Re: [PATCH v5 3/8] ACPI/IORT: Add a helper to retrieve RMR memory regions

[Jon Nettleton <jon@solid-run.com>]

On Mon, Jun 14, 2021 at 2:49 PM Shameerali Kolothum Thodi
<shameerali.kolothum.thodi@huawei.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Robin Murphy [mailto:robin.murphy@arm.com]
> > Sent: 14 June 2021 12:23
> > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>;
> > linux-arm-kernel@lists.infradead.org; linux-acpi@vger.kernel.org;
> > iommu@lists.linux-foundation.org
> > Cc: jon@solid-run.com; Linuxarm <linuxarm@huawei.com>;
> > steven.price@arm.com; Guohanjun (Hanjun Guo) <guohanjun@huawei.com>;
> > yangyicong <yangyicong@huawei.com>; Sami.Mujawar@arm.com;
> > wanghuiqiang <wanghuiqiang@huawei.com>
> > Subject: Re: [PATCH v5 3/8] ACPI/IORT: Add a helper to retrieve RMR memory
> > regions
> >
> > On 2021-05-24 12:02, Shameer Kolothum wrote:
> > > Add a helper function that retrieves RMR memory descriptors
> > > associated with a given IOMMU. This will be used by IOMMU
> > > drivers to setup necessary mappings.
> > >
> > > Now that we have this, invoke it from the generic helper
> > > interface.
> > >
> > > Signed-off-by: Shameer Kolothum
> > <shameerali.kolothum.thodi@huawei.com>
> > > ---
> > >   drivers/acpi/arm64/iort.c | 50
> > +++++++++++++++++++++++++++++++++++++++
> > >   drivers/iommu/dma-iommu.c |  4 ++++
> > >   include/linux/acpi_iort.h |  7 ++++++
> > >   3 files changed, 61 insertions(+)
> > >
> > > diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> > > index fea1ffaedf3b..01917caf58de 100644
> > > --- a/drivers/acpi/arm64/iort.c
> > > +++ b/drivers/acpi/arm64/iort.c
> > > @@ -12,6 +12,7 @@
> > >
> > >   #include <linux/acpi_iort.h>
> > >   #include <linux/bitfield.h>
> > > +#include <linux/dma-iommu.h>
> > >   #include <linux/iommu.h>
> > >   #include <linux/kernel.h>
> > >   #include <linux/list.h>
> > > @@ -837,6 +838,53 @@ static inline int iort_add_device_replay(struct
> > device *dev)
> > >     return err;
> > >   }
> > >
> > > +/**
> > > + * iort_iommu_get_rmrs - Helper to retrieve RMR info associated with
> > IOMMU
> > > + * @iommu: fwnode for the IOMMU
> > > + * @head: RMR list head to be populated
> > > + *
> > > + * Returns: 0 on success, <0 failure
> > > + */
> > > +int iort_iommu_get_rmrs(struct fwnode_handle *iommu_fwnode,
> > > +                   struct list_head *head)
> > > +{
> > > +   struct iort_rmr_entry *e;
> > > +   struct acpi_iort_node *iommu;
> > > +   int rmrs = 0;
> > > +
> > > +   iommu = iort_get_iort_node(iommu_fwnode);
> > > +   if (!iommu || list_empty(&iort_rmr_list))
> > > +           return -ENODEV;
> > > +
> > > +   list_for_each_entry(e, &iort_rmr_list, list) {
> > > +           int prot = IOMMU_READ | IOMMU_WRITE | IOMMU_NOEXEC |
> > IOMMU_MMIO;
> > > +           struct iommu_resv_region *region;
> > > +           enum iommu_resv_type type;
> > > +           struct acpi_iort_rmr_desc *rmr_desc;
> > > +
> > > +           if (e->smmu != iommu)
> > > +                   continue;
> > > +
> > > +           rmr_desc = e->rmr_desc;
> > > +           if (e->flags & IOMMU_RMR_REMAP_PERMITTED)
> > > +                   type = IOMMU_RESV_DIRECT_RELAXABLE;
> > > +           else
> > > +                   type = IOMMU_RESV_DIRECT;
> >

I have been looking at this a bit more and looking at the history of
RMR_REMAP_PERMITTED.  Based on the history I have found it
seems to me like this would be the better options for prot.

