[Xen-devel] [PATCH] xen: Fix build with older versions of GCC following e34bc403c3

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

GCCs of at least 4.4 and earlier do not tollerate the initialisiation of the
$VENDOR_cpu_dev structures, because of c_ident becoming an anonymous union.

Instead of using an anonymous union, reintepret c_ident[] in its CPUID form
just in get_cpu_vendor().

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

RFC, as I don't have easy access to a compiler which causes this to fail in
the first place.
---
 xen/arch/x86/cpu/common.c | 7 +++++--
 xen/arch/x86/cpu/cpu.h    | 8 +-------
 2 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index d17a2ee..7d6d024 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -163,8 +163,11 @@ int get_cpu_vendor(uint32_t b, uint32_t c, uint32_t d, 
enum get_cpu_vendor mode)
 
        for (i = 0; i < X86_VENDOR_NUM; i++) {
                if (cpu_devs[i]) {
-                       if (cpu_devs[i]->b == b && cpu_devs[i]->c == c &&
-                           cpu_devs[i]->d == d) {
+                       struct {
+                               uint32_t b, d, c;
+                       } *ptr = (void *)cpu_devs[i]->c_ident;
+
+                       if (ptr->b == b && ptr->c == c && ptr->d == d) {
                                if (mode == gcv_host)
                                        this_cpu = cpu_devs[i];
                                return i;
diff --git a/xen/arch/x86/cpu/cpu.h b/xen/arch/x86/cpu/cpu.h
index 5a7905c..3eeebe3 100644
--- a/xen/arch/x86/cpu/cpu.h
+++ b/xen/arch/x86/cpu/cpu.h
@@ -1,13 +1,7 @@
 /* attempt to consolidate cpu attributes */
 struct cpu_dev {
        char    c_vendor[8];
-
-       union {
-               char    c_ident[13];
-               struct {
-                       uint32_t b, d, c;
-               };
-       };
+       char    c_ident[13];
 
        void            (*c_early_init)(struct cpuinfo_x86 *c);
        void            (*c_init)(struct cpuinfo_x86 * c);
-- 
2.1.4


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