[libvirt] [PATCH 07/13] qemu: Add hotpluging support for PCI devices on S390 guests

Cornelia Huck cohuck at redhat.com
Fri Jun 1 07:44:44 UTC 2018


On Fri, 1 Jun 2018 12:43:09 +0800
Yi Min Zhao <zyimin at linux.ibm.com> wrote:

> 在 2018/5/29 下午5:04, Cornelia Huck 写道:
> > On Mon, 28 May 2018 16:26:57 +0800
> > Xiao Feng Ren <renxiaof at linux.vnet.ibm.com> wrote:

> >> As the model of Shmem is not support in qemu, the rng device doesn't
> >> support MSI-X.  So remove them.  
> > So, should qemu add support for msi-x with virtio-rng-pci in the
> > future, we'd want to update libvirt as well, correct?  
> This is a little bit hard to answer. Our patch adds the code calling the 
> function which is to
> attach zpci address in rng attachment function. As the logic in libvirt, 
> zpci could be generated
> for rng device. But it actually can't be supported in s390 qemu binary. 
> If it is being plugged,
> the error should be reported.
> 
> Thus, if we remove the attachement code for zpci in 
> qemuDomainAttachRNGDevice(),
> we should update libvirt when rng supports msix in qemu. If we keep it 
> here, then update for libvirt
> is not needed.

General question to the libvirt folks: is it better to just assume that
qemu can handle a device and deal with failure if it turns out that it
doesn't work after all, or to proactively fence off devices we assume
to not work? [Making virtio-rng-pci use msi-x in qemu does not look too
hard to do.]




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