On 21/03/17 17:21, Will Deacon wrote:
> On Tue, Mar 21, 2017 at 04:45:27PM +0100, Joerg Roedel wrote:
>> On Fri, Mar 10, 2017 at 08:49:36PM +0000, Will Deacon wrote:
>>> @@ -1014,8 +1027,8 @@ struct iommu_group *iommu_group_get_for_dev(struct
>>> device *dev)
>>> * IOMMU driver.
>>> */
>>> if (!group->default_domain) {
>>> - group->default_domain = __iommu_domain_alloc(dev->bus,
>>> - IOMMU_DOMAIN_DMA);
>>> + group->default_domain =
>>> + __iommu_domain_alloc(dev->bus, iommu_def_domain_type);
>>
>> It would be good to have a fall-back here if we are talking to an IOMMU
>> driver that uses default domains, but does not support identity-mapped
>> domains (yet). Exynos and Rockchip IOMMU drivers seem to fall into this
>> category. A dev_warn() also makes sense in case allocating a identity
>> domain fails.
>
> Sure, something like the diff below?
>
> Will
>
> --->8
>
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 42a842e3f95f..f787626a745d 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1027,10 +1027,19 @@ struct iommu_group *iommu_group_get_for_dev(struct
> device *dev)
> * IOMMU driver.
> */
> if (!group->default_domain) {
> - group->default_domain =
> - __iommu_domain_alloc(dev->bus, iommu_def_domain_type);
> + struct iommu_domain *dom;
> +
> + dom = __iommu_domain_alloc(dev->bus, iommu_def_domain_type);
> + if (!dom) {
> + dev_warn(dev,
> + "failed to allocate default IOMMU domain of
> type %u; falling back to IOMMU_DOMAIN_DMA",
> + iommu_def_domain_type);
Conversely, that's going to be noisy if iommu_def_domain_type was
IOMMU_DOMAIN_DMA to begin with. I think it makes sense to warn if the
user asked for a specific default domain type on the command line and
that didn't work, but maybe not to bother otherwise. Plus, if they asked
for passthrough, then not allocating a default domain at all is probably
closer to the desired result than installing a DMA ops domain would be.
Robin.
> + dom = __iommu_domain_alloc(dev->bus, IOMMU_DOMAIN_DMA);
> + }
> +
> + group->default_domain = dom;
> if (!group->domain)
> - group->domain = group->default_domain;
> + group->domain = dom;
> }
>
> ret = iommu_group_add_device(group, dev);
>
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