[PATCH V9 0/3] toolstack support for generic virtio devices on Arm

[PATCH V9 0/3] toolstack support for generic virtio devices on Arm

[Viresh Kumar]

Hello,

This patchset adds toolstack support for I2C, GPIO and generic virtio devices.
This is inspired from the work done by Oleksandr for the Disk device.

This is developed as part of Linaro's Project Stratos, where we are working
towards Hypervisor agnostic Rust based backends [1].

This is based of Xen's master branch.

V8->V9:
- Drop changes to tools/ocaml/libs/xl/genwrap.py file.
- Replace GPIO with I2C in a comment.
- Add Reviewed-by tags.

V7->V8:
- Use macros for compatible string names.
- Use strcmp() instead of strncmp() at several places.
- Rename "virtio,devices" to "virtio,device" in commit log.
- Remove extra call to fdt_end_node().
- Disallow "unknown" in xenstore transport.
- Use libxl__strdup().
- Update documentation.
- Remove DEVICE_ADDREMOVE(virtio).

V6->V7:
- Support generic virtio devices too. They are passed with type=virtio,device,
  and we only create the MMIO DT node for them.
- Add links to DT bindings of I2C and GPIO, in code and documentation.
- Call libxl__device_add() for all hypervisor types.
- Add (0, "UNKNOWN") for libxl_virtio_transport.
- Removed libxl_virtio_backend and libxl_virtioinfo, as they were unused.
- Remove unnecessary stuff from libxl__virtio_from_xenstore() and add support
  for type and transport.
- Add backend=domid in documentation and replace compatible with type.
- Improved commit logs.

V5->V6:
- The cleanup patches are sent separately [2].
- We don't add I2C or GPIO specific device changes anymore, rather we create
  generic "virtio" devices. The "type" of a virtio devices helps us identify the
  right device, and create an entry in the DT node. The same can be used for all
  Virtio devices now.
- Update man page xl.cfg.

V4->V5:
- Fixed indentation at few places.
- Removed/added blank lines.
- Added few comments.
- Added review tags from Oleksandr.
- Rebased over latest staging branch.

V3->V4:
- Update virtio_enabled independently of all devices, so we don't miss setting
  it to true.

- Add iommu handling for i2c/gpio and move it as part of
  make_virtio_mmio_node_common(), which gets backend_domid parameter as a
  result.

V2->V3:
- Rebased over latest tree and made changes according to changes in Oleksandr's
  patches from sometime back.
- Minor cleanups.

V1->V2:
- Patches 3/6 and 4/6 are new.
- Patches 5/6 and 6/6 updated based on the above two patches.
- Added link to the bindings for I2C and GPIO.
- Rebased over latest master branch.


Thanks.

--
Viresh

[1] https://lore.kernel.org/xen-devel/20220414092358.kepxbmnrtycz7mhe@vireshk-i7/

Viresh Kumar (3):
  libxl: Add support for generic virtio device
  xl: Add support to parse generic virtio device
  docs: Add documentation for generic virtio devices

 docs/man/xl.cfg.5.pod.in                  |  33 +++++
 tools/libs/light/Makefile                 |   1 +
 tools/libs/light/libxl_arm.c              | 100 +++++++++++++++
 tools/libs/light/libxl_create.c           |   4 +
 tools/libs/light/libxl_internal.h         |   6 +
 tools/libs/light/libxl_types.idl          |  18 +++
 tools/libs/light/libxl_types_internal.idl |   1 +
 tools/libs/light/libxl_virtio.c           | 144 ++++++++++++++++++++++
 tools/xl/xl_parse.c                       |  81 ++++++++++++
 9 files changed, 388 insertions(+)
 create mode 100644 tools/libs/light/libxl_virtio.c

-- 
2.31.1.272.g89b43f80a514

[PATCH V9 1/3] libxl: Add support for generic virtio device

[Viresh Kumar]

This patch adds basic support for configuring and assisting generic
Virtio backends, which could run in any domain.

An example of domain configuration for mmio based Virtio I2C device is:
virtio = ["type=virtio,device22,transport=mmio"]

To make this work on Arm, allocate Virtio MMIO params (IRQ and memory
region) and pass them to the backend and update guest device-tree to
create a DT node for the Virtio devices.

Add special support for I2C and GPIO devices, which require the
"compatible" DT property to be set, among other device specific
properties. Support for generic virtio devices is also added, which just
need a MMIO node but not any special DT properties, for such devices the
user needs to pass "virtio,device" in the "type" string.

The parsing of generic virtio device configurations will be done in a
separate commit.

Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 tools/libs/light/Makefile                 |   1 +
 tools/libs/light/libxl_arm.c              | 100 +++++++++++++++
 tools/libs/light/libxl_create.c           |   4 +
 tools/libs/light/libxl_internal.h         |   6 +
 tools/libs/light/libxl_types.idl          |  18 +++
 tools/libs/light/libxl_types_internal.idl |   1 +
 tools/libs/light/libxl_virtio.c           | 144 ++++++++++++++++++++++
 7 files changed, 274 insertions(+)
 create mode 100644 tools/libs/light/libxl_virtio.c

diff --git a/tools/libs/light/Makefile b/tools/libs/light/Makefile
index 374be1cfab25..4fddcc6f51d7 100644
--- a/tools/libs/light/Makefile
+++ b/tools/libs/light/Makefile
@@ -106,6 +106,7 @@ OBJS-y += libxl_vdispl.o
 OBJS-y += libxl_pvcalls.o
 OBJS-y += libxl_vsnd.o
 OBJS-y += libxl_vkb.o
+OBJS-y += libxl_virtio.o
 OBJS-y += libxl_genid.o
 OBJS-y += _libxl_types.o
 OBJS-y += libxl_flask.o
diff --git a/tools/libs/light/libxl_arm.c b/tools/libs/light/libxl_arm.c
index fa3d61f1e882..ddc7b2a15975 100644
--- a/tools/libs/light/libxl_arm.c
+++ b/tools/libs/light/libxl_arm.c
@@ -113,6 +113,19 @@ int libxl__arch_domain_prepare_config(libxl__gc *gc,
         }
     }
 
