Re: [Xen-devel] [PATCH v2] xen/passthrough: Support a single iommu_domain per xen domain per SMMU

[Manish Jaggi <mjaggi@xxxxxxxxxxxxxxxxxx>]

On Wednesday 25 March 2015 11:05 PM, Stefano Stabellini wrote:
> On Wed, 25 Mar 2015, Manish Jaggi wrote:
> > On Tuesday 24 March 2015 07:34 PM, Robert VanVossen wrote:
> > > On 3/24/2015 7:07 AM, Manish Jaggi wrote:
> > > > On Monday 23 March 2015 07:16 PM, Robbie VanVossen wrote:
> > > > > If multiple devices are being passed through to the same domain and they
> > > > > share a single SMMU, then they only require a single iommu_domain.
> > > > >
> > > > > In arm_smmu_assign_dev, before a new iommu_domain is created, the
> > > > > xen_domain->contexts is checked for any iommu_domains that are already
> > > > > assigned to device that uses the same SMMU as the current device. If one
> > > > > is found, attach the device to that iommu_domain. If a new one isn't
> > > > > found, create a new iommu_domain just like before.
> > > > >
> > > > > The arm_smmu_deassign_dev function assumes that there is a single
> > > > > device per iommu_domain. This meant that when the first device was
> > > > > deassigned, the iommu_domain was freed and when another device was
> > > > > deassigned a crash occured in xen.
> > > > >
> > > > > To fix this, a reference counter was added to the iommu_domain struct.
> > > > > When an arm_smmu_xen_device references an iommu_domain, the
> > > > > iommu_domains ref is incremented. When that reference is removed, the
> > > > > iommu_domains ref is decremented. The iommu_domain will only be freed
> > > > > when the ref is 0.
> > > > >
> > > > > Signed-off-by: Robbie VanVossen <robert.vanvossen@xxxxxxxxxxxxxxx>
> > > > Hi,
> > > > Are you adding a PCI passthrough support to Xen ?. I am in process of
> > > > sending smmu driver patches based on juliens latest code.
> > > Nope, I am just working on what this patch describes
> > Your patch is doing similar thing what am working on. As per the Xen 4.6
> > release I took smmu for pci-passthorugh. I didnt send smmu patches so far as
> > there are other dependency patches I need to send first like pci_host_bridge
> > register hypercall patch.
> >
> > Julien/Ian could you please hold the merge of this patch.
> Sorry Manish, but the Xen community works on a first come first served
> basis:  if/when this patch is considered in good condition and ready to
> be merged, is likely to be merged.
> Unless you have a specific concern about the code of course.
Ok. I will incorporate robert's patch in my patch set.
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