Re: [Xen-devel] [PATCH v3 1/6] libxl: do not attach xen-pciback to HVM domain, if stubdomain is in use

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Sat, Jan 26, 2019 at 03:31:12AM +0100, Marek Marczykowski-Górecki wrote:
> HVM domains use IOMMU and device model assistance for communicating with
> PCI devices, xen-pcifront/pciback isn't directly needed by HVM domain.
> But pciback serve also second function - it reset the device when it is
> deassigned from the guest and for this reason pciback needs to be used
> with HVM domain too.
> When HVM domain has device model in stubdomain, attaching xen-pciback to
> the target domain itself may prevent attaching xen-pciback to the
> (PV) stubdomain, effectively breaking PCI passthrough.
> 
> Fix this by attaching pciback only to one domain: if PV stubdomain is in
> use, let it be stubdomain (the commit prevents attaching device to target
> HVM in this case); otherwise, attach it to the target domain.
> 
> Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>

Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

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