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Re: [Qemu-devel] [PATCH v3] intel_iommu: check misordered init when real

From: Peter Xu
Subject: Re: [Qemu-devel] [PATCH v3] intel_iommu: check misordered init when realize
Date: Thu, 2 Mar 2017 13:20:53 +0800
User-agent: Mutt/1.5.24 (2015-08-30)

On Thu, Mar 02, 2017 at 07:13:08AM +0200, Michael S. Tsirkin wrote:
> On Thu, Mar 02, 2017 at 11:32:18AM +0800, Peter Xu wrote:
> > Intel vIOMMU devices are created with "-device" parameter, while here
> > actually we need to make sure the dmar device be created before other
> > PCI devices (like vfio-pci, virtio-pci ones) so that we know iommu_fn
> > will be setup correctly before realizations of those PCI devices (it is
> > legal that PCI device fetch these info during its realization). Now this
> > ordering yet cannot be achieved elsewhere, and devices will be created
> > in the order that user specified. We need to avoid that.
> > 
> > This patch tries to detect this kind of misordering issue during init of
> > VT-d device, then report to guest if misordering happened. In the
> > future, we can provide something better to solve it, e.g., to support
> > device init ordering, then we can live without this patch.
> > 
> > Signed-off-by: Peter Xu <address@hidden>
> Unfortunately with virtio it's a regression, as it used to
> work with iommu. So I'm afraid we need to look into supporting
> arbitrary order right now :(

No problem.

But do you think that would be a possible material for 2.9?


-- peterx

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