[PATCH AUTOSEL 4.19 01/60] powerpc/powernv/smp: Fix spurious DBG() warning

From: Oliver O'Halloran <oohall@gmail.com>

[ Upstream commit f6bac19cf65c5be21d14a0c9684c8f560f2096dd ]

When building with W=1 we get the following warning:

 arch/powerpc/platforms/powernv/smp.c: In function ‘pnv_smp_cpu_kill_self’:
 arch/powerpc/platforms/powernv/smp.c:276:16: error: suggest braces around
 	empty body in an ‘if’ statement [-Werror=empty-body]
   276 |      cpu, srr1);
       |                ^
 cc1: all warnings being treated as errors

The full context is this block:

 if (srr1 && !generic_check_cpu_restart(cpu))
 	DBG("CPU%d Unexpected exit while offline srr1=%lx!\n",
 			cpu, srr1);

When building with DEBUG undefined DBG() expands to nothing and GCC emits
the warning due to the lack of braces around an empty statement.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200804005410.146094-2-oohall@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/powerpc/platforms/powernv/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c
index 8d49ba370c504..889c3dbec6fb9 100644
--- a/arch/powerpc/platforms/powernv/smp.c
+++ b/arch/powerpc/platforms/powernv/smp.c

@@ -47,7 +47,7 @@
 #include <asm/udbg.h>
 #define DBG(fmt...) udbg_printf(fmt)
 #else
-#define DBG(fmt...)
+#define DBG(fmt...) do { } while (0)
 #endif
 
 static void pnv_smp_setup_cpu(int cpu)

-- 
2.25.1

From: Nicholas Piggin <npiggin@gmail.com>

[ Upstream commit 66acd46080bd9e5ad2be4b0eb1d498d5145d058e ]

powerpc uses IPIs in some situations to switch a kernel thread away
from a lazy tlb mm, which is subject to the TLB flushing race
described in the changelog introducing ARCH_WANT_IRQS_OFF_ACTIVATE_MM.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200914045219.3736466-3-npiggin@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/powerpc/Kconfig                   | 1 +
 arch/powerpc/include/asm/mmu_context.h | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index f38d153d25861..0bc53f0e37c0f 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -152,6 +152,7 @@ config PPC
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_CMPXCHG_LOCKREF		if PPC64
 	select ARCH_WANT_IPC_PARSE_VERSION
+	select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
 	select ARCH_WEAK_RELEASE_ACQUIRE
 	select BINFMT_ELF
 	select BUILDTIME_EXTABLE_SORT

diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index ae953958c0f33..d93bdcaa4a469 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h

@@ -204,7 +204,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
  */
 static inline void activate_mm(struct mm_struct *prev, struct mm_struct *next)
 {
-	switch_mm(prev, next, current);
+	switch_mm_irqs_off(prev, next, current);
 }
 
 /* We don't currently use enter_lazy_tlb() for anything */

-- 
2.25.1