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Re: [Xen-devel] [PATCH V4 7/8] iommu/arm: Introduce iommu_add_dt_device API
Hi Oleksandr,
On 13/09/2019 16:35, Oleksandr Tyshchenko wrote:
From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
The main puprose of this patch is to add a way to register DT device
(which is behind the IOMMU) using the generic IOMMU DT bindings [1]
before assigning that device to a domain.
So, this patch adds new "iommu_add_dt_device" API for adding DT device
to the IOMMU using generic IOMMU DT bindings and previously added
"iommu_fwspec" support. It is called when constructing Dom0 since
"iommu_assign_dt_device" can be called for Dom0 also.
The last sentence is misleading. Yes some devices may be assigned to the
hardware domain (aka dom0) but other may be assigned to other domains.
Here you are (ab)using the construction of the hardware domain to add all the
devices to the IOMMU. This works fine now because the hardware domain will
always be the first domain to be initialized. But I am not sure that whether
this is correct to do long term.
As mentioned earlier, my preference is to keep "add" and "assign" separated. So
maybe what we want to do is:
if ( need_mapping )
{
iommu_add_dt_device(d, dev);
if ( dt_device_is_protected(d) )
{
res = iommu_assign_dt_device(...);
if ( res )
/* error */
}
}
We would need similar code in iommu_do_dt_domctl. Although, device should alway
be protected in this case.
Besides that, this patch adds new "dt_xlate" callback (borrowed from
Linux "of_xlate") for providing the driver with DT IOMMU specifier
which describes the IOMMU master interfaces of that device (device IDs, etc).
According to the generic IOMMU DT bindings the context of required
properties for IOMMU device/master node (#iommu-cells, iommus) depends
on many factors and is really driver depended thing.
Please note, all IOMMU drivers which support generic IOMMU DT bindings
should use "dt_xlate" and "add_device" callbacks.
[1] https://www.kernel.org/doc/Documentation/devicetree/bindings/iommu/iommu.txt
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>
CC: Jan Beulich <jbeulich@xxxxxxxx>
---
Changes V3 -> V4:
- squashed with "iommu: Add of_xlate callback" patch
- renamed "of_xlate" to "dt_xlate"
- reworked patch description
- clarified comments in code, removed confusing word
"initialize device", etc
- updated debug message in handle_device()
- modified to check ops->of_xlate and ops->add_device
only if "iommus" property is exists
Changes V2 -> V3:
- clarified patch description
- clarified comments in code
- modified to provide DT IOMMU specifier to the driver
using "of_xlate" callback
- documented function usage
- modified to return an error if ops is not present/implemented,
- added ability to return a possitive value to indicate
that device doesn't need to be protected
- removed check for the "iommu" property presence
in the common code
- included <asm/iommu_fwspec.h> directly
---
xen/arch/arm/domain_build.c | 12 +++++++
xen/drivers/passthrough/arm/iommu.c | 63 +++++++++++++++++++++++++++++++++++++
xen/include/asm-arm/iommu.h | 11 +++++++
xen/include/xen/iommu.h | 10 ++++++
4 files changed, 96 insertions(+)
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index a0fee1e..0d79182 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -1240,6 +1240,7 @@ static int __init map_device_children(struct domain *d,
/*
* For a given device node:
+ * - Try to call iommu_add_dt_device to protect the device by an IOMMU
* - Give permission to the guest to manage IRQ and MMIO range
* - Retrieve the IRQ configuration (i.e edge/level) from device tree
* When the device is not marked for guest passthrough:
@@ -1257,6 +1258,17 @@ static int __init handle_device(struct domain *d, struct
dt_device_node *dev,
u64 addr, size;
bool need_mapping = !dt_device_for_passthrough(dev);
+ dt_dprintk("Check if %s is behind the IOMMU and add it\n",
+ dt_node_full_name(dev));
+
+ res = iommu_add_dt_device(dev);
+ if ( res < 0 )
+ {
+ printk(XENLOG_ERR "Failed to add %s to the IOMMU\n",
+ dt_node_full_name(dev));
+ return res;
+ }
+
nirq = dt_number_of_irq(dev);
naddr = dt_number_of_address(dev);
diff --git a/xen/drivers/passthrough/arm/iommu.c b/xen/drivers/passthrough/arm/iommu.c
index 5a3d1d5..dea79ed 100644
--- a/xen/drivers/passthrough/arm/iommu.c
+++ b/xen/drivers/passthrough/arm/iommu.c
@@ -20,6 +20,7 @@
#include <xen/lib.h>
#include <asm/device.h>
+#include <asm/iommu_fwspec.h>
/*
* Deferred probe list is used to keep track of devices for which driver
@@ -141,3 +142,65 @@ int arch_iommu_populate_page_table(struct domain *d)
void __hwdom_init arch_iommu_hwdom_init(struct domain *d)
{
}
+
+int __init iommu_add_dt_device(struct dt_device_node *np)
Sorry to only realise it now. Would it make sense to have this function
implemented in xen/passthrough/device_tree.c? This would allow to keep
arm/iommu.c as firmware agnostic as possible.