+    for (i = 0; i < d_config->num_virtios; i++) {
+        libxl_device_virtio *virtio = &d_config->virtios[i];
+
+        if (virtio->transport != LIBXL_VIRTIO_TRANSPORT_MMIO)
+            continue;
+
+        rc = alloc_virtio_mmio_params(gc, &virtio->base, &virtio->irq,
+                                      &virtio_mmio_base, &virtio_mmio_irq);
+
+        if (rc)
+            return rc;
+    }
+
     /*
      * Every virtio-mmio device uses one emulated SPI. If Virtio devices are
      * present, make sure that we allocate enough SPIs for them.
@@ -956,6 +969,79 @@ static int make_virtio_mmio_node(libxl__gc *gc, void *fdt, uint64_t base,
     return fdt_end_node(fdt);
 }
 
+/*
+ * The DT bindings for I2C device are present here:
+ *
+ * https://www.kernel.org/doc/Documentation/devicetree/bindings/i2c/i2c-virtio.yaml
+ */
+static int make_virtio_mmio_node_i2c(libxl__gc *gc, void *fdt)
+{
+    int res;
+
+    res = fdt_begin_node(fdt, "i2c");
+    if (res) return res;
+
+    res = fdt_property_compat(gc, fdt, 1, VIRTIO_DEVICE_TYPE_I2C);
+    if (res) return res;
+
+    return fdt_end_node(fdt);
+}
+
+/*
+ * The DT bindings for GPIO device are present here:
+ *
+ * https://www.kernel.org/doc/Documentation/devicetree/bindings/gpio/gpio-virtio.yaml
+ */
+static int make_virtio_mmio_node_gpio(libxl__gc *gc, void *fdt)
+{
+    int res;
+
+    res = fdt_begin_node(fdt, "gpio");
+    if (res) return res;
+
+    res = fdt_property_compat(gc, fdt, 1, VIRTIO_DEVICE_TYPE_GPIO);
+    if (res) return res;
+
+    res = fdt_property(fdt, "gpio-controller", NULL, 0);
+    if (res) return res;
+
+    res = fdt_property_cell(fdt, "#gpio-cells", 2);
+    if (res) return res;
+
+    res = fdt_property(fdt, "interrupt-controller", NULL, 0);
+    if (res) return res;
+
+    res = fdt_property_cell(fdt, "#interrupt-cells", 2);
+    if (res) return res;
+
+    return fdt_end_node(fdt);
+}
+
+static int make_virtio_mmio_node_device(libxl__gc *gc, void *fdt, uint64_t base,
+                                        uint32_t irq, const char *type,
+                                        uint32_t backend_domid)
+{
+    int res;
+
+    res = make_virtio_mmio_node_common(gc, fdt, base, irq, backend_domid);
+    if (res) return res;
+
+    /* Add device specific nodes */
+    if (!strcmp(type, VIRTIO_DEVICE_TYPE_I2C)) {
+        res = make_virtio_mmio_node_i2c(gc, fdt);
+        if (res) return res;
+    } else if (!strcmp(type, VIRTIO_DEVICE_TYPE_GPIO)) {
+        res = make_virtio_mmio_node_gpio(gc, fdt);
+        if (res) return res;
+    } else if (strcmp(type, VIRTIO_DEVICE_TYPE_GENERIC)) {
+        /* Doesn't match generic virtio device */
+        LOG(ERROR, "Invalid type for virtio device: %s", type);
+        return -EINVAL;
+    }
+
+    return fdt_end_node(fdt);
+}
+
 static const struct arch_info *get_arch_info(libxl__gc *gc,
                                              const struct xc_dom_image *dom)
 {
@@ -1277,6 +1363,20 @@ static int libxl__prepare_dtb(libxl__gc *gc, libxl_domain_config *d_config,
             }
         }
 
+        for (i = 0; i < d_config->num_virtios; i++) {
+            libxl_device_virtio *virtio = &d_config->virtios[i];
+
+            if (virtio->transport != LIBXL_VIRTIO_TRANSPORT_MMIO)
+                continue;
+
+            if (virtio->backend_domid != LIBXL_TOOLSTACK_DOMID)
+                iommu_needed = true;
+
+            FDT( make_virtio_mmio_node_device(gc, fdt, virtio->base,
+                                              virtio->irq, virtio->type,
+                                              virtio->backend_domid) );
+        }
+
         /*
          * The iommu node should be created only once for all virtio-mmio
          * devices.
diff --git a/tools/libs/light/libxl_create.c b/tools/libs/light/libxl_create.c
index 612eacfc7fac..beec3f6b6fec 100644
--- a/tools/libs/light/libxl_create.c
+++ b/tools/libs/light/libxl_create.c
@@ -1752,6 +1752,10 @@ static void domcreate_launch_dm(libxl__egc *egc, libxl__multidev *multidev,
         libxl__device_add(gc, domid, &libxl__pvcallsif_devtype,
                           &d_config->pvcallsifs[i]);
 
+    for (i = 0; i < d_config->num_virtios; i++)
+        libxl__device_add(gc, domid, &libxl__virtio_devtype,
+                          &d_config->virtios[i]);
+
     switch (d_config->c_info.type) {
     case LIBXL_DOMAIN_TYPE_HVM:
     {
diff --git a/tools/libs/light/libxl_internal.h b/tools/libs/light/libxl_internal.h
index a7c447c10e5f..97e1e66d98af 100644
--- a/tools/libs/light/libxl_internal.h
+++ b/tools/libs/light/libxl_internal.h
@@ -166,6 +166,11 @@
 /* Convert pfn to physical address space. */
 #define pfn_to_paddr(x) ((uint64_t)(x) << XC_PAGE_SHIFT)
 
+/* Virtio device types */
+#define VIRTIO_DEVICE_TYPE_GENERIC   "virtio,device"
+#define VIRTIO_DEVICE_TYPE_GPIO      "virtio,device22"
+#define VIRTIO_DEVICE_TYPE_I2C       "virtio,device29"
+
 /* logging */
 _hidden void libxl__logv(libxl_ctx *ctx, xentoollog_level msglevel, int errnoval,
              const char *file /* may be 0 */, int line /* ignored if !file */,
@@ -4003,6 +4008,7 @@ static inline int *libxl__device_type_get_num(
 
 extern const libxl__device_type libxl__vfb_devtype;
 extern const libxl__device_type libxl__vkb_devtype;
+extern const libxl__device_type libxl__virtio_devtype;
 extern const libxl__device_type libxl__disk_devtype;
 extern const libxl__device_type libxl__nic_devtype;
 extern const libxl__device_type libxl__vtpm_devtype;
diff --git a/tools/libs/light/libxl_types.idl b/tools/libs/light/libxl_types.idl
index 9e3d33cb5a59..0cfad8508dbd 100644
--- a/tools/libs/light/libxl_types.idl
+++ b/tools/libs/light/libxl_types.idl
@@ -278,6 +278,11 @@ libxl_vkb_backend = Enumeration("vkb_backend", [
     (2, "LINUX")
     ])
 
