xen/arm: Introduce xen, passthrough property

When a device is marked for passthrough (via the new property
"xen,passthrough"), dom0 must not access to the device (i.e not
loading a driver), but should be able to manage the MMIO/interrupt
of the passthrough device.

The latter part will allow the toolstack to map MMIO/IRQ when a device
is pass through to a guest.

The property "xen,passthrough" will be translated as 'status="disabled"'
in the device tree to avoid DOM0 using the device. We assume that DOM0 is
able to cope with this property (already the case for Linux, and
required by ePAPR).

Rework the function map_device (renamed into handle_device) to:

* For a given device node:
    - Give permission to manage IRQ/MMIO for this device
    - Retrieve the IRQ configuration (i.e edge/level) from the device
    tree
* When the device is not marked for guest passthrough:
    - Assign the device to the guest if it's protected by an IOMMU
    - Map the IRQs and MMIOs regions to the guest

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

diff --git a/docs/misc/arm/device-tree/passthrough.txt b/docs/misc/arm/device-tree/passthrough.txt
new file mode 100644 (file)
index 0000000..6715646
--- /dev/null
+++ b/docs/misc/arm/device-tree/passthrough.txt
@@ -0,0 +1,9 @@
+Device passthrough
+===================
+
+Any device with the property "xen,passthrough" set will not be exposed to
+DOM0 and therefore no driver will be loaded.
+
+It is highly recommended to set this property on devices which are passed
+through since many devices will not cope with being accessed by dom0 and
+then handed over to another domain.

diff --git a/xen/arch/arm/device.c b/xen/arch/arm/device.c
index 675784cd9cfc19c093747697d859f3e403de6524..0b53f6a808bfaea7cfcd6f963be4259605abde88 100644 (file)
--- a/xen/arch/arm/device.c
+++ b/xen/arch/arm/device.c
@@ -30,7 +30,7 @@ int __init device_init(struct dt_device_node *dev, enum device_class class,
 
     ASSERT(dev != NULL);
 
-    if ( !dt_device_is_available(dev) )
+    if ( !dt_device_is_available(dev) || dt_device_for_passthrough(dev) )
         return  -ENODEV;
 
     for ( desc = _sdevice; desc != _edevice; desc++ )

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 31b32df345e444449d962c2f7795d90ac58dcc0b..2eb31ad5248ab61b6471c78986f713e4829d8c78 100644 (file)
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -402,7 +402,7 @@ static int write_properties(struct domain *d, struct kernel_info *kinfo,
                             const struct dt_device_node *node)
 {
     const char *bootargs = NULL;
-    const struct dt_property *prop;
+    const struct dt_property *prop, *status = NULL;
     int res = 0;
     int had_dom0_bootargs = 0;
 
@@ -457,6 +457,17 @@ static int write_properties(struct domain *d, struct kernel_info *kinfo,
             }
         }
 
+        /* Don't expose the property "xen,passthrough" to the guest */
+        if ( dt_property_name_is_equal(prop, "xen,passthrough") )
+            continue;
+
+        /* Remember and skip the status property as Xen may modify it later */
+        if ( dt_property_name_is_equal(prop, "status") )
+        {
+            status = prop;
+            continue;
+        }
+
         res = fdt_property(kinfo->fdt, prop->name, prop_data, prop_len);
 
         xfree(new_data);
@@ -465,6 +476,19 @@ static int write_properties(struct domain *d, struct kernel_info *kinfo,
             return res;
     }
 
+    /*
+     * Override the property "status" to disable the device when it's
+     * marked for passthrough.
+     */
+    if ( dt_device_for_passthrough(node) )
+        res = fdt_property_string(kinfo->fdt, "status", "disabled");
+    else if ( status )
+        res = fdt_property(kinfo->fdt, "status", status->value,
+                           status->length);
+
+    if ( res )
+        return res;
+
     if ( dt_node_path_is_equal(node, "/chosen") )
     {
         const struct bootmodule *mod = kinfo->initrd_bootmodule;
@@ -903,8 +927,15 @@ static int make_timer_node(const struct domain *d, void *fdt,
     return res;
 }
 
-/* Map the device in the domain */
-static int map_device(struct domain *d, struct dt_device_node *dev)
+/*
+ * For a given device node:
+ *  - 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:
+ *  - Assign the device to the guest if it's protected by an IOMMU
+ *  - Map the IRQs and iomem regions to DOM0
+ */
+static int handle_device(struct domain *d, struct dt_device_node *dev)
 {
     unsigned int nirq;
     unsigned int naddr;
@@ -913,13 +944,15 @@ static int map_device(struct domain *d, struct dt_device_node *dev)
     unsigned int irq;
     struct dt_raw_irq rirq;
     u64 addr, size;
+    bool_t need_mapping = !dt_device_for_passthrough(dev);
 
     nirq = dt_number_of_irq(dev);
     naddr = dt_number_of_address(dev);
 
-    DPRINT("%s nirq = %d naddr = %u\n", dt_node_full_name(dev), nirq, naddr);
+    DPRINT("%s passthrough = %d nirq = %d naddr = %u\n", dt_node_full_name(dev),
+           need_mapping, nirq, naddr);
 