+{
+ const struct iommu_ops *ops = iommu_get_ops();
+ struct dt_phandle_args iommu_spec;
+ struct device *dev = dt_to_dev(np);
+ int rc = 1, index = 0;
+
+ if ( !iommu_enabled )
+ return 1;
+
+ if ( !ops )
+ return -EINVAL;
+
+ if ( dev_iommu_fwspec_get(dev) )
+ return -EEXIST;
+
+ /*
+ * According to the Documentation/devicetree/bindings/iommu/iommu.txt
+ * from Linux.
+ */
+ while ( !dt_parse_phandle_with_args(np, "iommus", "#iommu-cells",
+ index, &iommu_spec) )
+ {
+ /*
+ * The driver which supports generic IOMMU DT bindings must have
+ * these callback implemented.
+ */
+ if ( !ops->add_device || !ops->dt_xlate )
+ return -EINVAL;
+
+ if ( !dt_device_is_available(iommu_spec.np) )
+ break;
+
+ rc = iommu_fwspec_init(dev, &iommu_spec.np->dev);
+ if ( rc )
+ break;
+
+ /*
+ * Provide DT IOMMU specifier which describes the IOMMU master
+ * interfaces of that device (device IDs, etc) to the driver.
+ * The driver is responsible to decide how to interpret them.
+ */
+ rc = ops->dt_xlate(dev, &iommu_spec);
+ if ( rc )
+ break;
+
+ index++;
+ }
+
+ /*
+ * Add master device to the IOMMU if latter is present and available.
+ * The driver is responsible to mark that device as protected.
+ */
+ if ( !rc )
+ rc = ops->add_device(0, dev);
+
+ if ( rc < 0 )
+ iommu_fwspec_free(dev);
+
+ return rc;
+}
diff --git a/xen/include/asm-arm/iommu.h b/xen/include/asm-arm/iommu.h
index 11dedba..04f21a2 100644
--- a/xen/include/asm-arm/iommu.h
+++ b/xen/include/asm-arm/iommu.h
@@ -27,6 +27,17 @@ const struct iommu_ops *iommu_get_ops(void);
void iommu_set_ops(const struct iommu_ops *ops);
/*
+ * Helper to add master device to the IOMMU using generic IOMMU DT bindings.
+ *
+ * Return values:
+ * 0 : device is protected by an IOMMU
+ * <0 : device is not protected by an IOMMU, but must be (error condition)
+ * >0 : device doesn't need to be protected by an IOMMU
+ * (IOMMU is not enabled/present or device is not connected to it).
+ */
+int iommu_add_dt_device(struct dt_device_node *np);
+
+/*
* The mapping helpers below should only be used if P2M Table is shared
* between the CPU and the IOMMU.
*/
diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
index ab258b8..59a2cee 100644
--- a/xen/include/xen/iommu.h
+++ b/xen/include/xen/iommu.h
@@ -239,6 +239,16 @@ struct iommu_ops {
int __must_check (*iotlb_flush_all)(struct domain *d);
int (*get_reserved_device_memory)(iommu_grdm_t *, void *);
void (*dump_p2m_table)(struct domain *d);
+
+#ifdef CONFIG_HAS_DEVICE_TREE
+ /*
+ * All IOMMU drivers which support generic IOMMU DT bindings should use
+ * this callback. This is a way for the framework to provide the driver
+ * with DT IOMMU specifier which describes the IOMMU master interfaces of
+ * that device (device IDs, etc).
+ */
+ int (*dt_xlate)(device_t *dev, struct dt_phandle_args *args);
+#endif
};
#include <asm/iommu.h>
Cheers,
--
Julien Grall
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