+libxl_virtio_transport = Enumeration("virtio_transport", [
+    (0, "UNKNOWN"),
+    (1, "MMIO"),
+    ])
+
 libxl_passthrough = Enumeration("passthrough", [
     (0, "default"),
     (1, "disabled"),
@@ -703,6 +708,18 @@ libxl_device_vkb = Struct("device_vkb", [
     ("multi_touch_num_contacts", uint32)
     ])
 
+libxl_device_virtio = Struct("device_virtio", [
+    ("backend_domid", libxl_domid),
+    ("backend_domname", string),
+    ("type", string),
+    ("transport", libxl_virtio_transport),
+    ("devid", libxl_devid),
+    # Note that virtio-mmio parameters (irq and base) are for internal
+    # use by libxl and can't be modified.
+    ("irq", uint32),
+    ("base", uint64)
+    ])
+
 libxl_device_disk = Struct("device_disk", [
     ("backend_domid", libxl_domid),
     ("backend_domname", string),
@@ -980,6 +997,7 @@ libxl_domain_config = Struct("domain_config", [
     ("dtdevs", Array(libxl_device_dtdev, "num_dtdevs")),
     ("vfbs", Array(libxl_device_vfb, "num_vfbs")),
     ("vkbs", Array(libxl_device_vkb, "num_vkbs")),
+    ("virtios", Array(libxl_device_virtio, "num_virtios")),
     ("vtpms", Array(libxl_device_vtpm, "num_vtpms")),
     ("p9s", Array(libxl_device_p9, "num_p9s")),
     ("pvcallsifs", Array(libxl_device_pvcallsif, "num_pvcallsifs")),
diff --git a/tools/libs/light/libxl_types_internal.idl b/tools/libs/light/libxl_types_internal.idl
index fb0f4f23d7c2..e24288f1a59e 100644
--- a/tools/libs/light/libxl_types_internal.idl
+++ b/tools/libs/light/libxl_types_internal.idl
@@ -33,6 +33,7 @@ libxl__device_kind = Enumeration("device_kind", [
     (15, "VSND"),
     (16, "VINPUT"),
     (17, "VIRTIO_DISK"),
+    (18, "VIRTIO"),
     ])
 
 libxl__console_backend = Enumeration("console_backend", [
diff --git a/tools/libs/light/libxl_virtio.c b/tools/libs/light/libxl_virtio.c
new file mode 100644
index 000000000000..6a38def2faf5
--- /dev/null
+++ b/tools/libs/light/libxl_virtio.c
@@ -0,0 +1,144 @@
+/*
+ * Copyright (C) 2022 Linaro Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ */
+
+#include "libxl_internal.h"
+
+static int libxl__device_virtio_setdefault(libxl__gc *gc, uint32_t domid,
+                                           libxl_device_virtio *virtio,
+                                           bool hotplug)
+{
+    return libxl__resolve_domid(gc, virtio->backend_domname,
+                                &virtio->backend_domid);
+}
+
+static int libxl__device_from_virtio(libxl__gc *gc, uint32_t domid,
+                                     libxl_device_virtio *virtio,
+                                     libxl__device *device)
+{
+    device->backend_devid   = virtio->devid;
+    device->backend_domid   = virtio->backend_domid;
+    device->devid           = virtio->devid;
+    device->domid           = domid;
+
+    device->backend_kind    = LIBXL__DEVICE_KIND_VIRTIO;
+    device->kind            = LIBXL__DEVICE_KIND_VIRTIO;
+
+    return 0;
+}
+
+static int libxl__set_xenstore_virtio(libxl__gc *gc, uint32_t domid,
+                                      libxl_device_virtio *virtio,
+                                      flexarray_t *back, flexarray_t *front,
+                                      flexarray_t *ro_front)
+{
+    const char *transport = libxl_virtio_transport_to_string(virtio->transport);
+
+    flexarray_append_pair(back, "irq", GCSPRINTF("%u", virtio->irq));
+    flexarray_append_pair(back, "base", GCSPRINTF("%lu", virtio->base));
+    flexarray_append_pair(back, "type", GCSPRINTF("%s", virtio->type));
+    flexarray_append_pair(back, "transport", GCSPRINTF("%s", transport));
+
+    flexarray_append_pair(front, "irq", GCSPRINTF("%u", virtio->irq));
+    flexarray_append_pair(front, "base", GCSPRINTF("%lu", virtio->base));
+    flexarray_append_pair(front, "type", GCSPRINTF("%s", virtio->type));
+    flexarray_append_pair(front, "transport", GCSPRINTF("%s", transport));
+
+    return 0;
+}
+
+static int libxl__virtio_from_xenstore(libxl__gc *gc, const char *libxl_path,
+                                       libxl_devid devid,
+                                       libxl_device_virtio *virtio)
+{
+    const char *be_path, *tmp = NULL;
+    int rc;
+
+    virtio->devid = devid;
+
+    rc = libxl__xs_read_mandatory(gc, XBT_NULL,
+                                  GCSPRINTF("%s/backend", libxl_path),
+                                  &be_path);
+    if (rc) goto out;
+
+    rc = libxl__backendpath_parse_domid(gc, be_path, &virtio->backend_domid);
+    if (rc) goto out;
+
+    rc = libxl__xs_read_checked(gc, XBT_NULL,
+				GCSPRINTF("%s/irq", be_path), &tmp);
+    if (rc) goto out;
+
+    if (tmp) {
+        virtio->irq = strtoul(tmp, NULL, 0);
+    }
+
+    tmp = NULL;
+    rc = libxl__xs_read_checked(gc, XBT_NULL,
+				GCSPRINTF("%s/base", be_path), &tmp);
+    if (rc) goto out;
+
+    if (tmp) {
+        virtio->base = strtoul(tmp, NULL, 0);
+    }
+
+    tmp = NULL;
+    rc = libxl__xs_read_checked(gc, XBT_NULL,
+				GCSPRINTF("%s/transport", be_path), &tmp);
+    if (rc) goto out;
+
+    if (tmp) {
+        if (!strcmp(tmp, "mmio")) {
+            virtio->transport = LIBXL_VIRTIO_TRANSPORT_MMIO;
+        } else {
+            return ERROR_INVAL;
+        }
+    }
+
+    tmp = NULL;
+    rc = libxl__xs_read_checked(gc, XBT_NULL,
+				GCSPRINTF("%s/type", be_path), &tmp);
+    if (rc) goto out;
+
+    if (tmp) {
+        int len = sizeof(VIRTIO_DEVICE_TYPE_GENERIC) - 1;
+
+        if (!strncmp(tmp, VIRTIO_DEVICE_TYPE_GENERIC, len)) {
+            virtio->type = libxl__strdup(NOGC, tmp);
+        } else {
+            return ERROR_INVAL;
+        }
+    }
+
+out:
+    return rc;
+}
+
+static LIBXL_DEFINE_UPDATE_DEVID(virtio)
+
+#define libxl__add_virtios NULL
+#define libxl_device_virtio_compare NULL
+
+DEFINE_DEVICE_TYPE_STRUCT(virtio, VIRTIO, virtios,
+    .set_xenstore_config = (device_set_xenstore_config_fn_t)
+                           libxl__set_xenstore_virtio,
+    .from_xenstore = (device_from_xenstore_fn_t)libxl__virtio_from_xenstore,
+    .skip_attach = 1
+);
+
+/*
+ * Local variables:
+ * mode: C
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
-- 
2.31.1.272.g89b43f80a514

