[Xen-devel] [PATCH] libxl: fix libxl_domain_need_memory after 899433f149d

[Wei Liu <wei.liu2@xxxxxxxxxx>]

After 899433f149d libxl needs to know the content of d_config to
determine which QEMU is used. The code is changed such that
libxl__domain_set_device_model needs to be called before
libxl__domain_build_info_setdefault.

This is fine for libxl code, but it is problematic for
libxl_domain_need_memory, which is the only public API that takes a
build_info. To avoid break its users, provide a compatibility setting
inside that function.

Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Olaf Hering <olaf@xxxxxxxxx>
Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>

Please test.
---
 tools/libxl/libxl_mem.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/tools/libxl/libxl_mem.c b/tools/libxl/libxl_mem.c
index 448a2af8fd..fe1f9c2ff8 100644
--- a/tools/libxl/libxl_mem.c
+++ b/tools/libxl/libxl_mem.c
@@ -457,6 +457,24 @@ int libxl_domain_need_memory(libxl_ctx *ctx,
     libxl_domain_build_info_init(b_info);
     libxl_domain_build_info_copy(ctx, b_info, b_info_in);
 
+    /*
+     * It has become a requirement that to figure out which QEMU to
+     * use, libxl will need to peek d_config's content. The code has
+     * been changed such that one will need to call
+     * libxl__domain_set_device_model before calling
+     * libxl__domain_build_info_setdefault inside libxl.
+     *
+     * This (problematic) public API is the only one which takes a
+     * b_info, imposing the same requirement on the users of this
+     * public API will break them.
+     *
+     * Provide a compatibility setting for this function. The
+     * calculation doesn't really care which QEMU is set here, so we
+     * go with the upstream default.
+     */
+    if (!b_info->device_model_version)
+       b_info->device_model_version = LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN;
+
     rc = libxl__domain_build_info_setdefault(gc, b_info);
     if (rc) goto out;
 
-- 
2.20.1


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