On 06.06.14 18:27, Aneesh Kumar K.V wrote:
Alexander Graf <ag...@suse.de> writes:

On 05.06.14 14:08, Aneesh Kumar K.V wrote:
virtual time base register is a per VM, per cpu register that needs
to be saved and restored on vm exit and entry. Writing to VTB is not
allowed in the privileged mode.

Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
For some reason BUG() doesn't always trigger the "execution stops here"
logic in gcc. So I've squashed this patch into yours.


Alex


diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 3e7085d..99de6ad 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -1206,6 +1206,7 @@ static inline unsigned long mfvtb (void)
        * capture that.
        */
       BUG();
+    return 0;
   }

   #ifdef __powerpc64__
you can then drop the include header change. ie,

#include <asm/bug.h>

Yeah, things are even worse than I thought. I've eventually squashed the following in. a NOP'ed mfspr() won't keep the branch from blr'ing, so we'd never hit the BUG() anyway.


Alex

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 1f34ef7..c8f3381 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -25,7 +25,6 @@
 #ifdef CONFIG_8xx
 #include <asm/reg_8xx.h>
 #endif /* CONFIG_8xx */
-#include <asm/bug.h>

 #define MSR_SF_LG      63              /* Enable 64 bit mode */
#define MSR_ISF_LG 61 /* Interrupt 64b mode valid on 630 */
@@ -1210,12 +1209,6 @@ static inline unsigned long mfvtb (void)
        if (cpu_has_feature(CPU_FTR_ARCH_207S))
                return mfspr(SPRN_VTB);
 #endif
-       /*
-        * The above mfspr will be a no-op on anything before Power8
-        * That can result in random values returned. We need to
-        * capture that.
-        */
-       BUG();
        return 0;
 }


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