| Message ID | 20181108170558.17534-1-mfo@canonical.com |
|---|---|
| Headers | show |
| Series | Add kernel parameter 'pci=clearmsi' to clear MSI(X)s early on boot | expand |
Same considerations that I had for Xenial.
Hi, Mauricio. So, disco master-next does not correspond yet to our unstable development, which is already on top of 4.19. The patchset does not apply cleanly to unstable master branch. Can you submit for unstable, then? Thanks. Cascardo.
On Thu, Nov 8, 2018 at 3:21 PM Thadeu Lima de Souza Cascardo < cascardo@canonical.com> wrote: > Hi, Mauricio. > > So, disco master-next does not correspond yet to our unstable development, > which is already on top of 4.19. The patchset does not apply cleanly to > unstable master branch. Can you submit for unstable, then? > Sure; it will take a little while to build/test, but it should hit the list today as well. > Thanks. > Cascardo. >
BugLink: https://bugs.launchpad.net/bugs/1797990 (Note: the patch set for Cosmic/Disco should be identical, as both trees' master-next branch is at the 4.18.0-11.12 level, with some more patches in Cosmic, but doing Disco as well for process guidelines/completeness sake.) [Changelog] * v2: - Reorder patch 1 as 3 to allow for the next change: - Gate the bus-scan differences with the cmdline option (patch 3 only). Now all functional changes are gated. [Impact] * A kexec/crash kernel might get stuck and fail to boot (for crash kernel, kdump fails to collect a crashdump) if a PCI device is buggy/stuck/looping and triggers a continuous flood of MSI(X) interrupts (that the kernel does not yet know about). * This fix allowed to obtain crashdumps when debugging a heavy-load scenario, in which a (heavy-loaded) network adapter wouldn't stop triggering MSI-X interrupts ever after panic()->kdump kicked in. * This fix disables MSI(X) in all PCI devices on early boot (this is OK as it's (re-)enabled normally later) with a kernel cmdline parameter (disabled by default). [Test Case] * A synthetic test-case is not yet available, however, this particular system/workload triggered the problem consistently, and it was used for development/testing. * We'll update this bug once a synthetic test-case is available; we're working on patching QEMU for this. * $ dmesg | grep 'Clearing MSI' [ 0.000000] Clearing MSI/MSI-X enable bits early in boot (quirk) * The comparison of 'dmesg -t | sort' has been reviewed between option disabled/enabled on boot & kexec modes, and only expected differences found (MHz, PIDs, MIPS). [Regression Potential] * The potential area for regressions is early boot, particularly effects of applying quirks during PCI bus scan, which is changed/broader w/ these patches. * However, all quirks are applied based on PCI ID matching, so would only apply if actually targeting a new device. * Moreover, the new quirk is only applied based on a kernel cmdline parameter that is disabled by default, which constraints even more when this is actually in effect. [Other Info] * The patch series is still under review/discussion upstream, but it's relatively important for Ubuntu users at this point, and after internal discussions we decided to submit it for SRU. * These are links to the linux-pci archive with the patches [1, 2, 3] [1] [PATCH 1/3] x86/quirks: Scan all busses for early PCI quirks https://lore.kernel.org/linux-pci/20181018183721.27467-1-gpiccoli@canonical.com/ [2] [PATCH 2/3] x86/PCI: Export find_cap() to be used in early PCI code https://lore.kernel.org/linux-pci/20181018183721.27467-2-gpiccoli@canonical.com/ [3] [PATCH 3/3] x86/quirks: Add parameter to clear MSIs early on boot https://lore.kernel.org/linux-pci/20181018183721.27467-3-gpiccoli@canonical.com/ Guilherme G. Piccoli (3): UBUNTU: SAUCE: x86/PCI: Export find_cap() to be used in early PCI code UBUNTU: SAUCE: x86/quirks: Add parameter to clear MSIs early on boot UBUNTU: SAUCE: x86/quirks: Scan all busses for early PCI quirks .../admin-guide/kernel-parameters.txt | 6 +++ arch/x86/include/asm/pci-direct.h | 2 + arch/x86/kernel/aperture_64.c | 30 +------------- arch/x86/kernel/early-quirks.c | 41 +++++++++++++++++++ arch/x86/pci/common.c | 4 ++ arch/x86/pci/early.c | 25 +++++++++++ 6 files changed, 80 insertions(+), 28 deletions(-)