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Filename Latest commit message Latest commit date
Joao Martins 132194ffa1 KVM: VMX: Do not change PID.NDST when loading a blocked vCPU
When vCPU enters block phase, pi_pre_block() inserts vCPU to a per pCPU
linked list of all vCPUs that are blocked on this pCPU. Afterwards, it
changes PID.NV to POSTED_INTR_WAKEUP_VECTOR which its handler
(wakeup_handler()) is responsible to kick (unblock) any vCPU on that
linked list that now has pending posted interrupts.

While vCPU is blocked (in kvm_vcpu_block()), it may be preempted which
will cause vmx_vcpu_pi_put() to set PID.SN.  If later the vCPU will be
scheduled to run on a different pCPU, vmx_vcpu_pi_load() will clear
PID.SN but will also *overwrite PID.NDST to this different pCPU*.
Instead of keeping it with original pCPU which vCPU had entered block
phase on.

This results in an issue because when a posted interrupt is delivered, as
the wakeup_handler() will be executed and fail to find blocked vCPU on
its per pCPU linked list of all vCPUs that are blocked on this pCPU.
Which is due to the vCPU being placed on a *different* per pCPU
linked list i.e. the original pCPU in which it entered block phase.

The regression is introduced by commit c112b5f502 ("KVM: x86:
Recompute PID.ON when clearing PID.SN"). Therefore, partially revert
it and reintroduce the condition in vmx_vcpu_pi_load() responsible for
avoiding changing PID.NDST when loading a blocked vCPU.

Fixes: c112b5f502 ("KVM: x86: Recompute PID.ON when clearing PID.SN")
Tested-by: Nathan Ni <nathan.ni@oracle.com>
Co-developed-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2019-11-12 10:17:41 +01:00
arch KVM: VMX: Do not change PID.NDST when loading a blocked vCPU 2019-11-12 10:17:41 +01:00
block
certs
crypto
Documentation
drivers ARM: SoC fixes 2019-11-10 13:41:59 -08:00
fs configfs regression fix for 5.4-rc 2019-11-10 12:59:34 -08:00
include ARM: SoC fixes 2019-11-10 13:41:59 -08:00
init
ipc
kernel Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-11-10 12:03:58 -08:00
lib
LICENSES
mm
net
samples
scripts
security
sound
tools Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-11-10 11:55:53 -08:00
usr
virt KVM: fix placement of refcount initialization 2019-11-11 15:48:03 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS ARM: SoC fixes 2019-11-10 13:41:59 -08:00
Makefile Linux 5.4-rc7 2019-11-10 16:17:15 -08:00
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.