Re: [PATCH V9 1/3] libxl: Add support for generic virtio device

[Jan Beulich]

On 13.12.2022 11:08, Viresh Kumar wrote:
> This patch adds basic support for configuring and assisting generic
> Virtio backends, which could run in any domain.
> 
> An example of domain configuration for mmio based Virtio I2C device is:
> virtio = ["type=virtio,device22,transport=mmio"]
> 
> To make this work on Arm, allocate Virtio MMIO params (IRQ and memory
> region) and pass them to the backend and update guest device-tree to
> create a DT node for the Virtio devices.
> 
> Add special support for I2C and GPIO devices, which require the
> "compatible" DT property to be set, among other device specific
> properties. Support for generic virtio devices is also added, which just
> need a MMIO node but not any special DT properties, for such devices the
> user needs to pass "virtio,device" in the "type" string.
> 
> The parsing of generic virtio device configurations will be done in a
> separate commit.
> 
> Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

Please can you arrange tags in time order, which would mean R-b past any
S-o-b? I'll try to remember to swap them while committing, but in the
future please save committers from needing to do so.

Jan

Re: [PATCH V9 1/3] libxl: Add support for generic virtio device

[Viresh Kumar]

On 13-12-22, 12:14, Jan Beulich wrote:
> Please can you arrange tags in time order, which would mean R-b past any
> S-o-b? I'll try to remember to swap them while committing, but in the
> future please save committers from needing to do so.

I was confused if Reviewed-by's should be after of before Author's
signed-off, understood it now. Will remember that going ahead. Thanks.

-- 
viresh

Re: [PATCH V9 1/3] libxl: Add support for generic virtio device

[Oleksandr Tyshchenko]

On 13.12.22 12:08, Viresh Kumar wrote:

