libxl: fix pci device re-assigning after domain reboot
diff mbox series

Message ID 20190626133726.29896-1-jgross@suse.com
State New, archived
Headers show
Series
  • libxl: fix pci device re-assigning after domain reboot
Related show

Commit Message

Jürgen Groß June 26, 2019, 1:37 p.m. UTC
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@suse.com>
Tested-by: Chao Gao <chao.gao@intel.com>
---
 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(-)

Comments

Roger Pau Monné June 27, 2019, 8:28 a.m. UTC | #1
On Wed, Jun 26, 2019 at 03:37:26PM +0200, Juergen Gross wrote:
> 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@suse.com>
> Tested-by: Chao Gao <chao.gao@intel.com>

Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks!

> ---
>  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 db6c0203b7..a2569102ee 100644
> --- a/tools/libxl/libxl_device.c
> +++ b/tools/libxl/libxl_device.c
> @@ -2026,6 +2026,7 @@ 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;

I think you could reduce the scope of ndevs...

>      int rc;
>  
>      *num = 0;
> @@ -2037,21 +2038,34 @@ 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) {

... by declaring it here.
Ian Jackson July 10, 2019, 6:44 p.m. UTC | #2
Roger Pau Monne writes ("Re: [Xen-devel] [PATCH] libxl: fix pci device re-assigning after domain reboot"):
> On Wed, Jun 26, 2019 at 03:37:26PM +0200, Juergen Gross wrote:
> > Signed-off-by: Juergen Gross <jgross@suse.com>
> > Tested-by: Chao Gao <chao.gao@intel.com>
> 
> Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

Committed, thanks.

Ian.
Pasi Kärkkäinen July 23, 2019, 8:57 p.m. UTC | #3
Hello,

On Wed, Jul 10, 2019 at 07:44:08PM +0100, Ian Jackson wrote:
> Roger Pau Monne writes ("Re: [Xen-devel] [PATCH] libxl: fix pci device re-assigning after domain reboot"):
> > On Wed, Jun 26, 2019 at 03:37:26PM +0200, Juergen Gross wrote:
> > > Signed-off-by: Juergen Gross <jgross@suse.com>
> > > Tested-by: Chao Gao <chao.gao@intel.com>
> > 
> > Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
> 
> Committed, thanks.
> 

I'd like to request backport of this commit to 4.12 branch.

Thanks,

-- Pasi

> Ian.
>

Patch
diff mbox series

diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index db6c0203b7..a2569102ee 100644
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -2026,6 +2026,7 @@  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;
@@ -2037,21 +2038,34 @@  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 3be5c644c1..a3102871f3 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -3707,6 +3707,7 @@  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 *,
@@ -3730,6 +3731,7 @@  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 4ec6872798..03beb865d9 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(const 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,
 );
 
 /*