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Fri, 25 Sep 2020 18:07:39 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3020.oracle.com with ESMTP id 33nury487e-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 25 Sep 2020 18:07:39 +0000 Received: from abhmp0011.oracle.com (abhmp0011.oracle.com [141.146.116.17]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 08PI7bx2018317; Fri, 25 Sep 2020 18:07:37 GMT Received: from [10.39.220.177] (/10.39.220.177) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 25 Sep 2020 11:07:37 -0700 Subject: Re: [PATCH V1 10/32] kvmclock: restore paused KVM clock To: "Dr. David Alan Gilbert" References: <1596122076-341293-1-git-send-email-steven.sistare@oracle.com> <1596122076-341293-11-git-send-email-steven.sistare@oracle.com> <20200911175018.GP3310@work-vm> From: Steven Sistare Organization: Oracle Corporation Message-ID: Date: Fri, 25 Sep 2020 14:07:33 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20200911175018.GP3310@work-vm> Content-Type: text/plain; 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Berrange" , "Michael S. Tsirkin" , =?UTF-8?Q?Alex_Benn=c3=a9e?= , Juan Quintela , qemu-devel@nongnu.org, Markus Armbruster , Alex Williamson , Stefan Hajnoczi , =?UTF-8?Q?Marc-Andr=c3=a9_Lureau?= , Paolo Bonzini , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 9/11/2020 1:50 PM, Dr. David Alan Gilbert wrote: > * Steve Sistare (steven.sistare@oracle.com) wrote: >> If the VM is paused when the KVM clock is serialized to a file, record >> that the clock is valid, so the value will be reused rather than >> overwritten after cprload with a new call to KVM_GET_CLOCK here: >> >> kvmclock_vm_state_change() >> if (running) >> ... >> else >> if (s->clock_valid) >> return; <-- instead, return here >> >> kvm_update_clock() >> kvm_vm_ioctl(kvm_state, KVM_GET_CLOCK, &data) <-- overwritten >> >> Signed-off-by: Steve Sistare >> --- >> hw/i386/kvm/clock.c | 6 +++++- >> 1 file changed, 5 insertions(+), 1 deletion(-) >> >> diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c >> index 6428335..161991a 100644 >> --- a/hw/i386/kvm/clock.c >> +++ b/hw/i386/kvm/clock.c >> @@ -285,18 +285,22 @@ static int kvmclock_pre_save(void *opaque) >> if (!s->runstate_paused) { >> kvm_update_clock(s); >> } >> + if (!runstate_is_running()) { >> + s->clock_valid = true; >> + } >> >> return 0; >> } >> >> static const VMStateDescription kvmclock_vmsd = { >> .name = "kvmclock", >> - .version_id = 1, >> + .version_id = 2, >> .minimum_version_id = 1, >> .pre_load = kvmclock_pre_load, >> .pre_save = kvmclock_pre_save, >> .fields = (VMStateField[]) { >> VMSTATE_UINT64(clock, KVMClockState), >> + VMSTATE_BOOL_V(clock_valid, KVMClockState, 2), >> VMSTATE_END_OF_LIST() > > We always try and avoid bumping version_id unless we're > desperate because it breaks backwards migration. > > Didn't you already know from the stored migration state > (in the globalstate) if the loaded VM was running? > > It's also not clear to me why you're avoiding reloading the state; > have you preserved that some other way? This patch was needed only for an early version of cprload which had some gratuitous vmstate transitions. I will happily drop this patch. - Steve >> }, >> .subsections = (const VMStateDescription * []) { >> -- >> 1.8.3.1 >>