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

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

On Sun, Sep 29, 2019 at 03:35:54AM +0200, Marek Marczykowski-Górecki wrote:
> On Thu, Sep 26, 2019 at 09:10:17AM +0200, Roger Pau Monné wrote:
> > 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).
> 
> Hmm, I see permissive is also set in sysfs
> (libxl_pci.c:pci_add_dm_done). And I think that is used by pciback,
> based on inspection of its source code.
> In fact, I don't see anything in pciback parsing opts-%d xenstore entry
> at all. It looks like it's only used by the toolstack to reconstruct
> libxl_device_pci struct from xenstore.

Then please use sysfs, using whatever mechanism is used by other
options seems fine to me.

Thanks, Roger.

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