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Re: [Xen-devel] [PATCH v7b 5/8] xen/arm: assign devices to boot domains



Hi Stefano,

On 10/1/19 12:30 AM, Stefano Stabellini wrote:
Scan the user provided dtb fragment at boot. For each device node, map
memory to guests, and route interrupts and setup the iommu.

The memory region to remap is specified by the "xen,reg" property.

The iommu is setup by passing the node of the device to assign on the
host device tree. The path is specified in the device tree fragment as
the "xen,path" string property.

The interrupts are remapped based on the information from the
corresponding node on the host device tree. Call
handle_device_interrupts to remap interrupts. Interrupts related device
tree properties are copied from the device tree fragment, same as all
the other properties.

Require both xen,reg and xen,path to be present, unless
xen,force-assign-without-iommu is also set. In that case, tolerate a
missing xen,path, also tolerate iommu setup failure for the passthrough
device.

Also set add the new flag XEN_DOMCTL_CDF_iommu so that dom0less domU
can use the IOMMU if a partial dtb is specified.

The patch looks good a few comments below.

[...]

  xen/arch/arm/domain_build.c | 133 ++++++++++++++++++++++++++++++++++--
  1 file changed, 129 insertions(+), 4 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 84b65b8f25..47f9bb31df 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -1714,6 +1714,88 @@ static int __init make_vpl011_uart_node(struct 
kernel_info *kinfo)
  }
  #endif
+/*
+ * Scan device tree properties for passthrough specific information.
+ * Returns < 0 on error
+ *         0 on success
+ */
+static int __init handle_passthrough_prop(struct kernel_info *kinfo,
+                                          const struct fdt_property *xen_reg,
+                                          const struct fdt_property *xen_path,
+                                          bool xen_force,
+                                          uint32_t address_cells, uint32_t 
size_cells)
+{
+    const __be32 *cell;
+    unsigned int i, len;
+    struct dt_device_node *node;
+    int res;
+    paddr_t mstart, size, gstart;
+
+    /* xen,reg specifies where to map the MMIO region */
+    cell = (const __be32 *)xen_reg->data;
+    len = fdt32_to_cpu(xen_reg->len) /
+          ((address_cells * 2 + size_cells) * sizeof(uint32_t));

Coding style again. I was kind of expecting you configured your editor properly after the last discussion...

[...]

  static int __init handle_prop_pfdt(struct kernel_info *kinfo,
                                     const void *pfdt, int nodeoff,
                                     uint32_t address_cells, uint32_t 
size_cells,
@@ -1721,7 +1803,9 @@ static int __init handle_prop_pfdt(struct kernel_info 
*kinfo,
  {
      void *fdt = kinfo->fdt;
      int propoff, nameoff, res;
-    const struct fdt_property *prop;
+    const struct fdt_property *prop, *xen_reg = NULL, *xen_path = NULL;
+    const char *name;
+    bool found, xen_force = false;
for ( propoff = fdt_first_property_offset(pfdt, nodeoff);
            propoff >= 0;
@@ -1730,10 +1814,48 @@ static int __init handle_prop_pfdt(struct kernel_info 
*kinfo,
          if ( !(prop = fdt_get_property_by_offset(pfdt, propoff, NULL)) )
              return -FDT_ERR_INTERNAL;
+ found = false;
          nameoff = fdt32_to_cpu(prop->nameoff);
-        res = fdt_property(fdt, fdt_string(pfdt, nameoff),
-                           prop->data, fdt32_to_cpu(prop->len));
-        if ( res )
+        name = fdt_string(pfdt, nameoff);
+
+        if ( scan_passthrough_prop )
+        {
+            if ( dt_prop_cmp("xen,reg", name) == 0 )
+            {
+                xen_reg = prop;
+                found = true;
+            }
+            else if ( dt_prop_cmp("xen,path", name) == 0 )
+            {
+                xen_path = prop;
+                found = true;
+            }
+            else if ( dt_prop_cmp("xen,force-assign-without-iommu",
+                      name) == 0 )

Coding style.

+            {
+                xen_force = true;
+                found = true;
+            }
+        }
+
+        /* Copy all other properties */

It is not entirely clear what you mean by "other" here.

+        if ( !found )
+        {
+            res = fdt_property(fdt, name, prop->data, fdt32_to_cpu(prop->len));
+            if ( res )
+                return res;
+        }
+    }
+
+    /*
+     * Only handle passthrough properties if both xen,reg and xen,path
+     * are present, or if xen,force-assign-without-iommu is specified.
+     */
+    if ( xen_reg != NULL && (xen_path != NULL || xen_force) )
+    {
+        res = handle_passthrough_prop(kinfo, xen_reg, xen_path, xen_force,
+                                      address_cells, size_cells);
+        if ( res < 0 )
              return res;
      }

I would print an error so the user knows what happen here.

@@ -2291,6 +2413,9 @@ void __init create_domUs(void)
              panic("Missing property 'cpus' for domain %s\n",
                    dt_node_name(node));
+ if ( dt_find_compatible_node(node, NULL, "multiboot,device-tree") )
+            d_cfg.flags |= XEN_DOMCTL_CDF_iommu;
+
          d = domain_create(++max_init_domid, &d_cfg, false);
          if ( IS_ERR(d) )
              panic("Error creating domain %s\n", dt_node_name(node));


Cheers,

--
Julien Grall

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