From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [QEMU PATCH] kvmclock: advance clock by time window between vm_stop and pre_save Date: Fri, 4 Nov 2016 16:33:33 +0100 Message-ID: <1c69a083-eef0-8fa0-0e74-5a4e25a066a0@redhat.com> References: <20161104094322.GA16930@amt.cnet> <20161104152522.GC5388@potion> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: kvm@vger.kernel.org, qemu-devel , "Dr. David Alan Gilbert" , Juan Quintela , Eduardo Habkost , Roman Kagan To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Marcelo Tosatti Return-path: Received: from mx1.redhat.com ([209.132.183.28]:38374 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932150AbcKDPdj (ORCPT ); Fri, 4 Nov 2016 11:33:39 -0400 In-Reply-To: <20161104152522.GC5388@potion> Sender: kvm-owner@vger.kernel.org List-ID: On 04/11/2016 16:25, Radim Krčmář wrote: >> > >> > + if (s->advance_clock && s->clock + s->advance_clock > s->clock) { >> > + s->clock += s->advance_clock; >> > + s->advance_clock = 0; >> > + } > Can't the advance_clock added to the migrated KVMClockState instead of > passing it as another parameter? > > (It is sad that we can't just query KVMClockState in kvmclock_pre_save > because of the Linux bug.) What Linux bug? The one that makes us use kvmclock_current_nsec? It should work with 4.9-rc (well, once Linus applies my pull request). 4.9-rc will not return ktime_get_ns for KVM_GET_CLOCK; it will return the raw value from the kernel timekeeper. I'm thinking that we should add a KVM capability for this, and skip kvmclock_current_nsec if the capability is present. The first part is trivial, so we can do it even during Linux rc period. Paolo