Hello Viresh

> This patch adds basic support for configuring and assisting generic
> Virtio backends, which could run in any domain.
> 
> An example of domain configuration for mmio based Virtio I2C device is:
> virtio = ["type=virtio,device22,transport=mmio"]
> 
> To make this work on Arm, allocate Virtio MMIO params (IRQ and memory
> region) and pass them to the backend and update guest device-tree to
> create a DT node for the Virtio devices.
> 
> Add special support for I2C and GPIO devices, which require the
> "compatible" DT property to be set, among other device specific
> properties. Support for generic virtio devices is also added, which just
> need a MMIO node but not any special DT properties, for such devices the
> user needs to pass "virtio,device" in the "type" string.
> 
> The parsing of generic virtio device configurations will be done in a
> separate commit.
> 
> Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
>   tools/libs/light/Makefile                 |   1 +
>   tools/libs/light/libxl_arm.c              | 100 +++++++++++++++
>   tools/libs/light/libxl_create.c           |   4 +
>   tools/libs/light/libxl_internal.h         |   6 +
>   tools/libs/light/libxl_types.idl          |  18 +++
>   tools/libs/light/libxl_types_internal.idl |   1 +
>   tools/libs/light/libxl_virtio.c           | 144 ++++++++++++++++++++++
>   7 files changed, 274 insertions(+)
>   create mode 100644 tools/libs/light/libxl_virtio.c
> 
> diff --git a/tools/libs/light/Makefile b/tools/libs/light/Makefile
> index 374be1cfab25..4fddcc6f51d7 100644
> --- a/tools/libs/light/Makefile
> +++ b/tools/libs/light/Makefile
> @@ -106,6 +106,7 @@ OBJS-y += libxl_vdispl.o
>   OBJS-y += libxl_pvcalls.o
>   OBJS-y += libxl_vsnd.o
>   OBJS-y += libxl_vkb.o
> +OBJS-y += libxl_virtio.o
>   OBJS-y += libxl_genid.o
>   OBJS-y += _libxl_types.o
>   OBJS-y += libxl_flask.o
> diff --git a/tools/libs/light/libxl_arm.c b/tools/libs/light/libxl_arm.c
> index fa3d61f1e882..ddc7b2a15975 100644
> --- a/tools/libs/light/libxl_arm.c
> +++ b/tools/libs/light/libxl_arm.c
> @@ -113,6 +113,19 @@ int libxl__arch_domain_prepare_config(libxl__gc *gc,
>           }
>       }
>   
> +    for (i = 0; i < d_config->num_virtios; i++) {
> +        libxl_device_virtio *virtio = &d_config->virtios[i];
> +
> +        if (virtio->transport != LIBXL_VIRTIO_TRANSPORT_MMIO)
> +            continue;
> +
> +        rc = alloc_virtio_mmio_params(gc, &virtio->base, &virtio->irq,
> +                                      &virtio_mmio_base, &virtio_mmio_irq);
> +
> +        if (rc)
> +            return rc;
> +    }
> +
>       /*
>        * Every virtio-mmio device uses one emulated SPI. If Virtio devices are
>        * present, make sure that we allocate enough SPIs for them.
> @@ -956,6 +969,79 @@ static int make_virtio_mmio_node(libxl__gc *gc, void *fdt, uint64_t base,
>       return fdt_end_node(fdt);
>   }
>   
> +/*
> + * The DT bindings for I2C device are present here:
> + *
> + * https://www.kernel.org/doc/Documentation/devicetree/bindings/i2c/i2c-virtio.yaml
> + */
> +static int make_virtio_mmio_node_i2c(libxl__gc *gc, void *fdt)
> +{
> +    int res;
> +
> +    res = fdt_begin_node(fdt, "i2c");
> +    if (res) return res;
> +
> +    res = fdt_property_compat(gc, fdt, 1, VIRTIO_DEVICE_TYPE_I2C);
> +    if (res) return res;
> +
> +    return fdt_end_node(fdt);
> +}
> +
> +/*
> + * The DT bindings for GPIO device are present here:
> + *
> + * https://www.kernel.org/doc/Documentation/devicetree/bindings/gpio/gpio-virtio.yaml
> + */
> +static int make_virtio_mmio_node_gpio(libxl__gc *gc, void *fdt)
> +{
> +    int res;
> +
> +    res = fdt_begin_node(fdt, "gpio");
> +    if (res) return res;
> +
> +    res = fdt_property_compat(gc, fdt, 1, VIRTIO_DEVICE_TYPE_GPIO);
> +    if (res) return res;
> +
> +    res = fdt_property(fdt, "gpio-controller", NULL, 0);
> +    if (res) return res;
> +
> +    res = fdt_property_cell(fdt, "#gpio-cells", 2);
> +    if (res) return res;
> +
> +    res = fdt_property(fdt, "interrupt-controller", NULL, 0);
> +    if (res) return res;
> +
> +    res = fdt_property_cell(fdt, "#interrupt-cells", 2);
> +    if (res) return res;
> +
> +    return fdt_end_node(fdt);
> +}
> +
> +static int make_virtio_mmio_node_device(libxl__gc *gc, void *fdt, uint64_t base,
> +                                        uint32_t irq, const char *type,
> +                                        uint32_t backend_domid)
> +{
> +    int res;
> +
> +    res = make_virtio_mmio_node_common(gc, fdt, base, irq, backend_domid);
> +    if (res) return res;
> +
> +    /* Add device specific nodes */
> +    if (!strcmp(type, VIRTIO_DEVICE_TYPE_I2C)) {
> +        res = make_virtio_mmio_node_i2c(gc, fdt);
> +        if (res) return res;
> +    } else if (!strcmp(type, VIRTIO_DEVICE_TYPE_GPIO)) {
> +        res = make_virtio_mmio_node_gpio(gc, fdt);
> +        if (res) return res;
> +    } else if (strcmp(type, VIRTIO_DEVICE_TYPE_GENERIC)) {
> +        /* Doesn't match generic virtio device */
> +        LOG(ERROR, "Invalid type for virtio device: %s", type);
> +        return -EINVAL;
> +    }
> +
> +    return fdt_end_node(fdt);
> +}
> +
>   static const struct arch_info *get_arch_info(libxl__gc *gc,
>                                                const struct xc_dom_image *dom)
>   {
> @@ -1277,6 +1363,20 @@ static int libxl__prepare_dtb(libxl__gc *gc, libxl_domain_config *d_config,
>               }
>           }
>   
> +        for (i = 0; i < d_config->num_virtios; i++) {
> +            libxl_device_virtio *virtio = &d_config->virtios[i];
> +
> +            if (virtio->transport != LIBXL_VIRTIO_TRANSPORT_MMIO)
> +                continue;
> +
> +            if (virtio->backend_domid != LIBXL_TOOLSTACK_DOMID)
> +                iommu_needed = true;
> +
> +            FDT( make_virtio_mmio_node_device(gc, fdt, virtio->base,
> +                                              virtio->irq, virtio->type,
> +                                              virtio->backend_domid) );
> +        }
> +
>           /*
>            * The iommu node should be created only once for all virtio-mmio
>            * devices.
> diff --git a/tools/libs/light/libxl_create.c b/tools/libs/light/libxl_create.c
> index 612eacfc7fac..beec3f6b6fec 100644
> --- a/tools/libs/light/libxl_create.c
> +++ b/tools/libs/light/libxl_create.c
> @@ -1752,6 +1752,10 @@ static void domcreate_launch_dm(libxl__egc *egc, libxl__multidev *multidev,
>           libxl__device_add(gc, domid, &libxl__pvcallsif_devtype,
>                             &d_config->pvcallsifs[i]);
>   
> +    for (i = 0; i < d_config->num_virtios; i++)
> +        libxl__device_add(gc, domid, &libxl__virtio_devtype,
> +                          &d_config->virtios[i]);
> +
>       switch (d_config->c_info.type) {
>       case LIBXL_DOMAIN_TYPE_HVM:
>       {
> diff --git a/tools/libs/light/libxl_internal.h b/tools/libs/light/libxl_internal.h
> index a7c447c10e5f..97e1e66d98af 100644
> --- a/tools/libs/light/libxl_internal.h
> +++ b/tools/libs/light/libxl_internal.h
> @@ -166,6 +166,11 @@
>   /* Convert pfn to physical address space. */
>   #define pfn_to_paddr(x) ((uint64_t)(x) << XC_PAGE_SHIFT)
>   
> +/* Virtio device types */
> +#define VIRTIO_DEVICE_TYPE_GENERIC   "virtio,device"
> +#define VIRTIO_DEVICE_TYPE_GPIO      "virtio,device22"
> +#define VIRTIO_DEVICE_TYPE_I2C       "virtio,device29"


Sorry for pointing this out only now, I have just realized that this 
doesn't match device-tree bindings. According to the bindings they 
should be the other way around:

