Re: [PATCH] iommu/dma: Handle MSI mappings separately

[Andre Przywara <andre.przywara@arm.com>]

On Mon, 29 Jul 2019 16:32:38 +0100
Robin Murphy <robin.murphy@arm.com> wrote:

Hi,

> MSI pages must always be mapped into a device's *current* domain, which
> *might* be the default DMA domain, but might instead be a VFIO domain
> with its own MSI cookie. This subtlety got accidentally lost in the
> streamlining of __iommu_dma_map(), but rather than reintroduce more
> complexity and/or special-casing, it turns out neater to just split this
> path out entirely.
> 
> Since iommu_dma_get_msi_page() already duplicates much of what
> __iommu_dma_map() does, it can easily just make the allocation and
> mapping calls directly as well. That way we can further streamline the
> helper back to exclusively operating on DMA domains.
> 
> Fixes: b61d271e59d7 ("iommu/dma: Move domain lookup into __iommu_dma_{map,unmap}")
> Reported-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> Reported-by: Andre Przywara <andre.przywara@arm.com>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>

Thanks, that indeed fixes the pass through problem for me, the NVMe and SATA controller can now happily receive MSIs again.

Tested-by: Andre Przywara <andre.przywara@arm.com>

Cheers,
Andre.

> ---
>  drivers/iommu/dma-iommu.c | 17 ++++++++++-------
>  1 file changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index a7f9c3edbcb2..6441197a75ea 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -459,13 +459,11 @@ static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys,
>  {
>  	struct iommu_domain *domain = iommu_get_dma_domain(dev);
>  	struct iommu_dma_cookie *cookie = domain->iova_cookie;
> -	size_t iova_off = 0;
> +	struct iova_domain *iovad = &cookie->iovad;
> +	size_t iova_off = iova_offset(iovad, phys);
>  	dma_addr_t iova;
>  
> -	if (cookie->type == IOMMU_DMA_IOVA_COOKIE) {
> -		iova_off = iova_offset(&cookie->iovad, phys);
> -		size = iova_align(&cookie->iovad, size + iova_off);
> -	}
> +	size = iova_align(iovad, size + iova_off);
>  
>  	iova = iommu_dma_alloc_iova(domain, size, dma_get_mask(dev), dev);
>  	if (!iova)
> @@ -1147,16 +1145,21 @@ static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev,
>  	if (!msi_page)
>  		return NULL;
>  
> -	iova = __iommu_dma_map(dev, msi_addr, size, prot);
> -	if (iova == DMA_MAPPING_ERROR)
> +	iova = iommu_dma_alloc_iova(domain, size, dma_get_mask(dev), dev);
> +	if (!iova)
>  		goto out_free_page;
>  
> +	if (iommu_map(domain, iova, msi_addr, size, prot))
> +		goto out_free_iova;
> +
>  	INIT_LIST_HEAD(&msi_page->list);
>  	msi_page->phys = msi_addr;
>  	msi_page->iova = iova;
>  	list_add(&msi_page->list, &cookie->msi_page_list);
>  	return msi_page;
>  
> +out_free_iova:
> +	iommu_dma_free_iova(cookie, iova, size);
>  out_free_page:
>  	kfree(msi_page);
>  	return NULL;

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