From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Gregory Haskins" Subject: Re: [PATCH 10/10] KVM: Adds support for halting in the kernel Date: Thu, 24 May 2007 07:54:08 -0400 Message-ID: <46554473.BA47.005A.0@novell.com> References: <20070523130905.23177.11087.stgit@novell1.haskins.net> <20070523131932.23177.38587.stgit@novell1.haskins.net> <46554CFF.9040101@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: "Avi Kivity" Return-path: In-Reply-To: <46554CFF.9040101-atKUWr5tajBWk0Htik3J/w@public.gmane.org> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org >>> On Thu, May 24, 2007 at 4:29 AM, in message <46554CFF.9040101-atKUWr5tajBWk0Htik3J/w@public.gmane.org>, Avi Kivity wrote: > Gregory Haskins wrote: >> Halting in userspace requires a relatively cumbersome mechanism to signal > the >> halted VCPU. Implementing halt in kernel should be relatively straight >> forward and it eliminates the need for the signaling >> >> /* >> + * The vCPU has executed a HLT instruction with in- kernel mode enabled. >> + */ >> +static int kvm_vcpu_kern_halt(struct kvm_vcpu *vcpu, struct kvm_run > *kvm_run) >> +{ >> + DECLARE_WAITQUEUE(wait, current); >> + sigset_t sigblocked, sigsaved; >> + int r = 1; >> + >> + /* >> + * Unmask all signals while we wait >> + */ >> + memset(&sigblocked, 0, sizeof(sigblocked)); >> + sigprocmask(SIG_SETMASK, &sigblocked, &sigsved); >> > > We have a specialized signal mask for the kernel, and it is already in > effect here. See KVM_SET_SIGNAL_MASK. > KVM_SET_SIGNAL_MASK is precisely what I was trying to counteract ;). Basically I was thinking that userspace could have set some arbitrary mask that would be in effect at this time. My justification for unmasking everything is two fold: 1) I think I really want *any* signal to kick the HLT, so I temporarily unmask everything while halted. 2) Old userspace halting would not have the SET_SIGNAL_MASK set at the time either, since we would have restored the original mask before returning to userspace. That being said, I am not an expert here so I may have got it wrong. Please advise. -Greg ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/