From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH v3 2/5] KVM: add KVM_REQ_EXIT request for userspace exit Date: Sat, 22 Aug 2015 00:04:55 -0700 Message-ID: <55D81F17.8000907@redhat.com> References: <1439546917-17391-1-git-send-email-rkrcmar@redhat.com> <1439546917-17391-3-git-send-email-rkrcmar@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, Christian Borntraeger To: Wanpeng Li , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , linux-kernel@vger.kernel.org Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 19/08/2015 20:55, Wanpeng Li wrote: >> The disadvantage is that it adds an overhead of one bit check for all >> kernel exits. A quick tracing shows that the ratio of userspace exits >> after boot is about 1/5 and in subsequent run of nmap and kernel compile >> has about 1/60, so the check should not regress global performance. >> >> All signal_pending() calls are userspace exit requests, so we add a >> check for KVM_REQ_EXIT there. There is one omitted call in kvm_vcpu_run >> because KVM_REQ_EXIT is implied in earlier check for requests. > > Actually I see more SIGUSR1 signals are intercepted by signal_pending() > in vcpu_enter_guest() and vcpu_run() w/ win7 guest and kernel_irqchip=off. You need more patches on the QEMU side. I tested a version that is mostly okay but not ready for upstream inclusion. Paolo