linux-kernel - Re: [PATCH] iommu: Implement deferred domain attachment

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Message-ID: <20200515142047.GX18353@8bytes.org>
Date:   Fri, 15 May 2020 16:20:48 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     iommu@...ts.linux-foundation.org, jroedel@...e.de,
        linux-kernel@...r.kernel.org, Tom Murphy <murphyt7@....ie>
Subject: Re: [PATCH] iommu: Implement deferred domain attachment

On Fri, May 15, 2020 at 09:51:03PM +0800, Lu Baolu wrote:
> On 2020/5/15 17:45, Joerg Roedel wrote:
> >   struct iommu_domain *iommu_get_dma_domain(struct device *dev)
> >   {
> > -	return dev->iommu_group->default_domain;
> > +	struct iommu_domain *domain = dev->iommu_group->default_domain;
> > +
> > +	if (__iommu_is_attach_deferred(domain, dev))
> > +		__iommu_attach_device_no_defer(domain, dev);
> 
> It seems that the return value needs to be checked. The default domain
> is invalid if attach() failed.

True, I looked at that, the callers can't handle returning NULL here, so
I kept it this way for now. The outcome is that DMA will fail, but
otherwise we'd see a NULL-ptr dereference really quickly after returning
from that function.

Bottom line: This needs to be cleaned up separatly.

Regards,

	Joerg