#define VIRTIO_DEVICE_TYPE_I2C      "virtio,device22"
#define VIRTIO_DEVICE_TYPE_GPIO       "virtio,device29"


> +
>   /* logging */
>   _hidden void libxl__logv(libxl_ctx *ctx, xentoollog_level msglevel, int errnoval,
>                const char *file /* may be 0 */, int line /* ignored if !file */,
> @@ -4003,6 +4008,7 @@ static inline int *libxl__device_type_get_num(
>   
>   extern const libxl__device_type libxl__vfb_devtype;
>   extern const libxl__device_type libxl__vkb_devtype;
> +extern const libxl__device_type libxl__virtio_devtype;
>   extern const libxl__device_type libxl__disk_devtype;
>   extern const libxl__device_type libxl__nic_devtype;
>   extern const libxl__device_type libxl__vtpm_devtype;
> diff --git a/tools/libs/light/libxl_types.idl b/tools/libs/light/libxl_types.idl
> index 9e3d33cb5a59..0cfad8508dbd 100644
> --- a/tools/libs/light/libxl_types.idl
> +++ b/tools/libs/light/libxl_types.idl
> @@ -278,6 +278,11 @@ libxl_vkb_backend = Enumeration("vkb_backend", [
>       (2, "LINUX")
>       ])
>   
> +libxl_virtio_transport = Enumeration("virtio_transport", [
> +    (0, "UNKNOWN"),
> +    (1, "MMIO"),
> +    ])
> +
>   libxl_passthrough = Enumeration("passthrough", [
>       (0, "default"),
>       (1, "disabled"),
> @@ -703,6 +708,18 @@ libxl_device_vkb = Struct("device_vkb", [
>       ("multi_touch_num_contacts", uint32)
>       ])
>   
> +libxl_device_virtio = Struct("device_virtio", [
> +    ("backend_domid", libxl_domid),
> +    ("backend_domname", string),
> +    ("type", string),
> +    ("transport", libxl_virtio_transport),
> +    ("devid", libxl_devid),
> +    # Note that virtio-mmio parameters (irq and base) are for internal
> +    # use by libxl and can't be modified.
> +    ("irq", uint32),
> +    ("base", uint64)
> +    ])
> +
>   libxl_device_disk = Struct("device_disk", [
>       ("backend_domid", libxl_domid),
>       ("backend_domname", string),
> @@ -980,6 +997,7 @@ libxl_domain_config = Struct("domain_config", [
>       ("dtdevs", Array(libxl_device_dtdev, "num_dtdevs")),
>       ("vfbs", Array(libxl_device_vfb, "num_vfbs")),
>       ("vkbs", Array(libxl_device_vkb, "num_vkbs")),
> +    ("virtios", Array(libxl_device_virtio, "num_virtios")),
>       ("vtpms", Array(libxl_device_vtpm, "num_vtpms")),
>       ("p9s", Array(libxl_device_p9, "num_p9s")),
>       ("pvcallsifs", Array(libxl_device_pvcallsif, "num_pvcallsifs")),
> diff --git a/tools/libs/light/libxl_types_internal.idl b/tools/libs/light/libxl_types_internal.idl
> index fb0f4f23d7c2..e24288f1a59e 100644
> --- a/tools/libs/light/libxl_types_internal.idl
> +++ b/tools/libs/light/libxl_types_internal.idl
> @@ -33,6 +33,7 @@ libxl__device_kind = Enumeration("device_kind", [
>       (15, "VSND"),
>       (16, "VINPUT"),
>       (17, "VIRTIO_DISK"),
> +    (18, "VIRTIO"),
>       ])
>   
>   libxl__console_backend = Enumeration("console_backend", [
> diff --git a/tools/libs/light/libxl_virtio.c b/tools/libs/light/libxl_virtio.c
> new file mode 100644
> index 000000000000..6a38def2faf5
> --- /dev/null
> +++ b/tools/libs/light/libxl_virtio.c
> @@ -0,0 +1,144 @@
> +/*
> + * Copyright (C) 2022 Linaro Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU Lesser General Public License as published
> + * by the Free Software Foundation; version 2.1 only. with the special
> + * exception on linking described in file LICENSE.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU Lesser General Public License for more details.
> + */
> +
> +#include "libxl_internal.h"
> +
> +static int libxl__device_virtio_setdefault(libxl__gc *gc, uint32_t domid,
> +                                           libxl_device_virtio *virtio,
> +                                           bool hotplug)
> +{
> +    return libxl__resolve_domid(gc, virtio->backend_domname,
> +                                &virtio->backend_domid);
> +}
> +
> +static int libxl__device_from_virtio(libxl__gc *gc, uint32_t domid,
> +                                     libxl_device_virtio *virtio,
> +                                     libxl__device *device)
> +{
> +    device->backend_devid   = virtio->devid;
> +    device->backend_domid   = virtio->backend_domid;
> +    device->devid           = virtio->devid;
> +    device->domid           = domid;
> +
> +    device->backend_kind    = LIBXL__DEVICE_KIND_VIRTIO;
> +    device->kind            = LIBXL__DEVICE_KIND_VIRTIO;
> +
> +    return 0;
> +}
> +
> +static int libxl__set_xenstore_virtio(libxl__gc *gc, uint32_t domid,
> +                                      libxl_device_virtio *virtio,
> +                                      flexarray_t *back, flexarray_t *front,
> +                                      flexarray_t *ro_front)
> +{
> +    const char *transport = libxl_virtio_transport_to_string(virtio->transport);
> +
> +    flexarray_append_pair(back, "irq", GCSPRINTF("%u", virtio->irq));
> +    flexarray_append_pair(back, "base", GCSPRINTF("%lu", virtio->base));
> +    flexarray_append_pair(back, "type", GCSPRINTF("%s", virtio->type));
> +    flexarray_append_pair(back, "transport", GCSPRINTF("%s", transport));
> +
> +    flexarray_append_pair(front, "irq", GCSPRINTF("%u", virtio->irq));
> +    flexarray_append_pair(front, "base", GCSPRINTF("%lu", virtio->base));
> +    flexarray_append_pair(front, "type", GCSPRINTF("%s", virtio->type));
> +    flexarray_append_pair(front, "transport", GCSPRINTF("%s", transport));
> +
> +    return 0;
> +}
> +
> +static int libxl__virtio_from_xenstore(libxl__gc *gc, const char *libxl_path,
> +                                       libxl_devid devid,
> +                                       libxl_device_virtio *virtio)
> +{
> +    const char *be_path, *tmp = NULL;
> +    int rc;
> +
> +    virtio->devid = devid;
> +
> +    rc = libxl__xs_read_mandatory(gc, XBT_NULL,
> +                                  GCSPRINTF("%s/backend", libxl_path),
> +                                  &be_path);
> +    if (rc) goto out;
> +
> +    rc = libxl__backendpath_parse_domid(gc, be_path, &virtio->backend_domid);
> +    if (rc) goto out;
> +
> +    rc = libxl__xs_read_checked(gc, XBT_NULL,
> +				GCSPRINTF("%s/irq", be_path), &tmp);
> +    if (rc) goto out;
> +
> +    if (tmp) {
> +        virtio->irq = strtoul(tmp, NULL, 0);
> +    }
> +
> +    tmp = NULL;
> +    rc = libxl__xs_read_checked(gc, XBT_NULL,
> +				GCSPRINTF("%s/base", be_path), &tmp);
> +    if (rc) goto out;
> +
> +    if (tmp) {
> +        virtio->base = strtoul(tmp, NULL, 0);
> +    }
> +
> +    tmp = NULL;
> +    rc = libxl__xs_read_checked(gc, XBT_NULL,
> +				GCSPRINTF("%s/transport", be_path), &tmp);
> +    if (rc) goto out;
> +
> +    if (tmp) {
> +        if (!strcmp(tmp, "mmio")) {
> +            virtio->transport = LIBXL_VIRTIO_TRANSPORT_MMIO;
> +        } else {
> +            return ERROR_INVAL;
> +        }
> +    }
> +
> +    tmp = NULL;
> +    rc = libxl__xs_read_checked(gc, XBT_NULL,
> +				GCSPRINTF("%s/type", be_path), &tmp);
> +    if (rc) goto out;
> +
> +    if (tmp) {
> +        int len = sizeof(VIRTIO_DEVICE_TYPE_GENERIC) - 1;
> +
> +        if (!strncmp(tmp, VIRTIO_DEVICE_TYPE_GENERIC, len)) {
> +            virtio->type = libxl__strdup(NOGC, tmp);
> +        } else {
> +            return ERROR_INVAL;
> +        }
> +    }
> +
> +out:
> +    return rc;
> +}
> +
> +static LIBXL_DEFINE_UPDATE_DEVID(virtio)
> +
> +#define libxl__add_virtios NULL
> +#define libxl_device_virtio_compare NULL
> +
> +DEFINE_DEVICE_TYPE_STRUCT(virtio, VIRTIO, virtios,
> +    .set_xenstore_config = (device_set_xenstore_config_fn_t)
> +                           libxl__set_xenstore_virtio,
> +    .from_xenstore = (device_from_xenstore_fn_t)libxl__virtio_from_xenstore,
> +    .skip_attach = 1
> +);
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-basic-offset: 4
> + * indent-tabs-mode: nil
> + * End:
> + */

