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Filename Latest commit message Latest commit date
Thomas Gleixner f546965c3a x86/ioapic: Ignore IRQ2 again
commit a501b048a95b79e1e34f03cac3c87ff1e9f229ad upstream.

Vitaly ran into an issue with hotplugging CPU0 on an Amazon instance where
the matrix allocator claimed to be out of vectors. He analyzed it down to
the point that IRQ2, the PIC cascade interrupt, which is supposed to be not
ever routed to the IO/APIC ended up having an interrupt vector assigned
which got moved during unplug of CPU0.

The underlying issue is that IRQ2 for various reasons (see commit
af174783b9 ("x86: I/O APIC: Never configure IRQ2" for details) is treated
as a reserved system vector by the vector core code and is not accounted as
a regular vector. The Amazon BIOS has an routing entry of pin2 to IRQ2
which causes the IO/APIC setup to claim that interrupt which is granted by
the vector domain because there is no sanity check. As a consequence the
allocation counter of CPU0 underflows which causes a subsequent unplug to
fail with:

  [ ... ] CPU 0 has 4294967295 vectors, 589 available. Cannot disable CPU

There is another sanity check missing in the matrix allocator, but the
underlying root cause is that the IO/APIC code lost the IRQ2 ignore logic
during the conversion to irqdomains.

For almost 6 years nobody complained about this wreckage, which might
indicate that this requirement could be lifted, but for any system which
actually has a PIC IRQ2 is unusable by design so any routing entry has no
effect and the interrupt cannot be connected to a device anyway.

Due to that and due to history biased paranoia reasons restore the IRQ2
ignore logic and treat it as non existent despite a routing entry claiming
otherwise.

Fixes: d32932d02e ("x86/irq: Convert IOAPIC to use hierarchical irqdomain interfaces")
Reported-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210318192819.636943062@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-24 11:26:44 +01:00
arch x86/ioapic: Ignore IRQ2 again 2021-03-24 11:26:44 +01:00
block blk-settings: align max_sectors on "logical_block_size" boundary 2021-03-04 10:26:40 +01:00
certs certs: Fix blacklist flag type confusion 2021-03-04 10:26:29 +01:00
crypto crypto: x86 - Regularize glue function prototypes 2021-03-20 10:39:47 +01:00
Documentation KVM: arm64: Reject VM creation when the default IPA size is unsupported 2021-03-17 17:03:57 +01:00
drivers PCI: rpadlpar: Fix potential drc_name corruption in store functions 2021-03-24 11:26:43 +01:00
fs nfsd: Don't keep looking up unhashed files in the nfsd file cache 2021-03-24 11:26:38 +01:00
include USB: replace hardcode maximum usb string length by definition 2021-03-24 11:26:41 +01:00
init fgraph: Initialize tracing_graph_pause at task creation 2021-02-10 09:25:29 +01:00
ipc
kernel bpf: Add sanity check for upper ptr_limit 2021-03-20 10:39:46 +01:00
lib PCI: Fix pci_register_io_range() memory leak 2021-03-17 17:03:44 +01:00
LICENSES
mm Revert "mm, slub: consider rest of partial list if acquire_slab() fails" 2021-03-17 17:03:34 +01:00
net net/qrtr: fix __netdev_alloc_skb call 2021-03-24 11:26:39 +01:00
samples samples, bpf: Add missing munmap in xdpsock 2021-03-17 17:03:33 +01:00
scripts ftrace: Have recordmcount use w8 to read relp->r_info in arm64_is_fake_mcount 2021-03-09 11:09:39 +01:00
security Revert 95ebabde382c ("capabilities: Don't allow writing ambiguous v3 file capabilities") 2021-03-17 17:03:47 +01:00
sound ASoC: simple-card-utils: Do not handle device clock 2021-03-24 11:26:37 +01:00
tools bpf, selftests: Fix up some test_verifier cases for unprivileged 2021-03-20 10:39:46 +01:00
usr
virt KVM: arm64: Ensure I-cache isolation between vcpus of a same VM 2021-03-17 17:03:57 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile kbuild: Fix <linux/version.h> for empty SUBLEVEL or PATCHLEVEL again 2021-03-24 11:26:39 +01:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
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In order to build the documentation, use ``make htmldocs`` or
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    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.