[Xen-devel] [PATCH v9 8/8] xen/arm: add dom0-less device assignment info to docs

[Stefano Stabellini <sstabellini@kernel.org>]

Add info about the SPI used for the virtual pl011.

Signed-off-by: Stefano Stabellini <stefanos@xilinx.com>

---
Changes in v9:
- clarify statement

Changes in v8:
- remove sentence about xen,path being optional

Changes in v7:
- add xen,force-assign-without-iommu
- clarify xen,reg and xen,path go together
- remove acked-by due to changes

Changes in v6:
- fix nr_spis description
- add ack

Changes in v5:
- improve wording

Changes in v4:
- fix spelling
- add "multiboot,module"
- improve commit message
- improve doc
- expand the nr_spis and vpl011 sections and include information about
  the vpl011 SPI
- move passthrough information to docs/misc/arm/passthrough.txt

Changes in v3:
- add nr_spis
- change description of interrupts and interrupt-parent

Changes in v2:
- device tree fragment loaded in cacheable memory
- rename multiboot,dtb to multiboot,device-tree
- rename "path" to "xen,path"
- add a note about device memory mapping
- introduce xen,reg
- specify only the GIC is supported
---
 docs/misc/arm/device-tree/booting.txt |  44 ++++++++++-
 docs/misc/arm/passthrough.txt         | 106 ++++++++++++++++++++++++++
 2 files changed, 149 insertions(+), 1 deletion(-)

diff --git a/docs/misc/arm/device-tree/booting.txt b/docs/misc/arm/device-tree/booting.txt
index 317a9e962a..649e00d09f 100644
--- a/docs/misc/arm/device-tree/booting.txt
+++ b/docs/misc/arm/device-tree/booting.txt
@@ -146,7 +146,18 @@ with the following properties:
 
 - vpl011
 
-    An empty property to enable/disable a virtual pl011 for the guest to use.
+    An empty property to enable/disable a virtual pl011 for the guest to
+    use. The virtual pl011 uses SPI number 0 (see GUEST_VPL011_SPI).
+    Please note that the SPI used for the virtual pl011 could clash with the
+    physical SPI of a physical device assigned to the guest.
+
+- nr_spis
+
+    Optional. A 32-bit integer specifying the number of SPIs (Shared
+    Peripheral Interrupts) to allocate for the domain. If nr_spis is
+    missing, the max number of SPIs supported by the physical GIC is
+    used, or GUEST_VPL011_SPI+1 if vpl011 is enabled, whichever is
+    greater.
 
 - #address-cells and #size-cells
 
@@ -226,3 +237,34 @@ chosen {
         };
     };
 };
+
+
+Device Assignment
+=================
+
+Device Assignment (Passthrough) is supported by adding another module,
+alongside the kernel and ramdisk, with the device tree fragment
+corresponding to the device node to assign to the guest.
+
+The dtb sub-node should have the following properties:
+
+- compatible
+
+    "multiboot,device-tree" and "multiboot,module"
+
+- reg
+
+    Specifies the physical address of the device tree binary fragment
+    RAM and its length.
+
+As an example:
+
+        module@0xc000000 {
+            compatible = "multiboot,device-tree", "multiboot,module";
+            reg = <0x0 0xc000000 0xffffff>;
+        };
+
+The DTB fragment is loaded at 0xc000000 in the example above. It should
+follow the convention explained in docs/misc/arm/passthrough.txt. The
+DTB fragment will be added to the guest device tree, so that the guest
+kernel will be able to discover the device.
diff --git a/docs/misc/arm/passthrough.txt b/docs/misc/arm/passthrough.txt
index 0efbd122de..c85e657bca 100644
--- a/docs/misc/arm/passthrough.txt
+++ b/docs/misc/arm/passthrough.txt
@@ -80,6 +80,112 @@ SPI numbers start from 32, in this example 80 + 32 = 112.
 See man [xl.cfg] for the iomem format. The reg property is just a pair
 of address, then size numbers, each of them can occupy 1 or 2 cells.
 
