Re: [RFC + Queries] Flow of PCI passthrough in ARM

From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: manish jaggi <manishjaggi.oss@gmail.com>
Cc: Ryan Wilson <hap9@epoch.ncsc.mil>,
	Ian Campbell <Ian.Campbell@citrix.com>,
	Vijay Kilari <vijay.kilari@gmail.com>,
	Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
	Prasun Kapoor <prasun.Kapoor@caviumnetworks.com>,
	manish.jaggi@caviumnetworks.com,
	Julien Grall <julien.grall@linaro.org>,
	xen-devel <xen-devel@lists.xen.org>,
	JBeulich@suse.com
Subject: Re: [RFC + Queries] Flow of PCI passthrough in ARM
Date: Thu, 6 Nov 2014 14:41:48 -0500	[thread overview]
Message-ID: <20141106194148.GD5906@laptop.dumpdata.com> (raw)
In-Reply-To: <CAAiw7JkFmZVK80QO7ux2Sq0=6m5=-JZfGQf6FEDxgQ=ULpPVpA@mail.gmail.com>

On Thu, Nov 06, 2014 at 08:58:18PM +0530, manish jaggi wrote:
> On 20 October 2014 20:24, Stefano Stabellini
> <stefano.stabellini@eu.citrix.com> wrote:
> > On Mon, 20 Oct 2014, manish jaggi wrote:
> >> On 8 October 2014 20:21, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:
> >> > On Wed, Oct 08, 2014 at 07:17:48PM +0530, manish jaggi wrote:
> >> >> On 8 October 2014 19:15, Ian Campbell <Ian.Campbell@citrix.com> wrote:
> >> >> > On Wed, 2014-10-08 at 19:07 +0530, manish jaggi wrote:
> >> >> >> Thanks for replying. As detailed in this thread, I need to create a
> >> >> >> hypercall that would send the following information to Xen at the time
> >> >> >> of PCI attach
> >> >> >> { sbdf , domU sbdf, domainId }.
> >> >> >> I am not able to find a way to get the domU sbdf from dom0 at the time
> >> >> >> of pci-attach.
> >> >> >
> >> >> > I think it would need to be done by the pciback driver in the dom0
> >> >> > kernel, which AFAIK is the thing which consistently knows both physical
> >> >> > and virtual sbdf for a given assigned device.
> >> >> >
> >> >> > Ian.
> >> >> >
> >> >> Correct, can you point out which data structure holds the domU sbdf
> >> >> corresponding to the actual sbdf in pciback.
> >> >
> >> > See 'xen_pcibk_export_device' or 'xen_pcibk_publish_pci_root'
> >> > is that what you are referring to?
> >>
> >> Xen docs also mention about xen-pciback.passthrough=1. If I set this
> >> in dom0 i see that the device is enumerated as the same sbdf in domU,
> >> but
> >> a) it is not shown in lspci
> >> b) no front-back communication is done for reading devices configuration space
> >> .
> >> Is option useful / fully implemented for ARM ?
> >
> > I don't think this option is very useful. I wouldn't worry about it for
> > now.
> 
> Stefano / Ian / Konard / Julien,
> 
> Attached is a first raw code FYI RFC Patches of PCI passthrough support on ARM.
> - Linux Patch (3.18)

I would move the code that arch/arm64/xen/xen_pci.c introduces
(which is also in arch/x86/pci/xen.c) in its own generic file - say
to drivers/xen/pci.c.

That way you share the code between those two platforms instead
of copying it.

> - Xen Patch  (4.5 staging)
> ---(Smmu changes not included, thats a separate patch altogether)
> This patches show the logic, at places need of improvements in code
> organization/quality. I wanted to share to get initial comments.
> This is working with SRIOV as well.

Fantastic!
> 
> Please have a look and let me know your positive comments