[Xen-changelog] [xen master] x86: fix instruction emulator test's xgetbv constraints

[patchbot@xxxxxxx]

commit 09c856316d67045d170679b6980f34348e4c402f
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Apr 16 18:18:35 2014 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Apr 16 18:18:35 2014 +0200

    x86: fix instruction emulator test's xgetbv constraints
    
    The "A" constraint, while documented up to gcc 4.5 as "The a and d
    registers, as a pair (for instructions that return half the result in
    one and half in the other)," never really behaved that (natural) way,
    but always meant (and is now also documented so) %eax _or_ %edx (%rax
    _or_ %rdx on x86-64) unless the operand was wide enough to require both
    (i.e. more than 32 bits on ix86 and more than 64 bits on x86-64).
    
    Interestingly something internal to the compiler changed between 4.4
    and 4.5 to actually expose the difference - up to gcc 4.4 I was unable
    to construct a case where, when only the low half of the result is
    actually looked at, the result would be considered to be in %edx/%rdx
    (and %eax/%rax would be treated as unmodified by the instruction).
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Keir Fraser <keir@xxxxxxx>
    Tested-by: Don Slutz <dslutz@xxxxxxxxxxx>
---
 tools/tests/x86_emulator/test_x86_emulator.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/tests/x86_emulator/test_x86_emulator.c 
b/tools/tests/x86_emulator/test_x86_emulator.c
index 17b674b..0a00d5a 100644
--- a/tools/tests/x86_emulator/test_x86_emulator.c
+++ b/tools/tests/x86_emulator/test_x86_emulator.c
@@ -102,11 +102,11 @@ static int cpuid(
 
 static inline uint64_t xgetbv(uint32_t xcr)
 {
-    uint64_t res;
+    uint32_t lo, hi;
 
-    asm ( ".byte 0x0f, 0x01, 0xd0" : "=A" (res) : "c" (xcr) );
+    asm ( ".byte 0x0f, 0x01, 0xd0" : "=a" (lo), "=d" (hi) : "c" (xcr) );
 
-    return res;
+    return ((uint64_t)hi << 32) | lo;
 }
 
 #define cpu_has_avx ({ \
--
generated by git-patchbot for /home/xen/git/xen.git#master

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