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

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
>

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