Re: [PATCH v1 1/1] hw/pci: Disable PCI_ERR_UNCOR_MASK register for machine type < 8.0

[Jiri Denemark]

On Thu, May 11, 2023 at 13:43:47 +0200, Juan Quintela wrote:
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> [Added libvirt people to the party, see the end of the message ]

Sorry, I'm not that much into parties :-)

> That would fix the:
> 
> qemu-8.0 -M pc-7.2 -> qemu-8.0.1 -M pc-7.2
> 
> It is worth it?  Dunno.  That is my question.
> 
> And knowing from what qemu it has migrated from would not help.  We
> would need to add a new tweak and means:
> 
> This is a pc-7.2 machine that has been isntantiated in a qemu-8.0 and
> has the pciaerr bug.  But wait, we have _that_.
> 
> And it is called
> 
> +    { TYPE_PCI_DEVICE, "x-pcie-err-unc-mask", "off" },
> 
> from the patch.
> 
> We can teach libvirt about this glitch, and if he is migrating a pc-7.2
> machine in qemu-8.0 machine, And they want to migrate to a new qemu
> (call it qemu-8.1), it needs to be started:
> 
> qemu-8.1 -M pc-7.2 <whatever pci devices need to do>,x-pci-err-unc-mask="true"
> 
> Until the user reboots it and then that property can be reset to default
> value.

Hmm and what would happen if eventually this machine gets migrated back
to qemu-8.0? Or even when the machine is stopped, started again, and
then migrated to qemu-8.0?

Jirka