[RFC PATCH 2/3] libxl: Allow PCI device passthrough using -device Qemu command line

["Thierry Escande" <thierry.escande@xxxxxxxxxx>]

This change makes use of the new option 'hotplug' for host PCI devices
passthrough'd to the guest. If hotplug=0 is used in the pci device
configuration table, the device will be attached to the guest using the
Qemu command line as '-device xen-pci-passthrough,hostaddr=...'

The host device configuration is passed to the -device option as a json
array, just like it's done for hotplug using QMP. The json array is
created by a new internal function libxl__device_pci_get_qmp_json() that
is also used by pci_add_qmp_device_add().

Then, instead of sending the 'device_add' command, the device_add
callback is called to perform the 'query-pci' check to make sure the
passthrough'd device is present.

In the same way at shutdown, the device is not removed using QMP and
only the pci_remove_done() function is called.

As with QMP, the use of the 'hotplug=0' option honors the 'seize' option
by adding the PCI device to the assignable list if needed.

Example use:
 pci = [ "00:03.0,seize=1,hotplug=0" ]

Signed-off-by: Thierry Escande <thierry.escande@xxxxxxxxxx>
---
 tools/include/libxl.h             |  1 +
 tools/libs/light/libxl_dm.c       | 31 +++++++++++++++++++++++
 tools/libs/light/libxl_internal.h |  2 ++
 tools/libs/light/libxl_pci.c      | 41 +++++++++++++++++++++++--------
 4 files changed, 65 insertions(+), 10 deletions(-)

diff --git a/tools/include/libxl.h b/tools/include/libxl.h
index 7c098edab6..66fb07ad67 100644
--- a/tools/include/libxl.h
+++ b/tools/include/libxl.h
@@ -2666,6 +2666,7 @@ int libxl_device_pci_assignable_add(libxl_ctx *ctx, 
libxl_device_pci *pci, int r
 int libxl_device_pci_assignable_remove(libxl_ctx *ctx, libxl_device_pci *pci, 
int rebind);
 libxl_device_pci *libxl_device_pci_assignable_list(libxl_ctx *ctx, int *num);
 void libxl_device_pci_assignable_list_free(libxl_device_pci *list, int num);
+bool libxl_pci_assignable(libxl_ctx *ctx, libxl_device_pci *pci);
 
 /* CPUID handling */
 int libxl_cpuid_parse_config(libxl_cpuid_policy_list *cpuid, const char* str);
diff --git a/tools/libs/light/libxl_dm.c b/tools/libs/light/libxl_dm.c
index 511ec76a65..96bb620f87 100644
--- a/tools/libs/light/libxl_dm.c
+++ b/tools/libs/light/libxl_dm.c
@@ -1169,6 +1169,37 @@ static int libxl__build_device_model_args_new(libxl__gc 
*gc,
                     }
                 }
             }
+
+            if (guest_config->num_pcidevs) {
+                libxl_device_pci *pci;
+                libxl__json_object *qmp_json;
+                const char *json_str;
+#ifndef HAVE_LIBJSONC
+#   error Missing JSON library
+#endif
+                json_object *jso = NULL;
+
+                for (i = 0; i < guest_config->num_pcidevs; i++) {
+                    libxl_ctx *ctx = libxl__gc_owner(gc);
+                    pci = &guest_config->pcidevs[i];
+
+                    if (pci->hotplug)
+                        continue;
+
+                    if (!libxl_pci_assignable(ctx, pci) && pci->seize) {
+                        rc = libxl_device_pci_assignable_add(ctx, pci, 1);
+                        if (rc)
+                            return rc;
+                    }
+                    qmp_json = libxl__device_pci_get_qmp_json(gc, pci);
+                    rc = libxl__json_object_to_json_object(gc, &jso, qmp_json);
+                    if (rc)
+                        return rc;
+                    json_str = json_object_to_json_string_ext(jso,
+                                                              
JSON_C_TO_STRING_PLAIN);
+                    flexarray_vappend(dm_args, "-device", json_str, NULL);
+                }
+            }
         }
 
         if (libxl_defbool_val(b_info->u.hvm.nographic) && (!sdl && !vnc)) {
diff --git a/tools/libs/light/libxl_internal.h 
b/tools/libs/light/libxl_internal.h
index b65e0064b9..06b5a14409 100644
--- a/tools/libs/light/libxl_internal.h
+++ b/tools/libs/light/libxl_internal.h
@@ -1729,6 +1729,8 @@ _hidden int libxl__device_pci_setdefault(libxl__gc *gc, 
uint32_t domid,
                                          libxl_device_pci *pci, bool hotplug);
 _hidden bool libxl__is_igd_vga_passthru(libxl__gc *gc,
                                         const libxl_domain_config *d_config);
+_hidden libxl__json_object *libxl__device_pci_get_qmp_json(libxl__gc *gc,
+                                                         libxl_device_pci 
*pci);
 
