Re: [PATCH 3/5 v2] iommu/vt-d: Do deferred attachment in iommu_need_mapping()

[Jerry Snitselaar]

On Tue Feb 18 20, Joerg Roedel wrote:
> Hi Baolu,
>
> On Tue, Feb 18, 2020 at 10:38:14AM +0800, Lu Baolu wrote:
> > > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> > > index 42cdcce1602e..32f43695a22b 100644
> > > --- a/drivers/iommu/intel-iommu.c
> > > +++ b/drivers/iommu/intel-iommu.c
> > > @@ -2541,9 +2541,6 @@ static void do_deferred_attach(struct device *dev)
> > >   static struct dmar_domain *deferred_attach_domain(struct device *dev)
> > >   {
> > > -	if (unlikely(attach_deferred(dev)))
> > > -		do_deferred_attach(dev);
> > > -
> >
> > This should also be moved to the call place of deferred_attach_domain()
> > in bounce_map_single().
> >
> > bounce_map_single() assumes that devices always use DMA domain, so it
> > doesn't call iommu_need_mapping(). We could do_deferred_attach() there
> > manually.
>
> Good point, thanks for your review. Updated patch below.
>
> From 3a5b8a66d288d86ac1fd45092e7d96f842d0cccf Mon Sep 17 00:00:00 2001
> From: Joerg Roedel <jroedel@xxxxxxx>
> Date: Mon, 17 Feb 2020 17:20:59 +0100
> Subject: [PATCH 3/5] iommu/vt-d: Do deferred attachment in
> iommu_need_mapping()
>
> The attachment of deferred devices needs to happen before the check
> whether the device is identity mapped or not. Otherwise the check will
> return wrong results, cause warnings boot failures in kdump kernels, like
>
> 	WARNING: CPU: 0 PID: 318 at ../drivers/iommu/intel-iommu.c:592 domain_get_iommu+0x61/0x70
>
> 	[...]
>
> 	 Call Trace:
> 	  __intel_map_single+0x55/0x190
> 	  intel_alloc_coherent+0xac/0x110
> 	  dmam_alloc_attrs+0x50/0xa0
> 	  ahci_port_start+0xfb/0x1f0 [libahci]
> 	  ata_host_start.part.39+0x104/0x1e0 [libata]
>
> With the earlier check the kdump boot succeeds and a crashdump is written.
>
> Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>

Reviewed-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>