From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754181AbbIBLca (ORCPT ); Wed, 2 Sep 2015 07:32:30 -0400 Received: from e06smtp10.uk.ibm.com ([195.75.94.106]:56707 "EHLO e06smtp10.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752138AbbIBLc2 (ORCPT ); Wed, 2 Sep 2015 07:32:28 -0400 X-Helo: d06dlp01.portsmouth.uk.ibm.com X-MailFrom: borntraeger@de.ibm.com X-RcptTo: linux-kernel@vger.kernel.org Message-ID: <55E6D009.9040000@de.ibm.com> Date: Wed, 02 Sep 2015 12:31:37 +0200 From: Christian Borntraeger User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0 MIME-Version: 1.0 To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , linux-kernel@vger.kernel.org CC: kvm@vger.kernel.org, Paolo Bonzini Subject: Re: [PATCH v3 0/5] KVM: optimize userspace exits with a new ioctl References: <1439546917-17391-1-git-send-email-rkrcmar@redhat.com> In-Reply-To: <1439546917-17391-1-git-send-email-rkrcmar@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15090211-0041-0000-0000-000005788258 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 14.08.2015 um 12:08 schrieb Radim Krčmář: > v3: > * acked by Christian [1/5] > * use ioctl argument directly (unsigned long as flags) [4/5] > * precisely #ifdef arch-specific ioctls [5/5] > 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 | 25 +++++++++++++++++++++++++ > arch/x86/include/asm/kvm_host.h | 1 + > arch/x86/kvm/vmx.c | 4 ++-- > arch/x86/kvm/x86.c | 23 +++++++++++++++++++++++ > include/linux/kvm_host.h | 15 +++++++++++++-- > include/uapi/linux/kvm.h | 4 ++++ > virt/kvm/kvm_main.c | 15 ++++++++++----- > 7 files changed, 78 insertions(+), 9 deletions(-) > As far as I can see this should also work for s390 (when we implement REQ_EXIT handling) To double check my understanding: these improvements come with a changed userspace that does not use KVM_SET_SIGNAL_MASK and therefore this conditional is false if (vcpu->sigset_active) sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved); Correct? That also means we improve exits that go to userspace but lightweight exits that stay inside the kernel are not affected. Correct? Christian