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

From: "Roger Pau Monné" <roger.pau@citrix.com>
To: "Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>
Cc: Kevin Tian <kevin.tian@intel.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Jan Beulich <jbeulich@suse.com>, Wei Liu <wl@xen.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	George Dunlap <George.Dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>, Tim Deegan <tim@xen.org>,
	Simon Gaiser <simon@invisiblethingslab.com>,
	Julien Grall <julien.grall@arm.com>,
	Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
	xen-devel@lists.xenproject.org, Brian Woods <brian.woods@amd.com>
Subject: Re: [Xen-devel] [PATCH v7 4/4] xen/x86: Allow stubdom access to irq created for msi.
Date: Mon, 30 Sep 2019 10:17:18 +0200	[thread overview]
Message-ID: <20190930081718.bij2lrh7fvavwtws@Air-de-Roger> (raw)
In-Reply-To: <20190929013554.GA24160@mail-itl>

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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