[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 16/23] hyperv: map overlay pages after updating
From: |
Roman Kagan |
Subject: |
Re: [Qemu-devel] [PATCH 16/23] hyperv: map overlay pages after updating msrs |
Date: |
Wed, 14 Jun 2017 15:41:10 +0300 |
User-agent: |
Mutt/1.8.0 (2017-02-23) |
On Wed, Jun 14, 2017 at 02:11:56PM +0200, Paolo Bonzini wrote:
> On 14/06/2017 13:54, Roman Kagan wrote:
> >> Why not disable the zeroing for host-initiated MSR writes? This is
> >> pretty clearly a KVM bug, we can push it to stable kernels too.
> >
> > The only problem with this is that QEMU will have no reliable way to
> > know if the KVM it runs with has this bug fixed or not. Machines
> > without vmbus work and even migrate fine with the current KVM despite
> > this bug (the only user of those pages currently is synic timers which
> > re-arm themselves and post messages regardless of zeroing). Now
> > updating QEMU to a vmbus-enabled version without updating the kernel
> > will make the migrations cause guest hangs.
>
> Return 2 from KVM_CHECK_EXTENSION(KVM_CAP_HYPERV_SYNIC)? Then you can
> make new QEMU refuse to enable synic if a new kernel is not available.
Indeed, that's a possibility.
I'll probably make it in both directions then: on
KVM_ENABLE_CAP(KVM_CAP_HYPERV_SYNIC, 2) disable zeroing completely,
including on guest writes, to better match Hyper-V. Or does it deserve
a separate cap number?
Thanks,
Roman.
- [Qemu-devel] [PATCH 18/23] hyperv: add synic event flag signaling, (continued)
- [Qemu-devel] [PATCH 18/23] hyperv: add synic event flag signaling, Roman Kagan, 2017/06/06
- [Qemu-devel] [PATCH 17/23] hyperv: add synic message delivery, Roman Kagan, 2017/06/06
- [Qemu-devel] [PATCH 22/23] MAINTAINERS: add myself and eyakovlev@ for hyperv*, Roman Kagan, 2017/06/06
- [Qemu-devel] [PATCH 20/23] hyperv: process POST_MESSAGE hypercall, Roman Kagan, 2017/06/06
- [Qemu-devel] [PATCH 21/23] hyperv_testdev: add SynIC message and event testmodes, Roman Kagan, 2017/06/06
- [Qemu-devel] [PATCH 16/23] hyperv: map overlay pages after updating msrs, Roman Kagan, 2017/06/06
[Qemu-devel] [PATCH 23/23] hyperv: update copyright notices, Roman Kagan, 2017/06/06
Message not available