[Qemu-devel] [PATCH] kvm: Fix enable_cap helpers on older gcc

[Alexander Graf <agraf@suse.de>]

Commit 40f1ee27aa1 introduced handy helpers for enable_cap calls on
vcpu and vm level. Unfortunately some older gcc versions (4.7.1, 4.6)
seem to choke on signedness detection in inline created variables:

target-ppc/kvm.c: In function 'kvmppc_booke_watchdog_enable':
target-ppc/kvm.c:1302:21: error: comparison of unsigned expression < 0 is always false [-Werror=type-limits]
target-ppc/kvm.c: In function 'kvmppc_set_papr':
target-ppc/kvm.c:1504:21: error: comparison of unsigned expression < 0 is always false [-Werror=type-limits]

We can easily work around this by not doing a compare with 0, but instead
shift all values up by one. The resulting binary should look the same, as
all those ARRAY_SIZE values are compile time statically optimized.

This patch fixes compile errors on some of my systems.

Signed-off-by: Alexander Graf <agraf@suse.de>
---
 include/sysemu/kvm.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index 192fe89..989c261 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -302,9 +302,9 @@ int kvm_check_extension(KVMState *s, unsigned int extension);
         };                                                           \
         uint64_t args_tmp[] = { __VA_ARGS__ };                       \
         int i;                                                       \
-        for (i = 0; i < ARRAY_SIZE(args_tmp) &&                      \
-                     i < ARRAY_SIZE(cap.args); i++) {                \
-            cap.args[i] = args_tmp[i];                               \
+        for (i = 1; i < (MIN(ARRAY_SIZE(args_tmp),                   \
+                             ARRAY_SIZE(cap.args)) + 1); i++) {      \
+            cap.args[i - 1] = args_tmp[i - 1];                       \
         }                                                            \
         kvm_vm_ioctl(s, KVM_ENABLE_CAP, &cap);                       \
     })
@@ -317,9 +317,9 @@ int kvm_check_extension(KVMState *s, unsigned int extension);
         };                                                           \
         uint64_t args_tmp[] = { __VA_ARGS__ };                       \
         int i;                                                       \
-        for (i = 0; i < ARRAY_SIZE(args_tmp) &&                      \
-                     i < ARRAY_SIZE(cap.args); i++) {                \
-            cap.args[i] = args_tmp[i];                               \
+        for (i = 1; i < (MIN(ARRAY_SIZE(args_tmp),                   \
+                             ARRAY_SIZE(cap.args)) + 1); i++) {      \
+            cap.args[i - 1] = args_tmp[i - 1];                       \
         }                                                            \
         kvm_vcpu_ioctl(cpu, KVM_ENABLE_CAP, &cap);                   \
     })
-- 
1.8.1.4