[Xen-changelog] [xen staging-4.12] libxl: fix pci device re-assigning after domain reboot

[patchbot@xxxxxxx]

commit dcc0bf5dec61b3dd1cc00683b5b9b5bfe0a318de
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Wed Jun 26 14:37:26 2019 +0100
Commit:     Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
CommitDate: Mon Aug 5 15:27:06 2019 +0100

    libxl: fix pci device re-assigning after domain reboot
    
    After a reboot of a guest only the first pci device configuration will
    be retrieved from Xenstore resulting in loss of any further assigned
    passed through pci devices.
    
    The main reason is that all passed through pci devices reside under a
    common root device "0" in Xenstore. So when the device list is rebuilt
    from Xenstore after a reboot the sub-devices below that root device
    need to be selected instead of using the root device number as a
    selector.
    
    Fix that by adding a new member to struct libxl_device_type which when
    set is used to get the number of devices. Add such a member for pci to
    get the correct number of pci devices instead of implying it from the
    number of pci root devices (which will always be 1).
    
    While at it fix the type of libxl__device_pci_from_xs_be() to match
    the one of the .from_xenstore member of struct libxl_device_type. This
    fixes a latent bug checking the return value of a function returning
    void.
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Tested-by: Chao Gao <chao.gao@xxxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    
    (cherry picked from commit c19434d9284e93e6f9aaec9a70f5f361adbfaba6)
    Backport-requested-by: Pasi Kärkkäinen <pasik@xxxxxx>
    Backport-requested-by: Roman Shaposhnik <roman@xxxxxxxxxx>
    Backport-requested-by: Rich Persaud <persaur@xxxxxxxxx>
---
 tools/libxl/libxl_device.c   | 24 +++++++++++++++++++-----
 tools/libxl/libxl_internal.h |  2 ++
 tools/libxl/libxl_pci.c      | 35 ++++++++++++++++++++++++++---------
 3 files changed, 47 insertions(+), 14 deletions(-)

diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index a4a8e9ac32..0bbf91bb62 100644
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -2055,6 +2055,7 @@ void *libxl__device_list(libxl__gc *gc, const struct 
libxl_device_type *dt,
     char *libxl_path;
     char **dir = NULL;
     unsigned int ndirs = 0;
+    unsigned int ndevs = 0;
     int rc;
 
     *num = 0;
@@ -2066,21 +2067,34 @@ void *libxl__device_list(libxl__gc *gc, const struct 
libxl_device_type *dt,
     dir = libxl__xs_directory(gc, XBT_NULL, libxl_path, &ndirs);
 
     if (dir && ndirs) {
-        list = libxl__malloc(NOGC, dt->dev_elem_size * ndirs);
+        if (dt->get_num) {
+            if (ndirs != 1) {
+                LOGD(ERROR, domid, "multiple entries in %s\n", libxl_path);
+                rc = ERROR_FAIL;
+                goto out;
+            }
+            rc = dt->get_num(gc, GCSPRINTF("%s/%s", libxl_path, *dir), &ndevs);
+            if (rc) goto out;
+        } else {
+            ndevs = ndirs;
+        }
+        list = libxl__malloc(NOGC, dt->dev_elem_size * ndevs);
         item = list;
 
-        while (*num < ndirs) {
+        while (*num < ndevs) {
             dt->init(item);
-            ++(*num);
 
             if (dt->from_xenstore) {
+                int nr = dt->get_num ? *num : atoi(*dir);
                 char *device_libxl_path = GCSPRINTF("%s/%s", libxl_path, *dir);
-                rc = dt->from_xenstore(gc, device_libxl_path, atoi(*dir), 
item);
+                rc = dt->from_xenstore(gc, device_libxl_path, nr, item);
                 if (rc) goto out;
             }
 
             item = (uint8_t *)item + dt->dev_elem_size;
-            ++dir;
+            ++(*num);
+            if (!dt->get_num)
+                ++dir;
         }
     }
 
