v3 -> v2: Modified the text that describes the problem v2 -> v1: Returned -EPERM v1 : http://marc.info/?l=linux-pci&m=130013194803727&w=2 For servers whose hardware cannot handle ASPM the BIOS ought to set the FADT bit shown below: In Sec 5.2.9.3 (IA-PC Boot Arch. Flags) of ACPI4.0a Specification, please see Table 5-11: PCIe ASPM Controls: If set, indicates to OSPM that it must not enable OPSM ASPM control on this platform. However there are shipping servers whose BIOS did not set this bit. (An example is the HP ProLiant DL385 G6. A Maintenance BIOS will fix that). For such servers even if a call is made via pci_no_aspm(), based on _OSC support in the BIOS, it may be too late because the ASPM code may have already allocated and filled its "link_list". So if a user sets the ASPM "policy" to "powersave" via /sys then pcie_aspm_set_policy() will run through the "link_list" and re-configure ASPM policy on devices that advertise ASPM L0s/L1 capability: # echo powersave > /sys/module/pcie_aspm/parameters/policy # cat /sys/module/pcie_aspm/parameters/policy default performance [powersave] That can cause NMIs since the hardware doesn't play well with ASPM: [ 1651.906015] NMI: PCI system error (SERR) for reason b1 on CPU 0. [ 1651.906015] Dazed and confused, but trying to continue Ideally, the BIOS should have set that FADT bit in the first place but we could be more robust - especially given the fact that Windows doesn't cause NMIs in the above scenario. There should be a sanity check to not allow a user to modify ASPM policy when aspm_disabled is set. Signed-off-by: Naga Chumbalkar <nagananda.chumbalkar@xxxxxx> Acked-by: Rafael J. Wysocki <rjw@xxxxxxx> Cc: Matthew Garrett <mjg59@xxxxxxxxxxxxx> --- drivers/pci/pcie/aspm.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c index e768620..7ab61ac 100644 --- a/drivers/pci/pcie/aspm.c +++ b/drivers/pci/pcie/aspm.c @@ -769,6 +769,8 @@ static int pcie_aspm_set_policy(const char *val, struct kernel_param *kp) int i; struct pcie_link_state *link; + if (aspm_disabled) + return -EPERM; for (i = 0; i < ARRAY_SIZE(policy_str); i++) if (!strncmp(val, policy_str[i], strlen(policy_str[i]))) break; @@ -823,6 +825,8 @@ static ssize_t link_state_store(struct device *dev, struct pcie_link_state *link, *root = pdev->link_state->root; u32 val = buf[0] - '0', state = 0; + if (aspm_disabled) + return -EPERM; if (n < 1 || val > 3) return -EINVAL; -- 1.7.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
