Re: [RFC PATCH 3/4] ACPI/IORT: Add RMR memory regions reservation helper

Robin Murphy
2020-11-05T18:04:09Z

On 2020-10-27 11:26, Shameer Kolothum wrote:
> Add a helper function that retrieves RMR memory descriptors
> associated with a given endpoint dev. These memory regions
> should have a unity mapping in the SMMU. So reserve them as
> IOMMU_RESV_DIRECT.

As a general observation, we also need a way into this that isn't from
the perspective of endpoint devices. With SMMUv3 we need to know all the
active stream IDs relevant to a given SMMU instance at probe time, so
that we can set up some kind of valid stream table entries *before*
enabling the SMMU in the reset routine. Otherwise we're just going to
kill ongoing traffic (e.g. EFI GOP) with C_BAD_STE long before we ever
start adding devices and worrying about reserved regions for them.
Similarly for the initial SMR/S2CR state on SMMUv2 with disable_bypass.

Robin.

> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> ---
> drivers/acpi/arm64/iort.c | 56 +++++++++++++++++++++++++++++++++++++++
> include/linux/acpi_iort.h | 4 +++
> 2 files changed, 60 insertions(+)
>
> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> index b32cd53cca08..c0700149e60b 100644
> --- a/drivers/acpi/arm64/iort.c
> +++ b/drivers/acpi/arm64/iort.c
> @@ -842,6 +842,60 @@ static inline int iort_add_device_replay(struct device *dev)
> return err;
> }
>
> +static bool iort_dev_has_rmr(struct device *dev, struct iort_rmr_entry *e)
> +{
> + struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> + struct acpi_iort_node *iommu;
> + struct iort_rmr_id *rmr_ids = e->rmr_ids;
> + int i, j;
> +
> + iommu = iort_get_iort_node(fwspec->iommu_fwnode);
> +
> + for (i = 0; i < e->rmr_ids_num; i++, rmr_ids++) {
> + for (j = 0; j < fwspec->num_ids; j++) {
> + if (rmr_ids->sid == fwspec->ids[j] &&
> + rmr_ids->smmu == iommu)
> + return true;
> + }
> + }
> +
> + return false;
> +}
> +
> +/**
> + * iort_dev_rmr_get_resv_regions - RMR Reserved region driver helper
> + * @dev: Device from iommu_get_resv_regions()
> + * @head: Reserved region list from iommu_get_resv_regions()
> + *
> + * Returns: 0 on success, <0 failure
> + */
> +int iort_dev_rmr_get_resv_regions(struct device *dev, struct list_head *head)
> +{
> + struct iort_rmr_entry *e;
> +
> + list_for_each_entry(e, &iort_rmr_list, list) {
> + struct iommu_resv_region *region;
> + struct acpi_iort_rmr_desc *rmr;
> + int prot = IOMMU_READ | IOMMU_WRITE |
> + IOMMU_NOEXEC | IOMMU_MMIO;
> +
> + if (!iort_dev_has_rmr(dev, e))
> + continue;
> +
> + rmr = e->rmr_desc;
> + region = iommu_alloc_resv_region(rmr->base_address,
> + rmr->length, prot,
> + IOMMU_RESV_DIRECT);
> + if (!region) {
> + dev_err(dev, "Out of memory allocating RMR regions\n");
> + return -ENOMEM;
> + }
> + list_add_tail(&region->list, head);
> + }
> +
> + return 0;
> +}
> +
> /**
> * iort_iommu_msi_get_resv_regions - Reserved region driver helper
> * @dev: Device from iommu_get_resv_regions()
> @@ -1112,6 +1166,8 @@ int iort_iommu_msi_get_resv_regions(struct device *dev, struct list_head *head)
> const struct iommu_ops *iort_iommu_configure_id(struct device *dev,
> const u32 *input_id)
> { return NULL; }
> +int iort_dev_rmr_get_resv_regions(struct device *dev, struct list_head *head)
> +{ return 0; }
> #endif
>
> static int nc_dma_get_range(struct device *dev, u64 *size)
> diff --git a/include/linux/acpi_iort.h b/include/linux/acpi_iort.h
> index 20a32120bb88..6dd89faf340c 100644
> --- a/include/linux/acpi_iort.h
> +++ b/include/linux/acpi_iort.h
> @@ -38,6 +38,7 @@ void iort_dma_setup(struct device *dev, u64 *dma_addr, u64 *size);
> const struct iommu_ops *iort_iommu_configure_id(struct device *dev,
> const u32 *id_in);
> int iort_iommu_msi_get_resv_regions(struct device *dev, struct list_head *head);
> +int iort_dev_rmr_get_resv_regions(struct device *dev, struct list_head *head);
> #else
> static inline void acpi_iort_init(void) { }
> static inline u32 iort_msi_map_id(struct device *dev, u32 id)
> @@ -55,6 +56,9 @@ static inline const struct iommu_ops *iort_iommu_configure_id(
> static inline
> int iort_iommu_msi_get_resv_regions(struct device *dev, struct list_head *head)
> { return 0; }
> +static inline
> +int iort_dev_rmr_get_resv_regions(struct device *dev, struct list_head *head)
> +{ return 0; }
> #endif
>
> #endif /* __ACPI_IORT_H__ */
>