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 459f9bffa8..1b48293ebf 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -3733,6 +3733,7 @@ typedef void (*device_merge_fn_t)(libxl_ctx *, void *, 
void *);
 typedef int (*device_dm_needed_fn_t)(void *, unsigned);
 typedef void (*device_update_config_fn_t)(libxl__gc *, void *, void *);
 typedef int (*device_update_devid_fn_t)(libxl__gc *, uint32_t, void *);
+typedef int (*device_get_num_fn_t)(libxl__gc *, const char *, unsigned int *);
 typedef int (*device_from_xenstore_fn_t)(libxl__gc *, const char *,
                                          libxl_devid, void *);
 typedef int (*device_set_xenstore_config_fn_t)(libxl__gc *, uint32_t, void *,
@@ -3756,6 +3757,7 @@ struct libxl_device_type {
     device_dm_needed_fn_t           dm_needed;
     device_update_config_fn_t       update_config;
     device_update_devid_fn_t        update_devid;
+    device_get_num_fn_t             get_num;
     device_from_xenstore_fn_t       from_xenstore;
     device_set_xenstore_config_fn_t set_xenstore_config;
 };
diff --git a/tools/libxl/libxl_pci.c b/tools/libxl/libxl_pci.c
index 87afa03d9e..88c324ea23 100644
--- a/tools/libxl/libxl_pci.c
+++ b/tools/libxl/libxl_pci.c
@@ -1547,12 +1547,13 @@ int libxl_device_pci_destroy(libxl_ctx *ctx, uint32_t 
domid,
     return AO_INPROGRESS;
 }
 
-static void libxl__device_pci_from_xs_be(libxl__gc *gc,
-                                         const char *be_path,
-                                         int nr, libxl_device_pci *pci)
+static int libxl__device_pci_from_xs_be(libxl__gc *gc,
+                                        const char *be_path,
+                                        libxl_devid nr, void *data)
 {
     char *s;
     unsigned int domain = 0, bus = 0, dev = 0, func = 0, vdevfn = 0;
+    libxl_device_pci *pci = data;
 
     s = libxl__xs_read(gc, XBT_NULL, GCSPRINTF("%s/dev-%d", be_path, nr));
     sscanf(s, PCI_BDF, &domain, &bus, &dev, &func);
@@ -1582,24 +1583,39 @@ static void libxl__device_pci_from_xs_be(libxl__gc *gc,
             }
         } while ((p = strtok_r(NULL, ",=", &saveptr)) != NULL);
     }
+
+    return 0;
+}
+
+static int libxl__device_pci_get_num(libxl__gc *gc, const char *be_path,
+                                     unsigned int *num)
+{
+    char *num_devs;
+    int rc = 0;
+
+    num_devs = libxl__xs_read(gc, XBT_NULL, GCSPRINTF("%s/num_devs", be_path));
+    if (!num_devs)
+        rc = ERROR_FAIL;
+    else
+        *num = atoi(num_devs);
+
+    return rc;
 }
 
 libxl_device_pci *libxl_device_pci_list(libxl_ctx *ctx, uint32_t domid, int 
*num)
 {
     GC_INIT(ctx);
-    char *be_path, *num_devs;
-    int n, i;
+    char *be_path;
+    unsigned int n, i;
     libxl_device_pci *pcidevs = NULL;
 
     *num = 0;
 
     be_path = libxl__domain_device_backend_path(gc, 0, domid, 0,
                                                 LIBXL__DEVICE_KIND_PCI);
-    num_devs = libxl__xs_read(gc, XBT_NULL, GCSPRINTF("%s/num_devs", be_path));
-    if (!num_devs)
+    if (libxl__device_pci_get_num(gc, be_path, &n))
         goto out;
 
-    n = atoi(num_devs);
     pcidevs = calloc(n, sizeof(libxl_device_pci));
 
     for (i = 0; i < n; i++)
@@ -1688,7 +1704,8 @@ static int libxl_device_pci_compare(libxl_device_pci *d1,
 #define libxl__device_pci_update_devid NULL
 
 DEFINE_DEVICE_TYPE_STRUCT_X(pcidev, pci, PCI,
-    .from_xenstore = (device_from_xenstore_fn_t)libxl__device_pci_from_xs_be,
+    .get_num = libxl__device_pci_get_num,
+    .from_xenstore = libxl__device_pci_from_xs_be,
 );
 
 /*
--
generated by git-patchbot for /home/xen/git/xen.git#staging-4.12

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