Re: next-20170217 boot on POWER8 LPAR : WARNING @kernel/jump_label.c:287

[Jason Baron]

On 02/20/2017 10:05 PM, Sachin Sant wrote:
> > On 20-Feb-2017, at 8:27 PM, Jason Baron <jbaron@xxxxxxxxxx
> > <mailto:jbaron@xxxxxxxxxx>> wrote:
> >
> > Hi,
> >
> > On 02/19/2017 09:07 AM, Sachin Sant wrote:
> > > While booting next-20170217 on a POWER8 LPAR following
> > > warning is displayed.
> > >
> > > Reverting the following commit helps boot cleanly.
> > > commit 3821fd35b5 :  jump_label: Reduce the size of struct static_key
> > >
> > > [   11.393008] ------------[ cut here ]------------
> > > [   11.393031] WARNING: CPU: 5 PID: 2890 at kernel/jump_label.c:287
> > > static_key_set_entries.isra.10+0x3c/0x50
> >
> > Thanks for the report. So this is saying that the jump_entry table is
> > not at least 4-byte aligned. I wonder if this fixes it up?
>
> Yes. With this patch the warning is gone.

Hi,

Thanks for testing. We probably need something like the following to 
make sure we don't hit this on other arches. Steve - I will send 4 
separate patches for this to get arch maintainers' acks for this?

Thanks,

-Jason

diff --git a/arch/arm/include/asm/jump_label.h 
b/arch/arm/include/asm/jump_label.h
index 34f7b6980d21..9720c2f1850b 100644
--- a/arch/arm/include/asm/jump_label.h
+++ b/arch/arm/include/asm/jump_label.h
@@ -13,6 +13,7 @@ static __always_inline bool arch_static_branch(struct 
static_key *key, bool bran
        asm_volatile_goto("1:\n\t"
                 WASM(nop) "\n\t"
                 ".pushsection __jump_table,  \"aw\"\n\t"
+                ".balign 4 \n\t"
                 ".word 1b, %l[l_yes], %c0\n\t"
                 ".popsection\n\t"
                 : :  "i" (&((char *)key)[branch]) :  : l_yes);
@@ -27,6 +28,7 @@ static __always_inline bool 
arch_static_branch_jump(struct static_key *key, bool
        asm_volatile_goto("1:\n\t"
                 WASM(b) " %l[l_yes]\n\t"
                 ".pushsection __jump_table,  \"aw\"\n\t"
+                ".balign 4 \n\t"
                 ".word 1b, %l[l_yes], %c0\n\t"
                 ".popsection\n\t"
                 : :  "i" (&((char *)key)[branch]) :  : l_yes);
diff --git a/arch/mips/include/asm/jump_label.h 
b/arch/mips/include/asm/jump_label.h
index e77672539e8e..51ce97dda3cc 100644
--- a/arch/mips/include/asm/jump_label.h
+++ b/arch/mips/include/asm/jump_label.h
@@ -31,6 +31,7 @@ static __always_inline bool arch_static_branch(struct 
static_key *key, bool bran
        asm_volatile_goto("1:\t" NOP_INSN "\n\t"
                "nop\n\t"
                ".pushsection __jump_table,  \"aw\"\n\t"
+               ".balign 4 \n\t"
                WORD_INSN " 1b, %l[l_yes], %0\n\t"
                ".popsection\n\t"
                : :  "i" (&((char *)key)[branch]) : : l_yes);
@@ -45,6 +46,7 @@ static __always_inline bool 
arch_static_branch_jump(struct static_key *key, bool
        asm_volatile_goto("1:\tj %l[l_yes]\n\t"
                "nop\n\t"
                ".pushsection __jump_table,  \"aw\"\n\t"
+               ".balign 4 \n\t"
                WORD_INSN " 1b, %l[l_yes], %0\n\t"
                ".popsection\n\t"
                : :  "i" (&((char *)key)[branch]) : : l_yes);
diff --git a/arch/powerpc/include/asm/jump_label.h 
b/arch/powerpc/include/asm/jump_label.h
index 9a287e0ac8b1..f870a85bac46 100644
--- a/arch/powerpc/include/asm/jump_label.h
+++ b/arch/powerpc/include/asm/jump_label.h
@@ -24,6 +24,7 @@ static __always_inline bool arch_static_branch(struct 
static_key *key, bool bran
        asm_volatile_goto("1:\n\t"
                 "nop # arch_static_branch\n\t"
                 ".pushsection __jump_table,  \"aw\"\n\t"
+                ".balign 4 \n\t"
                 JUMP_ENTRY_TYPE "1b, %l[l_yes], %c0\n\t"
                 ".popsection \n\t"
                 : :  "i" (&((char *)key)[branch]) : : l_yes);
@@ -38,6 +39,7 @@ static __always_inline bool 
arch_static_branch_jump(struct static_key *key, bool
        asm_volatile_goto("1:\n\t"
                 "b %l[l_yes] # arch_static_branch_jump\n\t"
                 ".pushsection __jump_table,  \"aw\"\n\t"
+                ".balign 4 \n\t"
                 JUMP_ENTRY_TYPE "1b, %l[l_yes], %c0\n\t"
                 ".popsection \n\t"
                 : :  "i" (&((char *)key)[branch]) : : l_yes);
@@ -63,6 +65,7 @@ struct jump_entry {
 #define ARCH_STATIC_BRANCH(LABEL, KEY)         \
 1098:  nop;                                    \
        .pushsection __jump_table, "aw";        \
+       .balign 4;                              \
        FTR_ENTRY_LONG 1098b, LABEL, KEY;       \
        .popsection
 #endif
diff --git a/arch/tile/include/asm/jump_label.h 
b/arch/tile/include/asm/jump_label.h
index cde7573f397b..c9f6125c41ef 100644
--- a/arch/tile/include/asm/jump_label.h
+++ b/arch/tile/include/asm/jump_label.h
@@ -25,6 +25,7 @@ static __always_inline bool arch_static_branch(struct 
static_key *key,
        asm_volatile_goto("1:\n\t"
                "nop" "\n\t"
                ".pushsection __jump_table,  \"aw\"\n\t"
+               ".balign 4 \n\t"
                ".quad 1b, %l[l_yes], %0 + %1 \n\t"
                ".popsection\n\t"
                : :  "i" (key), "i" (branch) : : l_yes);
@@ -39,6 +40,7 @@ static __always_inline bool 
arch_static_branch_jump(struct static_key *key,
        asm_volatile_goto("1:\n\t"
                "j %l[l_yes]" "\n\t"
                ".pushsection __jump_table,  \"aw\"\n\t"
+               ".balign 4 \n\t"
                ".quad 1b, %l[l_yes], %0 + %1 \n\t"
                ".popsection\n\t"
                : :  "i" (key), "i" (branch) : : l_yes);