> From: Nicolin Chen <nicolinc@xxxxxxxxxx>
> Sent: Saturday, August 3, 2024 8:32 AM
>
> From: Robin Murphy <robin.murphy@xxxxxxx>
>
> Currently, iommu-dma is the only place outside of IOMMUFD and drivers
> which might need to be aware of the stage 2 domain encapsulated within
> a nested domain. This would be in the legacy-VFIO-style case where we're
why is it a legacy-VFIO-style? We only support nested in IOMMUFD.
> using host-managed MSIs with an identity mapping at stage 1, where it is
> the underlying stage 2 domain which owns an MSI cookie and holds the
> corresponding dynamic mappings. Hook up the new op to resolve what we
> need from a nested domain.
>
> Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
> Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> ---
> drivers/iommu/dma-iommu.c | 18 ++++++++++++++++--
> include/linux/iommu.h | 4 ++++
> 2 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 7b1dfa0665df6..05e04934a5f81 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -1799,6 +1799,20 @@ static struct iommu_dma_msi_page
> *iommu_dma_get_msi_page(struct device *dev,
> return NULL;
> }
>
> +/*
> + * Nested domains may not have an MSI cookie or accept mappings, but
> they may
> + * be related to a domain which does, so we let them tell us what they need.
> + */
> +static struct iommu_domain
> *iommu_dma_get_msi_mapping_domain(struct device *dev)
> +{
> + struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
> +
> + if (domain && domain->type == IOMMU_DOMAIN_NESTED &&
> + domain->ops->get_msi_mapping_domain)
I'm not sure the core should restrict it to the NESTED type. Given
there is a new domain ops any type restriction can be handled
inside the callback. Anyway the driver should register the op
for a domain only when there is a need.
> + domain = domain->ops->get_msi_mapping_domain(domain);
> + return domain;
> +}
> +
> /**
> * iommu_dma_prepare_msi() - Map the MSI page in the IOMMU domain
> * @desc: MSI descriptor, will store the MSI page
> @@ -1809,7 +1823,7 @@ static struct iommu_dma_msi_page
> *iommu_dma_get_msi_page(struct device *dev,
> int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr)
> {
> struct device *dev = msi_desc_to_dev(desc);
> - struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
> + struct iommu_domain *domain =
> iommu_dma_get_msi_mapping_domain(dev);
> struct iommu_dma_msi_page *msi_page;
> static DEFINE_MUTEX(msi_prepare_lock); /* see below */
>
> @@ -1842,7 +1856,7 @@ int iommu_dma_prepare_msi(struct msi_desc
> *desc, phys_addr_t msi_addr)
> void iommu_dma_compose_msi_msg(struct msi_desc *desc, struct msi_msg
> *msg)
> {
> struct device *dev = msi_desc_to_dev(desc);
> - const struct iommu_domain *domain =
> iommu_get_domain_for_dev(dev);
> + const struct iommu_domain *domain =
> iommu_dma_get_msi_mapping_domain(dev);
> const struct iommu_dma_msi_page *msi_page;
>
> msi_page = msi_desc_get_iommu_cookie(desc);
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 4d47f2c333118..69ed76f9c3ec4 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -638,6 +638,8 @@ struct iommu_ops {
> * @enable_nesting: Enable nesting
> * @set_pgtable_quirks: Set io page table quirks (IO_PGTABLE_QUIRK_*)
> * @free: Release the domain after use.
> + * @get_msi_mapping_domain: Return the related iommu_domain that
> should hold the
> + * MSI cookie and accept mapping(s).
> */
> struct iommu_domain_ops {
> int (*attach_dev)(struct iommu_domain *domain, struct device *dev);
> @@ -668,6 +670,8 @@ struct iommu_domain_ops {
> unsigned long quirks);
>
> void (*free)(struct iommu_domain *domain);
> + struct iommu_domain *
> + (*get_msi_mapping_domain)(struct iommu_domain
> *domain);
> };
>
> /**
> --
> 2.43.0
>