@@ -840,7 +840,7 @@ int iort_iommu_get_rmrs(struct fwnode_handle *iommu_fwnode,
                return -ENODEV;

        list_for_each_entry(e, &iort_rmr_list, list) {
-               int prot = IOMMU_READ | IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
+               int prot = IOMMU_READ | IOMMU_WRITE;
                struct iommu_resv_region *region;
                enum iommu_resv_type type;
                struct acpi_iort_rmr_desc *rmr_desc;
@@ -849,10 +849,13 @@ int iort_iommu_get_rmrs(struct fwnode_handle
*iommu_fwnode,
                        continue;

                rmr_desc = e->rmr_desc;
-               if (e->flags & IOMMU_RMR_REMAP_PERMITTED)
+               if (e->flags & IOMMU_RMR_REMAP_PERMITTED) {
                        type = IOMMU_RESV_DIRECT_RELAXABLE;
-               else
+                       prot |= IOMMU_CACHE;
+               } else {
                        type = IOMMU_RESV_DIRECT;
+                       prot |= IOMMU_MMIO;
+               }

                region = iommu_alloc_resv_region(rmr_desc->base_address,
                                                 rmr_desc->length,

any input on this?  My reasoning is that IOMMU_RESV_DIRECT is specifically
referenced for things like MSI doorbell and in all the examples needs
IOMMU_MMIO, while REMAP_PERMITTED seems to be used for allocated
system memory that is then used for device specific reserved regions which
commits say would be like a GPU or USB device.

-Jon

> > Wasn't the idea that we can do all this during the initial parsing, i.e.
> > we don't even have iort_rmr_entry, we store them as iommu_resv_regions
> > and simply kmemdup() or whatever at this point?
>
>
> Hmm... Not yet. I removed struct iommu_rmr() from v4. But yes, it looks like
> we can get rid of iort_rmr_entry as well. Will give it a go in next.
>
> Thanks,
> Shameer
>
> > Robin.
> >
> > > +
> > > +           region = iommu_alloc_resv_region(rmr_desc->base_address,
> > > +                                            rmr_desc->length,
> > > +                                            prot, type);
> > > +           if (region) {
> > > +                   region->fw_data.rmr.flags = e->flags;
> > > +                   region->fw_data.rmr.sid = e->sid;
> > > +                   list_add_tail(&region->list, head);
> > > +                   rmrs++;
> > > +           }
> > > +   }
> > > +
> > > +   return (rmrs == 0) ? -ENODEV : 0;
> > > +}
> > > +
> > >   /**
> > >    * iort_iommu_msi_get_resv_regions - Reserved region driver helper
> > >    * @dev: Device from iommu_get_resv_regions()
> > > @@ -1108,6 +1156,8 @@ 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_iommu_get_rmrs(struct fwnode_handle *fwnode, struct list_head
> > *head)
> > > +{ return -ENODEV; }
> > >   #endif
> > >
> > >   static int nc_dma_get_range(struct device *dev, u64 *size)
> > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> > > index 229ec65d98be..f893d460cfa4 100644
> > > --- a/drivers/iommu/dma-iommu.c
> > > +++ b/drivers/iommu/dma-iommu.c
> > > @@ -185,6 +185,9 @@ EXPORT_SYMBOL(iommu_put_dma_cookie);
> > >   int iommu_dma_get_rmrs(struct fwnode_handle *iommu_fwnode,
> > >                    struct list_head *list)
> > >   {
> > > +   if (!is_of_node(iommu_fwnode))
> > > +           return iort_iommu_get_rmrs(iommu_fwnode, list);
> > > +
> > >     return -EINVAL;
> > >   }
> > >   EXPORT_SYMBOL(iommu_dma_get_rmrs);
> > > @@ -200,6 +203,7 @@ EXPORT_SYMBOL(iommu_dma_get_rmrs);
> > >   void iommu_dma_put_rmrs(struct fwnode_handle *iommu_fwnode,
> > >                     struct list_head *list)
> > >   {
> > > +   generic_iommu_put_resv_regions(iommu_fwnode->dev, list);
> > >   }
> > >   EXPORT_SYMBOL(iommu_dma_put_rmrs);
> > >
> > > diff --git a/include/linux/acpi_iort.h b/include/linux/acpi_iort.h
> > > index 1a12baa58e40..e8c45fa59531 100644
> > > --- a/include/linux/acpi_iort.h
> > > +++ b/include/linux/acpi_iort.h
> > > @@ -39,6 +39,8 @@ 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);
> > >   phys_addr_t acpi_iort_dma_get_max_cpu_address(void);
> > > +int iort_iommu_get_rmrs(struct fwnode_handle *iommu_fwnode,
> > > +                   struct list_head *list);
> > >   #else
> > >   static inline void acpi_iort_init(void) { }
> > >   static inline u32 iort_msi_map_id(struct device *dev, u32 id)
> > > @@ -59,6 +61,11 @@ int iort_iommu_msi_get_resv_regions(struct device
> > *dev, struct list_head *head)
> > >
> > >   static inline phys_addr_t acpi_iort_dma_get_max_cpu_address(void)
> > >   { return PHYS_ADDR_MAX; }
> > > +
> > > +static inline
> > > +int iort_iommu_get_rmrs(struct fwnode_handle *iommu_fwnode,
> > > +                   struct list_head *list)
> > > +{ return -ENODEV; }
> > >   #endif
> > >
> > >   #endif /* __ACPI_IORT_H__ */
> > >

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