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Marc Zyngier 146f76cc84 KVM: arm64: PMU: Fix per-CPU access in preemptible context 
Commit 07da1ffaa1 ("KVM: arm64: Remove host_cpu_context
member from vcpu structure") has, by removing the host CPU
context pointer, exposed that kvm_vcpu_pmu_restore_guest
is called in preemptible contexts:

[  266.932442] BUG: using smp_processor_id() in preemptible [00000000] code: qemu-system-aar/779
[  266.939721] caller is debug_smp_processor_id+0x20/0x30
[  266.944157] CPU: 2 PID: 779 Comm: qemu-system-aar Tainted: G            E     5.8.0-rc3-00015-g8d4aa58b2fe3 #1374
[  266.954268] Hardware name: amlogic w400/w400, BIOS 2020.04 05/22/2020
[  266.960640] Call trace:
[  266.963064]  dump_backtrace+0x0/0x1e0
[  266.966679]  show_stack+0x20/0x30
[  266.969959]  dump_stack+0xe4/0x154
[  266.973338]  check_preemption_disabled+0xf8/0x108
[  266.977978]  debug_smp_processor_id+0x20/0x30
[  266.982307]  kvm_vcpu_pmu_restore_guest+0x2c/0x68
[  266.986949]  access_pmcr+0xf8/0x128
[  266.990399]  perform_access+0x8c/0x250
[  266.994108]  kvm_handle_sys_reg+0x10c/0x2f8
[  266.998247]  handle_exit+0x78/0x200
[  267.001697]  kvm_arch_vcpu_ioctl_run+0x2ac/0xab8

Note that the bug was always there, it is only the switch to
using percpu accessors that made it obvious.
The fix is to wrap these accesses in a preempt-disabled section,
so that we sample a coherent context on trap from the guest.

Fixes: 435e53fb5e ("arm64: KVM: Enable VHE support for :G/:H perf event modifiers")
Cc:: Andrew Murray <amurray@thegoodpenguin.co.uk>
Signed-off-by: Marc Zyngier <maz@kernel.org>
2020-07-06 11:47:02 +01:00
arch KVM: arm64: PMU: Fix per-CPU access in preemptible context 2020-07-06 11:47:02 +01:00
block Kbuild updates for v5.8 (2nd) 2020-06-13 13:29:16 -07:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto Merge branch 'rwonce/rework' of git://git.kernel.org/pub/scm/linux/kernel/git/will/linux 2020-06-10 14:46:54 -07:00
Documentation Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-06-13 16:27:13 -07:00
drivers KVM: arm64: vgic-v4: Plug race between non-residency and v4.1 doorbell 2020-06-23 11:24:39 +01:00
fs for-5.8-part2-tag 2020-06-14 09:47:25 -07:00
include Add additional LSM hooks for SafeSetID 2020-06-14 11:39:31 -07:00
init Kbuild updates for v5.8 (2nd) 2020-06-13 13:29:16 -07:00
ipc mmap locking API: use coccinelle to convert mmap_sem rwsem call sites 2020-06-09 09:39:14 -07:00
kernel Add additional LSM hooks for SafeSetID 2020-06-14 11:39:31 -07:00
lib Kbuild updates for v5.8 (2nd) 2020-06-13 13:29:16 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm Kbuild updates for v5.8 (2nd) 2020-06-13 13:29:16 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-06-13 16:27:13 -07:00
samples binderfs: add gitignore for generated sample program 2020-06-13 13:41:24 -07:00
scripts Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-06-13 16:27:13 -07:00
security Add additional LSM hooks for SafeSetID 2020-06-14 11:39:31 -07:00
sound Kbuild updates for v5.8 (2nd) 2020-06-13 13:29:16 -07:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-06-13 16:27:13 -07:00
usr bpfilter: match bit size of bpfilter_umh to that of the kernel 2020-05-17 18:52:01 +09:00
virt MIPS: 2020-06-12 11:05:52 -07:00
.clang-format block: add bio_for_each_bvec_all() 2020-05-25 11:25:24 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore modpost: generate vmlinux.symvers and reuse it for the second modpost 2020-06-06 23:38:12 +09:00
.mailmap A fair amount of stuff this time around, dominated by yet another massive 2020-06-01 15:45:27 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS mailmap: change email for Ricardo Ribalda 2020-05-25 18:59:59 -06:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge branch 'i2c/for-5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2020-06-13 13:12:38 -07:00
Makefile Linux 5.8-rc1 2020-06-14 12:45:04 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

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

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    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.