Re: [Xen-devel] [PATCH v7 4/4] xen/x86: Allow stubdom access to irq created for msi.

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Sep 26, 2019 at 06:16:06AM +0200, Marek Marczykowski-Górecki wrote:
> On Wed, Sep 25, 2019 at 03:26:17PM +0200, Roger Pau Monné wrote:
> > On Wed, Sep 25, 2019 at 02:29:41PM +0200, Marek Marczykowski-Górecki wrote:
> > > On Wed, Sep 25, 2019 at 11:41:50AM +0200, Roger Pau Monné wrote:
> > > > It would still be nice to get the missing bits (interrupt enabling),
> > > > or else this patch is kind of pointless, since it still doesn't allow
> > > > stubdomains to work correctly with passed through devices.
> > > 
> > > Well, that part, as discussed, doesn't need to be in Xen. For example
> > > the solution deployed in current Qubes stable version is based on
> > > pciback for this purpose.
> > 
> > Ack. Do you think it would make sense to submit that part to Linux
> > then?
> 
> How would an interface with toolstack (when to allow enabling MSI)
> should look like? Right now I have it as extra attribute in sysfs of
> pciback and libxl writes to it. Or rather should it be in xenstore?

I think xenstore would be more suitable for this. There are already
some flags passed to pciback there: msitranslate, power_mgmt and
permissive (see libxl_pci.c:63).

> Or maybe pciback should somehow detect itself if it's talking to
> stubdomain while the device is assigned to a HVM domain, or to a target
> PV domain itself?

I think doing it in the toolstack and just passing an option to
pciback is likely easier than adding more logic to pciback.

Thanks, Roger.

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