 /* from libxl_dtdev */
 
diff --git a/tools/libs/light/libxl_pci.c b/tools/libs/light/libxl_pci.c
index 49d272d0de..3ef2c43412 100644
--- a/tools/libs/light/libxl_pci.c
+++ b/tools/libs/light/libxl_pci.c
@@ -1098,16 +1098,10 @@ out:
     pci_add_dm_done(egc, pas, rc); /* must be last */
 }
 
-static void pci_add_qmp_device_add(libxl__egc *egc, pci_add_state *pas)
+libxl__json_object *libxl__device_pci_get_qmp_json(libxl__gc *gc,
+                                                   libxl_device_pci *pci)
 {
-    STATE_AO_GC(pas->aodev->ao);
     libxl__json_object *args = NULL;
-    int rc;
-
-    /* Convenience aliases */
-    libxl_domid domid = pas->domid;
-    libxl_device_pci *pci = &pas->pci;
-    libxl__ev_qmp *const qmp = &pas->qmp;
 
     libxl__qmp_param_add_string(gc, &args, "driver",
                                 "xen-pci-passthrough");
@@ -1134,11 +1128,30 @@ static void pci_add_qmp_device_add(libxl__egc *egc, 
pci_add_state *pas)
     if (pci->permissive)
         libxl__qmp_param_add_bool(gc, &args, "permissive", true);
 
+    return args;
+}
+
+static void pci_add_qmp_device_add(libxl__egc *egc, pci_add_state *pas)
+{
+    STATE_AO_GC(pas->aodev->ao);
+    libxl__json_object *args = NULL;
+    int rc = 0;
+
+    /* Convenience aliases */
+    libxl_domid domid = pas->domid;
+    libxl_device_pci *pci = &pas->pci;
+    libxl__ev_qmp *const qmp = &pas->qmp;
+
+    args = libxl__device_pci_get_qmp_json(gc, pci);
+
     qmp->ao = pas->aodev->ao;
     qmp->domid = domid;
     qmp->payload_fd = -1;
     qmp->callback = pci_add_qmp_device_add_cb;
-    rc = libxl__ev_qmp_send(egc, qmp, "device_add", args);
+    if (pci->hotplug)
+        rc = libxl__ev_qmp_send(egc, qmp, "device_add", args);
+    else
+        pci_add_qmp_device_add_cb(egc, qmp, NULL, 0);
     if (rc) goto out;
     return;
 
@@ -1509,7 +1522,7 @@ int libxl_device_pci_add(libxl_ctx *ctx, uint32_t domid,
     return AO_INPROGRESS;
 }
 
-static bool libxl_pci_assignable(libxl_ctx *ctx, libxl_device_pci *pci)
+bool libxl_pci_assignable(libxl_ctx *ctx, libxl_device_pci *pci)
 {
     libxl_device_pci *pcis;
     int num;
@@ -1820,6 +1833,14 @@ static void do_pci_remove(libxl__egc *egc, 
pci_remove_state *prs)
     libxl_domain_type type = libxl__domain_type(gc, domid);
     libxl_device_pci *pci = &prs->pci;
     int rc, num;
+
+    /* Passthrough'd device has been passed to Qemu command line so there is
+     * no need to remove it via QMP */
+    if (!pci->hotplug) {
+        pci_remove_done(egc, prs, 0);
+        return;
+    }
+
     pcis = libxl_device_pci_list(ctx, domid, &num);
     if (!pcis) {
         rc = ERROR_FAIL;
-- 
2.53.0



--
Thierry Escande | Vates XCP-ng Developer

XCP-ng & Xen Orchestra - Vates solutions

web: https://vates.tech