-    if ( dt_device_is_protected(dev) )
+    if ( dt_device_is_protected(dev) && need_mapping )
     {
         DPRINT("%s setup iommu\n", dt_node_full_name(dev));
         res = iommu_assign_dt_device(d, dev);
@@ -931,7 +964,7 @@ static int map_device(struct domain *d, struct dt_device_node *dev)
         }
     }
 
-    /* Map IRQs */
+    /* Give permission and map IRQs */
     for ( i = 0; i < nirq; i++ )
     {
         res = dt_device_get_raw_irq(dev, i, &rirq);
@@ -970,16 +1003,34 @@ static int map_device(struct domain *d, struct dt_device_node *dev)
          * the IRQ twice. This can legitimately happen if the IRQ is shared
          */
         vgic_reserve_virq(d, irq);
-        res = route_irq_to_guest(d, irq, dt_node_name(dev));
+
+        res = irq_permit_access(d, irq);
         if ( res )
         {
-            printk(XENLOG_ERR "Unable to route IRQ %u to domain %u\n",
-                   irq, d->domain_id);
+            printk(XENLOG_ERR "Unable to permit to dom%u access to IRQ %u\n",
+                   d->domain_id, irq);
             return res;
         }
+
+        if ( need_mapping )
+        {
+            /*
+             * Checking the return of vgic_reserve_virq is not
+             * necessary. It should not fail except when we try to map
+             * twice the IRQ. This can happen if the IRQ is shared
+             */
+            vgic_reserve_virq(d, irq);
+            res = route_irq_to_guest(d, irq, dt_node_name(dev));
+            if ( res )
+            {
+                printk(XENLOG_ERR "Unable to route IRQ %u to domain %u\n",
+                       irq, d->domain_id);
+                return res;
+            }
+        }
     }
 
-    /* Map the address ranges */
+    /* Give permission and map MMIOs */
     for ( i = 0; i < naddr; i++ )
     {
         res = dt_device_get_address(dev, i, &addr, &size);
@@ -1003,17 +1054,21 @@ static int map_device(struct domain *d, struct dt_device_node *dev)
                    addr & PAGE_MASK, PAGE_ALIGN(addr + size) - 1);
             return res;
         }
-        res = map_mmio_regions(d,
-                               paddr_to_pfn(addr & PAGE_MASK),
-                               DIV_ROUND_UP(size, PAGE_SIZE),
-                               paddr_to_pfn(addr & PAGE_MASK));
-        if ( res )
+
+        if ( need_mapping )
         {
-            printk(XENLOG_ERR "Unable to map 0x%"PRIx64
-                   " - 0x%"PRIx64" in domain %d\n",
-                   addr & PAGE_MASK, PAGE_ALIGN(addr + size) - 1,
-                   d->domain_id);
-            return res;
+            res = map_mmio_regions(d,
+                                   paddr_to_pfn(addr & PAGE_MASK),
+                                   DIV_ROUND_UP(size, PAGE_SIZE),
+                                   paddr_to_pfn(addr & PAGE_MASK));
+            if ( res )
+            {
+                printk(XENLOG_ERR "Unable to map 0x%"PRIx64
+                       " - 0x%"PRIx64" in domain %d\n",
+                       addr & PAGE_MASK, PAGE_ALIGN(addr + size) - 1,
+                       d->domain_id);
+                return res;
+            }
         }
     }
 
@@ -1085,7 +1140,7 @@ static int handle_node(struct domain *d, struct kernel_info *kinfo,
         return 0;
     }
 
-    res = map_device(d, node);
+    res = handle_device(d, node);
     if ( res)
         return res;
 

diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
index 25880e8c42e9753a7d4f049efe6d492fb8deaad1..02cae911c7aa5e3a2f92763a0521270ece4716fd 100644 (file)
--- a/xen/common/device_tree.c
+++ b/xen/common/device_tree.c
@@ -1104,6 +1104,12 @@ bool_t dt_device_is_available(const struct dt_device_node *device)
     return 0;
 }
 
+bool_t dt_device_for_passthrough(const struct dt_device_node *device)
+{
+    return (dt_find_property(device, "xen,passthrough", NULL) != NULL);
+
+}
+
 static int __dt_parse_phandle_with_args(const struct dt_device_node *np,
                                         const char *list_name,
                                         const char *cells_name,

diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
index 6bbee6d412c56c51034579a6f678d0fd9ce79cd3..57eb3eea53a9399d5b5ca05d60f5dcdce6eb4af3 100644 (file)
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -555,6 +555,17 @@ int dt_n_addr_cells(const struct dt_device_node *np);
  */
 bool_t dt_device_is_available(const struct dt_device_node *device);
 
+/**
+ * dt_device_for_passthrough - Check if a device will be used for
+ * passthrough later
+ *
+ * @device: Node to check
+ *
+ * Return true if the property "xen,passthrough" is present in the node,
+ * false otherwise.
+ */
+bool_t dt_device_for_passthrough(const struct dt_device_node *device);
+
 /**
  * dt_match_node - Tell if a device_node has a matching of dt_device_match
  * @matches: array of dt_device_match structures to search in