Re: [PATCH v2] PCI/AER: Do not clear AER bits if we don't own AER

Alex G.
2018-07-24T15:59:37Z

On 07/23/2018 11:52 AM, Alexandru Gagniuc wrote:
> When we don't own AER, we shouldn't touch the AER error bits. Clearing
> error bits willy-nilly might cause firmware to miss some errors. In
> theory, these bits get cleared by FFS, or via ACPI _HPX method. These
> mechanisms are not subject to the problem.
>
> This race is mostly of theoretical significance, since I can't
> reasonably demonstrate this race in the lab.
>
> On a side-note, pcie_aer_is_kernel_first() is created to alleviate the
> need for two checks: aer_cap and get_firmware_first().
>
> Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
> ---
> drivers/pci/pcie/aer.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index a2e88386af28..85c3e173c025 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -307,6 +307,12 @@ int pcie_aer_get_firmware_first(struct pci_dev *dev)
> aer_set_firmware_first(dev);
> return dev->__aer_firmware_first;
> }
> +
> +static bool pcie_aer_is_kernel_first(struct pci_dev *dev)
> +{
> + return !!dev->aer_cap && !pcie_aer_get_firmware_first(dev);
> +}
> +
> #define PCI_EXP_AER_FLAGS (PCI_EXP_DEVCTL_CERE | PCI_EXP_DEVCTL_NFERE | \
> PCI_EXP_DEVCTL_FERE | PCI_EXP_DEVCTL_URRE)
>
> @@ -337,10 +343,7 @@ bool aer_acpi_firmware_first(void)
>
> int pci_enable_pcie_error_reporting(struct pci_dev *dev)
> {
> - if (pcie_aer_get_firmware_first(dev))
> - return -EIO;
> -
> - if (!dev->aer_cap)
> + if (!pcie_aer_is_kernel_first(dev))
> return -EIO;
>
> return pcie_capability_set_word(dev, PCI_EXP_DEVCTL, PCI_EXP_AER_FLAGS);
> @@ -349,7 +352,7 @@ EXPORT_SYMBOL_GPL(pci_enable_pcie_error_reporting);
>
> int pci_disable_pcie_error_reporting(struct pci_dev *dev)
> {
> - if (pcie_aer_get_firmware_first(dev))
> + if (!pcie_aer_is_kernel_first(dev))
> return -EIO;
>
> return pcie_capability_clear_word(dev, PCI_EXP_DEVCTL,
> @@ -383,10 +386,10 @@ int pci_cleanup_aer_error_status_regs(struct pci_dev *dev)
> if (!pci_is_pcie(dev))
> return -ENODEV;
>
> - pos = dev->aer_cap;
> - if (!pos)
> + if (pcie_aer_is_kernel_first(dev))

This here is missing a '!'. It's in my local branch, so I must have
exported the patch before I fixed that. I'll get that fixed next rev.

> return -EIO;
>
> + pos = dev->aer_cap;
> port_type = pci_pcie_type(dev);
> if (port_type == PCI_EXP_TYPE_ROOT_PORT) {
> pci_read_config_dword(dev, pos + PCI_ERR_ROOT_STATUS, &status);
>