Re: [PATCH V9 1/3] libxl: Add support for generic virtio device

[Viresh Kumar]

On 13-12-22, 13:45, Oleksandr Tyshchenko wrote:
> On 13.12.22 12:08, Viresh Kumar wrote:
> > +/* Virtio device types */
> > +#define VIRTIO_DEVICE_TYPE_GENERIC   "virtio,device"
> > +#define VIRTIO_DEVICE_TYPE_GPIO      "virtio,device22"
> > +#define VIRTIO_DEVICE_TYPE_I2C       "virtio,device29"
> 
> 
> Sorry for pointing this out only now, I have just realized that this doesn't
> match device-tree bindings. According to the bindings they should be the
> other way around:
> 
> #define VIRTIO_DEVICE_TYPE_I2C      "virtio,device22"
> #define VIRTIO_DEVICE_TYPE_GPIO       "virtio,device29"

That's a shocker, as I definitely tested this.

Now that I went back and looked at how it didn't break my system, I
found the reason. The string passed in domu.conf in my case is the
valid one: "virtio,device22", which ended up creating a GPIO node
eventually, but with the compatible value of I2C. The kernel didn't
complain as for I2C only the compatible string is checked currently.

-- 
viresh

[PATCH V9 2/3] xl: Add support to parse generic virtio device

[Viresh Kumar]

This patch adds basic support for parsing generic Virtio backend.

An example of domain configuration for mmio based Virtio I2C device is:
virtio = ["type=virtio,device22,transport=mmio"]

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 tools/xl/xl_parse.c | 81 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)

diff --git a/tools/xl/xl_parse.c b/tools/xl/xl_parse.c
index 644ab8f8fd36..853e9f357a1a 100644
--- a/tools/xl/xl_parse.c
+++ b/tools/xl/xl_parse.c
@@ -1208,6 +1208,83 @@ static void parse_vkb_list(const XLU_Config *config,
     if (rc) exit(EXIT_FAILURE);
 }
 
