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commit d7c4d59b51929451a047e0fb62b229c67d6dd7be
Author: Jason Andryuk <jandryuk@gmail.com>
AuthorDate: Thu Apr 25 09:47:52 2024 +0200
Commit: Jan Beulich <jbeulich@suse.com>
CommitDate: Thu Apr 25 09:47:52 2024 +0200

libxl: Support blktap with HVM device model

blktap exposes disks over UNIX socket Network Block Device (NBD).
Modify libxl__device_disk_find_local_path() to provide back the
QEMU-formatted NBD path. This allows tapdisk to be used for booting an
HVM.

Use the nbd+unix:/// format specified by the protocol at
https://github.com/NetworkBlockDevice/nbd/blob/master/doc/uri.md

Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
---
tools/libs/light/libxl_disk.c | 18 ++++++++++++++----
tools/libs/light/libxl_dm.c | 1 -
2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/tools/libs/light/libxl_disk.c b/tools/libs/light/libxl_disk.c
index fa7856f28c..1f1e5c6567 100644
--- a/tools/libs/light/libxl_disk.c
+++ b/tools/libs/light/libxl_disk.c
@@ -1361,7 +1361,8 @@ char *libxl__device_disk_find_local_path(libxl__gc *gc,
* If the format isn't raw and / or we're using a script, then see
* if the script has written a path to the "cooked" node
*/
- if (disk->script && guest_domid != INVALID_DOMID) {
+ if ((disk->script && guest_domid != INVALID_DOMID) ||
+ disk->backend == LIBXL_DISK_BACKEND_TAP) {
libxl__device device;
char *be_path, *pdpath;
int rc;
@@ -1381,10 +1382,19 @@ char *libxl__device_disk_find_local_path(libxl__gc *gc,
LOGD(DEBUG, guest_domid, "Attempting to read node %s", pdpath);
path = libxl__xs_read(gc, XBT_NULL, pdpath);

- if (path)
+ if (path) {
LOGD(DEBUG, guest_domid, "Accessing cooked block device %s", path);
- else
- LOGD(DEBUG, guest_domid, "No physical-device-path, can't access locally.");
+
+ /* tapdisk exposes disks locally over UNIX socket NBD. */
+ if (disk->backend == LIBXL_DISK_BACKEND_TAP) {
+ path = libxl__sprintf(gc, "nbd+unix:///?socket=%s", path);
+ LOGD(DEBUG, guest_domid,
+ "Directly accessing local TAP target %s", path);
+ }
+ } else {
+ LOGD(DEBUG, guest_domid,
+ "No physical-device-path, can't access locally.");
+ }

goto out;
}
diff --git a/tools/libs/light/libxl_dm.c b/tools/libs/light/libxl_dm.c
index 567ae1ec7e..ff8ddeec9a 100644
--- a/tools/libs/light/libxl_dm.c
+++ b/tools/libs/light/libxl_dm.c
@@ -1915,7 +1915,6 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
continue;
}

- assert(disks[i].backend != LIBXL_DISK_BACKEND_TAP);
target_path = libxl__device_disk_find_local_path(gc,
guest_domid, &disks[i], true);

--
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