+
+Dom0-less Device Passthrough
+============================
+
+The partial device tree for dom0-less guests should have the following
+properties for each node corresponding to a physical device to assign to
+the guest:
+
+- xen,reg
+
+  The xen,reg property is an array of:
+
+    <phys_addr size guest_addr>
+
+  They specify the physical address and size of the device memory
+  ranges together with the corresponding guest address to map them to.
+  The size of `phys_addr' and `guest_addr' is determined by
+  #address-cells, the size of `size' is determined by #size-cells, of
+  the partial device tree.
+  The memory will be mapped as device memory in the guest (Device-nGnRE).
+
+- xen,path
+
+  A string property representing the path in the host device tree to the
+  corresponding device node.
+
+- xen,force-assign-without-iommu
+  If xen,force-assign-without-iommu is present, Xen allows to assign a
+  device even if it is not behind an IOMMU. This renders your platform
+  *unsafe* if the device is DMA-capable.
+
+In addition, a special /gic node is expected as a placeholder for the
+full GIC node that will be added by Xen for the guest. /gic can be
+referenced by other properties in the device tree fragment. For
+instance, it can be referenced by interrupt-parent under a device node.
+Xen will take care of replacing the "gic" placeholder node for a
+complete GIC node while retaining all the references correctly. The new
+GIC node created by Xen is a regular interrupt-controller@<unit> node.
+
+    gic: gic {
+        #interrupt-cells = <0x3>;
+        interrupt-controller;
+    };
+
+Note that the #interrupt-cells and interrupt-controller properties are
+not actually required, however, DTC expects them to be present if gic is
+referenced by interrupt-parent or similar.
+
+
+Example
+=======
+
+The following is a real-world example of a device tree fragment to
+assign a network card to a dom0-less guest on Xilinx Ultrascale+ MPSoC:
+
+/dts-v1/;
+
+/ {
+    #address-cells = <2>;
+    #size-cells = <1>;
+
+    gic: gic {
+        #interrupt-cells = <3>;
+        interrupt-controller;
+    };
+
+    passthrough {
+        compatible = "simple-bus";
+        ranges;
+        #address-cells = <2>;
+        #size-cells = <1>;
+
+        misc_clk: misc_clk {
+            #clock-cells = <0>;
+            clock-frequency = <0x7735940>;
+            compatible = "fixed-clock";
+        };
+
+        ethernet@ff0e0000 {
+            compatible = "cdns,zynqmp-gem";
+            status = "okay";
+            reg = <0x0 0xff0e0000 0x1000>;
+            clock-names = "pclk", "hclk", "tx_clk", "rx_clk";
+            #address-cells = <1>;
+            #size-cells = <0>;
+            clocks = <&misc_clk &misc_clk &misc_clk &misc_clk>;
+            phy-mode = "rgmii-id";
+            xlnx,ptp-enet-clock = <0>;
+            local-mac-address = [00 0a 35 00 22 01];
+            interrupt-parent = <&gic>;
+            interrupts = <0 63 0x4 0 63 0x4>;
+            xen,path = "/amba/ethernet@ff0e0000";
+            xen,reg = <0x0 0xff0e0000 0x1000 0x0 0xff0e0000>;
+
+            phy@c {
+                reg = <0xc>;
+                ti,rx-internal-delay = <0x8>;
+                ti,tx-internal-delay = <0xa>;
+                ti,fifo-depth = <0x1>;
+                ti,rxctrl-strap-worka;
+            };
+        };
+    };
+};
+
+
 [arm,gic.txt]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/interrupt-controller/arm,gic.txt
 [arm,gic-v3.txt]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt
 [xl.cfg]: https://xenbits.xen.org/docs/unstable/man/xl.cfg.5.html
-- 
2.17.1


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