Hi, I'm helping out Dell work out through the issues related to PCIe and NVMe hotplug. Although hot-plug generally works, there are corner cases such as pin bounce, drives failing and surprise removal that are not 100% worked out. Because of this, NVMe is not yet on feature parity with SCSI and SAS. One of the interesting issues is that most server vendors like to use firmware-first (FFS), for various reasons that I won't go into. The side effect of that is that we oftentimes don't even a stab at correcting the problem. This is especially troublesome for NVMe, which needs PCIe hotplug to work correctly. When we do get a stab, it's after FFS can't handle a fatal error, and we're told of it through ACPI tables. On x86, this happens through an NMI, and as soon as we see a "fatal" error, we panic(). One problem with this FFS approach is that AER never even gets notified of the issue. And even if a PCIe drive were to stop responding, nvme or higher block drivers would notice something is wrong even without AER. Unless there is a physical defect or silicon bug, AER can recover the link. Another issue we're seeing with FFS is that BIOSes assume than an OS will crash on a fatal error reported through ACPI. Sometimes they will leave hardware in a "kind of" working state, or will fail to re-arm the errors. From what I've observed, this happens on hardware with silicon bugs. For example, PCIe root ports are unaffected, but certain PCIe switches may stop issuing hotplug interrupts. It's just another headache with FFS. While I don't expect server vendors to drop FFS in favor of native AER control, I do think we can harden linux against the idiosyncrasies of such systems. The scope of these patches is to protect against poorly designed firmware, and perform proper error handling when possible. It is not to make FFS a first class citizen in error handling. Alexandru Gagniuc (4): acpi: apei: Return severity of GHES messages after handling acpi: apei: Swap ghes_print_queued_estatus and ghes_proc_in_irq acpi: apei: Do not panic() in NMI because of GHES messages acpi: apei: Warn when GHES marks correctable errors as "fatal" drivers/acpi/apei/ghes.c | 100 ++++++++++++++++++++++++++++++----------------- 1 file changed, 64 insertions(+), 36 deletions(-) -- 2.14.3 -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
