hdr, info->pci_dev))
>> - info->firmware_first = ff;
>> - } else
>> - if (hest_match_pci(p, info->pci_dev))
>> - info->firmware_first = ff;
>> -
>> - return 0;
>> -}
>> -
>> -static void aer_set_firmware_first(struct pci_dev *pci_dev)
>> -{
>> - int rc;
>> - struct aer_hest_parse_info info = {
>> - .pci_dev = pci_dev,
>> - .firmware_first = 0,
>> - };
>> -
>> - rc = apei_hest_parse(aer_hest_parse, &info);
>> -
>> - if (rc)
>> - pci_dev->__aer_firmware_first = 0;
>> - else
>> - pci_dev->__aer_firmware_first = info.firmware_first;
>> - pci_dev->__aer_firmware_first_valid = 1;
>> -}
>> -
>> int pcie_aer_get_firmware_first(struct pci_dev *dev)
>> {
>> + struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
>> +
>> if (!pci_is_pcie(dev))
>> return 0;
>>
>> if (pcie_ports_native)
>> return 0;
>>
>> - if (!dev->__aer_firmware_first_valid)
>> - aer_set_firmware_first(dev);
>> - return dev->__aer_firmware_first;
>> + return !host->native_aer;
>> }
>
>> diff --git a/drivers/pci/pcie/portdrv.h b/drivers/pci/pcie/portdrv.h
>> index 64b5e081cdb2..c05b49d740f4 100644
>> --- a/drivers/pci/pcie/portdrv.h
>> +++ b/drivers/pci/pcie/portdrv.h
>> @@ -147,16 +147,7 @@ static inline bool pcie_pme_no_msi(void) { return false; }
>> static inline void pcie_pme_interrupt_enable(struct pci_dev *dev, bool en) {}
>> #endif /* !CONFIG_PCIE_PME */
>>
>> -#ifdef CONFIG_ACPI_APEI
>> int pcie_aer_get_firmware_first(struct pci_dev *pci_dev);
>> -#else
>> -static inline int pcie_aer_get_firmware_first(struct pci_dev *pci_dev)
>> -{
>> - if (pci_dev->__aer_firmware_first_valid)
>> - return pci_dev->__aer_firmware_first;
>> - return 0;
>> -}
>> -#endif
>>
>> struct device *pcie_port_find_device(struct pci_dev *dev, u32 service);
>> #endif /* _PORTDRV_H_ */
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index 83ce1cdf5676..43f265830eca 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -420,8 +420,6 @@ struct pci_dev {
>> * mappings to make sure they cannot access arbitrary memory.
>> */
>> unsigned int untrusted:1;
>> - unsigned int __aer_firmware_first_valid:1;
>> - unsigned int __aer_firmware_first:1;
>> unsigned int broken_intx_masking:1; /* INTx masking can't be used */
>> unsigned int io_window_1k:1; /* Intel bridge 1K I/O windows */
>> unsigned int irq_managed:1;
>> --
>> 2.17.1
>>

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer

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