+static int parse_virtio_config(libxl_device_virtio *virtio, char *token)
+{
+    char *oparg;
+    int rc;
+
+    if (MATCH_OPTION("backend", token, oparg)) {
+        virtio->backend_domname = strdup(oparg);
+    } else if (MATCH_OPTION("type", token, oparg)) {
+        virtio->type = strdup(oparg);
+    } else if (MATCH_OPTION("transport", token, oparg)) {
+        rc = libxl_virtio_transport_from_string(oparg, &virtio->transport);
+        if (rc) return rc;
+    } else {
+        fprintf(stderr, "Unknown string \"%s\" in virtio spec\n", token);
+        return -1;
+    }
+
+    return 0;
+}
+
+static void parse_virtio_list(const XLU_Config *config,
+                              libxl_domain_config *d_config)
+{
+    XLU_ConfigList *virtios;
+    const char *item;
+    char *buf = NULL, *oparg, *str = NULL;
+    int rc;
+
+    if (!xlu_cfg_get_list (config, "virtio", &virtios, 0, 0)) {
+        int entry = 0;
+        while ((item = xlu_cfg_get_listitem(virtios, entry)) != NULL) {
+            libxl_device_virtio *virtio;
+            char *p;
+
+            virtio = ARRAY_EXTEND_INIT(d_config->virtios, d_config->num_virtios,
+                                       libxl_device_virtio_init);
+
+            buf = strdup(item);
+
+            p = strtok(buf, ",");
+            while (p != NULL)
+            {
+                while (*p == ' ') p++;
+
+                // Type may contain a comma, do special handling.
+                if (MATCH_OPTION("type", p, oparg)) {
+                    if (!strncmp(oparg, "virtio", strlen("virtio"))) {
+                        char *p2 = strtok(NULL, ",");
+                        str = malloc(strlen(p) + strlen(p2) + 2);
+
+                        strcpy(str, p);
+                        strcat(str, ",");
+                        strcat(str, p2);
+                        p = str;
+                    }
+                }
+
+                rc = parse_virtio_config(virtio, p);
+                if (rc) goto out;
+
+                free(str);
+                str = NULL;
+                p = strtok(NULL, ",");
+            }
+
+            entry++;
+            free(buf);
+        }
+    }
+
+    return;
+
+out:
+    free(buf);
+    if (rc) exit(EXIT_FAILURE);
+}
+
 void parse_config_data(const char *config_source,
                        const char *config_data,
                        int config_len,
@@ -2753,6 +2830,10 @@ void parse_config_data(const char *config_source,
 
     parse_vkb_list(config, d_config);
 
+    d_config->virtios = NULL;
+    d_config->num_virtios = 0;
+    parse_virtio_list(config, d_config);
+
     xlu_cfg_get_defbool(config, "xend_suspend_evtchn_compat",
                         &c_info->xend_suspend_evtchn_compat, 0);
 
-- 
2.31.1.272.g89b43f80a514

Re: [PATCH V9 2/3] xl: Add support to parse generic virtio device

[Anthony PERARD]

On Tue, Dec 13, 2022 at 03:38:47PM +0530, Viresh Kumar wrote:
> This patch adds basic support for parsing generic Virtio backend.
> 
> An example of domain configuration for mmio based Virtio I2C device is:
> virtio = ["type=virtio,device22,transport=mmio"]
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>

Thanks,

-- 
Anthony PERARD

[PATCH V9 3/3] docs: Add documentation for generic virtio devices

[Viresh Kumar]

This patch updates xl.cfg man page with details of generic Virtio device
related information.

Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 docs/man/xl.cfg.5.pod.in | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
index ec444fb2ba79..024bceeb61b2 100644
--- a/docs/man/xl.cfg.5.pod.in
+++ b/docs/man/xl.cfg.5.pod.in
@@ -1585,6 +1585,39 @@ Set maximum height for pointer device.
 
 =back
 
+=item B<virtio=[ "VIRTIO_DEVICE_STRING", "VIRTIO_DEVICE_STRING", ...]>
+
+Specifies the Virtio devices to be provided to the guest.
+
+Each B<VIRTIO_DEVICE_STRING> is a comma-separated list of C<KEY=VALUE> settings
+from the following list. As a special case, a single comma is allowed in the
+VALUE of the "type" KEY, where the VALUE is set with "virtio,device<N>".
+
+=over 4
+
+=item B<backend=domain-id>
+
+Specifies the backend domain name or id, defaults to dom0.
+
+=item B<type=STRING>
+
+Specifies the compatible string for the specific Virtio device. The same will be
+written in the Device Tree compatible property of the Virtio device. For
+example, "type=virtio,device22" for the I2C device, whose device-tree binding is
+present here:
+
+L<https://www.kernel.org/doc/Documentation/devicetree/bindings/i2c/i2c-virtio.yaml>
+
+For generic virtio devices, where we don't need to set special or compatible
+properties in the Device Tree, the type field must be set to "virtio,device".
+
+=item B<transport=STRING>
+
+Specifies the transport mechanism for the Virtio device, only "mmio" is
+supported for now.
+
+=back
+
 =item B<tee="STRING">
 
 B<Arm only.> Set TEE type for the guest. TEE is a Trusted Execution
-- 
2.31.1.272.g89b43f80a514

Re: [PATCH V9 3/3] docs: Add documentation for generic virtio devices

[Oleksandr Tyshchenko]

On 13.12.22 12:08, Viresh Kumar wrote:


Hello Viresh

> This patch updates xl.cfg man page with details of generic Virtio device
> related information.
> 
> Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>


Now it looks perfect, thanks

Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

> ---
>   docs/man/xl.cfg.5.pod.in | 33 +++++++++++++++++++++++++++++++++
>   1 file changed, 33 insertions(+)
> 
> diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
> index ec444fb2ba79..024bceeb61b2 100644
> --- a/docs/man/xl.cfg.5.pod.in
> +++ b/docs/man/xl.cfg.5.pod.in
> @@ -1585,6 +1585,39 @@ Set maximum height for pointer device.
>   
>   =back
>   
> +=item B<virtio=[ "VIRTIO_DEVICE_STRING", "VIRTIO_DEVICE_STRING", ...]>
> +
> +Specifies the Virtio devices to be provided to the guest.
> +
> +Each B<VIRTIO_DEVICE_STRING> is a comma-separated list of C<KEY=VALUE> settings
> +from the following list. As a special case, a single comma is allowed in the
> +VALUE of the "type" KEY, where the VALUE is set with "virtio,device<N>".
> +
> +=over 4
> +
> +=item B<backend=domain-id>
> +
> +Specifies the backend domain name or id, defaults to dom0.
> +
> +=item B<type=STRING>
> +
> +Specifies the compatible string for the specific Virtio device. The same will be
> +written in the Device Tree compatible property of the Virtio device. For
> +example, "type=virtio,device22" for the I2C device, whose device-tree binding is
> +present here:
> +
> +L<https://www.kernel.org/doc/Documentation/devicetree/bindings/i2c/i2c-virtio.yaml>
> +
> +For generic virtio devices, where we don't need to set special or compatible
> +properties in the Device Tree, the type field must be set to "virtio,device".
> +
> +=item B<transport=STRING>
> +
> +Specifies the transport mechanism for the Virtio device, only "mmio" is
> +supported for now.
> +
> +=back
> +
>   =item B<tee="STRING">
>   
>   B<Arm only.> Set TEE type for the guest. TEE is a Trusted Execution