From: =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>
Subject: [PATCH v2 0/5] KVM: optimize userspace exits with a new ioctl
Date: Wed,  5 Aug 2015 18:32:56 +0200
Message-Id: <1438792381-19453-1-git-send-email-rkrcmar@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1903
Lines: 47

v2:
 * move request_exits debug counter patch right after introduction of
   KVM_REQ_EXIT [3/5]
 * use vcpu ioctl instead of vm one [4/5]
 * shrink kvm_user_exit from 64 to 32 bytes [4/5]
 * new [5/5]

QEMU uses SIGUSR1 to force a userspace exit and also to queue an early
exit before calling VCPU_RUN -- the signal is blocked in user space and
temporarily unblocked in VCPU_RUN.
The temporal unblocking by sigprocmask() in kvm_arch_vcpu_ioctl_run()
takes a shared siglock, which leads to cacheline bouncing in NUMA
systems.

This series allows the same with a new request bit and VM IOCTL that
marks and kicks target VCPU, hence no need to unblock.

inl_from_{pmtimer,qemu} vmexit benchmark from kvm-unit-tests shows ~5%
speedup for 1-4 VCPUs (300-2000 saved cycles) without noticeably
regressing kernel VM exits.
(Paolo did a quick run of older version of this series on a NUMA system
 and the speedup was around 35% when utilizing more nodes.)

Radim Krčmář (5):
  KVM: add kvm_has_request wrapper
  KVM: add KVM_REQ_EXIT request for userspace exit
  KVM: x86: add request_exits debug counter
  KVM: add KVM_USER_EXIT vcpu ioctl for userspace exit
  KVM: refactor asynchronous vcpu ioctl dispatch

 Documentation/virtual/kvm/api.txt | 30 ++++++++++++++++++++++++++++++
 arch/x86/include/asm/kvm_host.h   |  1 +
 arch/x86/kvm/vmx.c                |  4 ++--
 arch/x86/kvm/x86.c                | 32 ++++++++++++++++++++++++++++++++
 include/linux/kvm_host.h          | 15 +++++++++++++--
 include/uapi/linux/kvm.h          |  8 ++++++++
 virt/kvm/kvm_main.c               | 14 +++++++++-----
 7 files changed, 95 insertions(+), 9 deletions(-)

-- 
2.5.0

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/