Re: [PATCH] iommu: check for the deferred attach when attaching a device

[Robin Murphy]

On 2021-01-05 07:52, lijiang wrote:
> 在 2021年01月05日 11:55, lijiang 写道:
> > Hi,
> >
> > Also add Joerg to cc list.
>
> Also add more people to cc list, Jerry Snitselaar and Tom Lendacky.
>
> Thanks.
>
> > Thanks.
> > Lianbo
> > 在 2020年12月26日 13:39, Lianbo Jiang 写道:
> > > Currently, because domain attach allows to be deferred from iommu
> > > driver to device driver, and when iommu initializes, the devices
> > > on the bus will be scanned and the default groups will be allocated.
> > >
> > > Due to the above changes, some devices could be added to the same
> > > group as below:
> > >
> > > [    3.859417] pci 0000:01:00.0: Adding to iommu group 16
> > > [    3.864572] pci 0000:01:00.1: Adding to iommu group 16
> > > [    3.869738] pci 0000:02:00.0: Adding to iommu group 17
> > > [    3.874892] pci 0000:02:00.1: Adding to iommu group 17
> > >
> > > But when attaching these devices, it doesn't allow that a group has
> > > more than one device, otherwise it will return an error. This conflicts
> > > with the deferred attaching. Unfortunately, it has two devices in the
> > > same group for my side, for example:
> > >
> > > [    9.627014] iommu_group_device_count(): device name[0]:0000:01:00.0
> > > [    9.633545] iommu_group_device_count(): device name[1]:0000:01:00.1
> > > ...
> > > [   10.255609] iommu_group_device_count(): device name[0]:0000:02:00.0
> > > [   10.262144] iommu_group_device_count(): device name[1]:0000:02:00.1
> > >
> > > Finally, which caused the failure of tg3 driver when tg3 driver calls
> > > the dma_alloc_coherent() to allocate coherent memory in the tg3_test_dma().
> > >
> > > [    9.660310] tg3 0000:01:00.0: DMA engine test failed, aborting
> > > [    9.754085] tg3: probe of 0000:01:00.0 failed with error -12
> > > [    9.997512] tg3 0000:01:00.1: DMA engine test failed, aborting
> > > [   10.043053] tg3: probe of 0000:01:00.1 failed with error -12
> > > [   10.288905] tg3 0000:02:00.0: DMA engine test failed, aborting
> > > [   10.334070] tg3: probe of 0000:02:00.0 failed with error -12
> > > [   10.578303] tg3 0000:02:00.1: DMA engine test failed, aborting
> > > [   10.622629] tg3: probe of 0000:02:00.1 failed with error -12
> > >
> > > In addition, the similar situations also occur in other drivers such
> > > as the bnxt_en driver. That can be reproduced easily in kdump kernel
> > > when SME is active.
> > >
> > > Add a check for the deferred attach in the iommu_attach_device() and
> > > allow to attach the deferred device regardless of how many devices
> > > are in a group.

Is this iommu_attach_device() call is coming from iommu-dma? (if not, 
then whoever's calling it probably shouldn't be)

Assuming so, then probably what should happen is to move the handling 
currently in iommu_dma_deferred_attach() into the core so that it can 
call __iommu_attach_device() directly - the intent is just to replay 
that exact call skipped in iommu_group_add_device(), so the legacy 
external iommu_attach_device() interface isn't really the right tool for 
the job anyway. That's just slightly awkward since ideally it wants to 
be done in a way that doesn't result in a redundant out-of-line call for 
!kdump.

Alternatively I suppose it *could* just call ops->attach_dev directly, 
but then we miss out on the tracepoint, and deferred attach is arguably 
one of the cases where that's most useful :/

Robin.

> > > Signed-off-by: Lianbo Jiang <lijiang@xxxxxxxxxx>
> > > ---
> > >   drivers/iommu/iommu.c | 5 ++++-
> > >   1 file changed, 4 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > > index ffeebda8d6de..dccab7b133fb 100644
> > > --- a/drivers/iommu/iommu.c
> > > +++ b/drivers/iommu/iommu.c
> > > @@ -1967,8 +1967,11 @@ int iommu_attach_device(struct iommu_domain *domain, struct device *dev)
> > >   	 */
> > >   	mutex_lock(&group->mutex);
> > >   	ret = -EINVAL;
> > > -	if (iommu_group_device_count(group) != 1)
> > > +	if (!iommu_is_attach_deferred(domain, dev) &&
> > > +	    iommu_group_device_count(group) != 1) {
> > > +		dev_err_ratelimited(dev, "Group has more than one device\n");
> > >   		goto out_unlock;
> > > +	}
> > >   
> > >   	ret = __iommu_attach_group(domain, group);
> > >   
>
> _______________________________________________
> iommu mailing list
> iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
> https://lists.linuxfoundation.org/mailman/listinfo/iommu