Re: [PATCH v13 03/15] iommu/dma: Allow MSI-only cookies

Alex Williamson
2016-10-06T20:17:28Z

On Thu, 6 Oct 2016 08:45:19 +0000
Eric Auger <eric.auger@redhat.com> wrote:

> From: Robin Murphy <robin.murphy@arm.com>
>
> IOMMU domain users such as VFIO face a similar problem to DMA API ops
> with regard to mapping MSI messages in systems where the MSI write is
> subject to IOMMU translation. With the relevant infrastructure now in
> place for managed DMA domains, it's actually really simple for other
> users to piggyback off that and reap the benefits without giving up
> their own IOVA management, and without having to reinvent their own
> wheel in the MSI layer.
>
> Allow such users to opt into automatic MSI remapping by dedicating a
> region of their IOVA space to a managed cookie.
>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>
> ---
>
> v1 -> v2:
> - compared to Robin's version
> - add NULL last param to iommu_dma_init_domain
> - set the msi_geometry aperture
> - I removed
> if (base < U64_MAX - size)
> reserve_iova(iovad, iova_pfn(iovad, base + size), ULONG_MAX);
> don't get why we would reserve something out of the scope of the iova domain?
> what do I miss?
> ---
> drivers/iommu/dma-iommu.c | 40 ++++++++++++++++++++++++++++++++++++++++
> include/linux/dma-iommu.h | 9 +++++++++
> 2 files changed, 49 insertions(+)
>
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index c5ab866..11da1a0 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -716,3 +716,43 @@ void iommu_dma_map_msi_msg(int irq, struct msi_msg *msg)
> msg->address_lo += lower_32_bits(msi_page->iova);
> }
> }
> +
> +/**
> + * iommu_get_dma_msi_region_cookie - Configure a domain for MSI remapping only

Should this perhaps be iommu_setup_dma_msi_region_cookie, or something
along those lines. I'm not sure what we're get'ing. Thanks,

Alex

> + * @domain: IOMMU domain to prepare
> + * @base: Base address of IOVA region to use as the MSI remapping aperture
> + * @size: Size of the desired MSI aperture
> + *
> + * Users who manage their own IOVA allocation and do not want DMA API support,
> + * but would still like to take advantage of automatic MSI remapping, can use
> + * this to initialise their own domain appropriately.
> + */
> +int iommu_get_dma_msi_region_cookie(struct iommu_domain *domain,
> + dma_addr_t base, u64 size)
> +{
> + struct iommu_dma_cookie *cookie;
> + struct iova_domain *iovad;
> + int ret;
> +
> + if (domain->type == IOMMU_DOMAIN_DMA)
> + return -EINVAL;
> +
> + ret = iommu_get_dma_cookie(domain);
> + if (ret)
> + return ret;
> +
> + ret = iommu_dma_init_domain(domain, base, size, NULL);
> + if (ret) {
> + iommu_put_dma_cookie(domain);
> + return ret;
> + }
> +
> + domain->msi_geometry.aperture_start = base;
> + domain->msi_geometry.aperture_end = base + size - 1;
> +
> + cookie = domain->iova_cookie;
> + iovad = &cookie->iovad;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(iommu_get_dma_msi_region_cookie);
> diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h
> index 32c5890..1c55413 100644
> --- a/include/linux/dma-iommu.h
> +++ b/include/linux/dma-iommu.h
> @@ -67,6 +67,9 @@ int iommu_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
> /* The DMA API isn't _quite_ the whole story, though... */
> void iommu_dma_map_msi_msg(int irq, struct msi_msg *msg);
>
> +int iommu_get_dma_msi_region_cookie(struct iommu_domain *domain,
> + dma_addr_t base, u64 size);
> +
> #else
>
> struct iommu_domain;
> @@ -90,6 +93,12 @@ static inline void iommu_dma_map_msi_msg(int irq, struct msi_msg *msg)
> {
> }
>
> +static inline int iommu_get_dma_msi_region_cookie(struct iommu_domain *domain,
> + dma_addr_t base, u64 size)
> +{
> + return -ENODEV;
> +}
> +
> #endif /* CONFIG_IOMMU_DMA */
> #endif /* __KERNEL__ */
> #endif /* __DMA_IOMMU_H */