Re: [PATCH v4 1/7] iommu: Move iotlb_sync_map out from __iommu_map

[Doug Anderson]

Hi,

On Thu, Jan 7, 2021 at 4:31 AM Yong Wu <yong.wu@xxxxxxxxxxxx> wrote:
>
> @@ -2438,18 +2435,31 @@ static int __iommu_map(struct iommu_domain *domain, unsigned long iova,
>         return ret;
>  }
>
> +static int _iommu_map(struct iommu_domain *domain, unsigned long iova,
> +                     phys_addr_t paddr, size_t size, int prot, gfp_t gfp)
> +{
> +       const struct iommu_ops *ops = domain->ops;
> +       int ret;
> +
> +       ret = __iommu_map(domain, iova, paddr, size, prot, GFP_KERNEL);

The above is broken.  Instead of GFP_KERNEL it should be passing "gfp".


> +       if (ret == 0 && ops->iotlb_sync_map)
> +               ops->iotlb_sync_map(domain);
> +
> +       return ret;
> +}
> +
>  int iommu_map(struct iommu_domain *domain, unsigned long iova,
>               phys_addr_t paddr, size_t size, int prot)
>  {
>         might_sleep();
> -       return __iommu_map(domain, iova, paddr, size, prot, GFP_KERNEL);
> +       return _iommu_map(domain, iova, paddr, size, prot, GFP_KERNEL);
>  }
>  EXPORT_SYMBOL_GPL(iommu_map);
>
>  int iommu_map_atomic(struct iommu_domain *domain, unsigned long iova,
>               phys_addr_t paddr, size_t size, int prot)
>  {
> -       return __iommu_map(domain, iova, paddr, size, prot, GFP_ATOMIC);
> +       return _iommu_map(domain, iova, paddr, size, prot, GFP_ATOMIC);

Specifically the above bug means we drop the "GFP_ATOMIC" here.

It means we trigger a warning, like this (on a downstream kernel with
the patch backported):

 BUG: sleeping function called from invalid context at mm/page_alloc.c:4726
 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 9, name: ksoftirqd/0
 CPU: 0 PID: 9 Comm: ksoftirqd/0 Not tainted 5.4.93-12508-gc10c93e28e39 #1
 Call trace:
  dump_backtrace+0x0/0x154
  show_stack+0x20/0x2c
  dump_stack+0xa0/0xfc
  ___might_sleep+0x11c/0x12c
  __might_sleep+0x50/0x84
  __alloc_pages_nodemask+0xf8/0x2bc
  __arm_lpae_alloc_pages+0x48/0x1b4
  __arm_lpae_map+0x124/0x274
  __arm_lpae_map+0x1cc/0x274
  arm_lpae_map+0x140/0x170
  arm_smmu_map+0x78/0xbc
  __iommu_map+0xd4/0x210
  _iommu_map+0x4c/0x84
  iommu_map_atomic+0x44/0x58
  __iommu_dma_map+0x8c/0xc4
  iommu_dma_map_page+0xac/0xf0

---

A quick (but not very tested) fix at:

https://lore.kernel.org/r/20210201170611.1.I64a7b62579287d668d7c89e105dcedf45d641063@changeid/


-Doug