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Filename Latest commit message Latest commit date
Paolo Bonzini 460df4c1fc KVM: race-free exit from KVM_RUN without POSIX signals
The purpose of the KVM_SET_SIGNAL_MASK API is to let userspace "kick"
a VCPU out of KVM_RUN through a POSIX signal.  A signal is attached
to a dummy signal handler; by blocking the signal outside KVM_RUN and
unblocking it inside, this possible race is closed:

          VCPU thread                     service thread
   --------------------------------------------------------------
        check flag
                                          set flag
                                          raise signal
        (signal handler does nothing)
        KVM_RUN

However, one issue with KVM_SET_SIGNAL_MASK is that it has to take
tsk->sighand->siglock on every KVM_RUN.  This lock is often on a
remote NUMA node, because it is on the node of a thread's creator.
Taking this lock can be very expensive if there are many userspace
exits (as is the case for SMP Windows VMs without Hyper-V reference
time counter).

As an alternative, we can put the flag directly in kvm_run so that
KVM can see it:

          VCPU thread                     service thread
   --------------------------------------------------------------
                                          raise signal
        signal handler
          set run->immediate_exit
        KVM_RUN
          check run->immediate_exit

Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-02-17 12:27:37 +01:00
arch KVM: race-free exit from KVM_RUN without POSIX signals 2017-02-17 12:27:37 +01:00
block blk-mq: Remove unused variable 2017-01-18 15:14:15 -07:00
certs
crypto
Documentation KVM: race-free exit from KVM_RUN without POSIX signals 2017-02-17 12:27:37 +01:00
drivers ptp_kvm: try to detect hypercall availability 2017-02-16 18:42:17 +01:00
firmware
fs Three filesystem endianness fixes (one goes back to the 2.6 era, all 2017-01-20 12:15:48 -08:00
include KVM: race-free exit from KVM_RUN without POSIX signals 2017-02-17 12:27:37 +01:00
init cgroup: move CONFIG_SOCK_CGROUP_DATA to init/Kconfig 2017-01-11 09:47:10 -05:00
ipc ipc/sem.c: fix incorrect sem_lock pairing 2017-01-10 18:31:55 -08:00
kernel Merge branch 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-01-22 12:45:47 -08:00
lib Merge branch 'stable/for-linus-4.10' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb 2017-01-17 09:27:50 -08:00
mm mm/hugetlb.c: fix reservation race when freeing surplus pages 2017-01-10 18:31:55 -08:00
net Three filesystem endianness fixes (one goes back to the 2.6 era, all 2017-01-20 12:15:48 -08:00
samples Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-01-15 11:37:43 -08:00
scripts
security
sound ASoC: Fixes for v4.10 2017-01-11 19:49:27 +01:00
tools kvmarm updates for 4.11 2017-02-09 16:01:23 +01:00
usr
virt KVM: Support vCPU-based gfn->hva cache 2017-02-16 18:42:46 +01:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap mailmap: add codeaurora.org names for nameless email commits 2017-01-10 18:31:55 -08:00
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS ARM: SoC fixes 2017-01-19 16:40:03 -08:00
Makefile Linux 4.10-rc5 2017-01-22 12:54:15 -08:00
README

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.