From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH] Guest stop notification Date: Thu, 01 Dec 2011 18:35:17 +0100 Message-ID: <4ED7BAD5.8020105@siemens.com> References: <1322602574-27072-1-git-send-email-emunson@mgebm.net> <4ED79138.60603@siemens.com> <20111201171938.GA8803@mgebm.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "ryanh@linux.vnet.ibm.com" , "aliguori@us.ibm.com" , "kvm@vger.kernel.org" , "mtosatti@redhat.com" , "qemu-devel@nongnu.org" , "linux-kernel@vger.kernel.org" , "avi@redhat.com" To: Eric B Munson Return-path: In-Reply-To: <20111201171938.GA8803@mgebm.net> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org Sender: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org List-Id: kvm.vger.kernel.org On 2011-12-01 18:19, Eric B Munson wrote: > On Thu, 01 Dec 2011, Jan Kiszka wrote: > >> On 2011-11-29 22:36, Eric B Munson wrote: >>> Often when a guest is stopped from the qemu console, it will >>> report spurious soft lockup warnings on resume. There are >>> kernel patches being discussed that will give the host the >>> ability to tell the guest that it is being stopped and should >>> ignore the soft lockup warning that generates. >>> >>> Signed-off-by: Eric B Munson Cc: >>> ryanh@linux.vnet.ibm.com Cc: aliguori@us.ibm.com Cc: >>> mtosatti@redhat.com Cc: avi@redhat.com Cc: kvm@vger.kernel.org >>> Cc: linux-kernel@vger.kernel.org --- target-i386/kvm.c | 6 >>> ++++++ 1 files changed, 6 insertions(+), 0 deletions(-) >>> >>> diff --git a/target-i386/kvm.c b/target-i386/kvm.c index >>> 5bfc21f..defd364 100644 --- a/target-i386/kvm.c +++ >>> b/target-i386/kvm.c @@ -336,12 +336,18 @@ static int >>> kvm_inject_mce_oldstyle(CPUState *env) return 0; } >>> >>> +static void kvm_put_guest_paused(CPUState *penv) +{ + >>> kvm_vcpu_ioctl(penv, KVM_GUEST_PAUSED, 0); +} >> >> I see no need in encapsulating this in a separate function. >> > > The encapsulated function was from a previous idea, I will remove > it for V2. > >>> + static void cpu_update_state(void *opaque, int running, >>> RunState state) { CPUState *env = opaque; >>> >>> if (running) { env->tsc_valid = false; + >>> kvm_put_guest_paused(env); >> >> checkpatch.pl would have asked you to remove this tab. > > Will change to spaces for V2. > >> >> More general: >> >> Why is this x86-only? If the kernel interface is x86-only, what >> prevents making it generic right from the beginning? >> >> Why do we need a new IOCTL for this? Was there no space left in >> the kvm_run structure e.g. to pass this flag down on next vcpu >> execution? No big deal, just wondering. > > Thanks for your review/feedback. > > When I started looking into this problem, the ioctl was the first > suggestion I got for how to communicate from qemu to guest kernel. > I don't see a technical reason that this could not be added to the > kvm_run structure in one of the bytes currently used as padding. I > would prefer to keep the ioctl because I have the corresponding > kernel patches out to work with this, however, if there is a strong > preference for using kvm_run, I can rework both sets. My feeling is that a run field would be more elegant, but I might be wrong on this as well. In any case: You need KVM_CAP in your kernel interface to announce the new feature and you have to sync in the new kernel header into QEMU to make it build. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux