summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorSamuel Holland <samuel@sholland.org>2023-08-04 11:51:59 +0300
committerLey Foon Tan <leyfoon.tan@starfivetech.com>2023-12-04 06:00:16 +0300
commit74be6dc880b7a953ba068e6e5210d29b20f5e531 (patch)
treefe734eff0376f9993254734c690e6b7ec712a568
parentc26ff90eca925e92374da6feb6f583581b92bd3c (diff)
downloadlinux-74be6dc880b7a953ba068e6e5210d29b20f5e531.tar.xz
riscv: Fix build with CONFIG_CC_OPTIMIZE_FOR_SIZE=y
[ upstream commit 0b1d60d6dd9e2e867cc6e4277d73ea5a7ff2d4d0 ] commit 8eb060e10185 ("arch/riscv: add Zihintpause support") broke building with CONFIG_CC_OPTIMIZE_FOR_SIZE enabled (gcc 11.1.0): CC arch/riscv/kernel/vdso/vgettimeofday.o In file included from <command-line>: ./arch/riscv/include/asm/jump_label.h: In function 'cpu_relax': ././include/linux/compiler_types.h:285:33: warning: 'asm' operand 0 probably does not match constraints 285 | #define asm_volatile_goto(x...) asm goto(x) | ^~~ ./arch/riscv/include/asm/jump_label.h:41:9: note: in expansion of macro 'asm_volatile_goto' 41 | asm_volatile_goto( | ^~~~~~~~~~~~~~~~~ ././include/linux/compiler_types.h:285:33: error: impossible constraint in 'asm' 285 | #define asm_volatile_goto(x...) asm goto(x) | ^~~ ./arch/riscv/include/asm/jump_label.h:41:9: note: in expansion of macro 'asm_volatile_goto' 41 | asm_volatile_goto( | ^~~~~~~~~~~~~~~~~ make[1]: *** [scripts/Makefile.build:249: arch/riscv/kernel/vdso/vgettimeofday.o] Error 1 make: *** [arch/riscv/Makefile:128: vdso_prepare] Error 2 Having a static branch in cpu_relax() is problematic because that function is widely inlined, including in some quite complex functions like in the VDSO. A quick measurement shows this static branch is responsible by itself for around 40% of the jump table. Drop the static branch, which ends up being the same number of instructions anyway. If Zihintpause is supported, we trade the nop from the static branch for a div. If Zihintpause is unsupported, we trade the jump from the static branch for (what gets interpreted as) a nop. Fixes: 8eb060e10185 ("arch/riscv: add Zihintpause support") Signed-off-by: Samuel Holland <samuel@sholland.org> Reviewed-by: Conor Dooley <conor.dooley@microchip.com> Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
-rw-r--r--arch/riscv/include/asm/hwcap.h3
-rw-r--r--arch/riscv/include/asm/vdso/processor.h25
2 files changed, 10 insertions, 18 deletions
diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index b22525290073..404349f49101 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -69,7 +69,6 @@ enum riscv_isa_ext_id {
*/
enum riscv_isa_ext_key {
RISCV_ISA_EXT_KEY_FPU, /* For 'F' and 'D' */
- RISCV_ISA_EXT_KEY_ZIHINTPAUSE,
RISCV_ISA_EXT_KEY_SVINVAL,
RISCV_ISA_EXT_KEY_MAX,
};
@@ -90,8 +89,6 @@ static __always_inline int riscv_isa_ext2key(int num)
return RISCV_ISA_EXT_KEY_FPU;
case RISCV_ISA_EXT_d:
return RISCV_ISA_EXT_KEY_FPU;
- case RISCV_ISA_EXT_ZIHINTPAUSE:
- return RISCV_ISA_EXT_KEY_ZIHINTPAUSE;
case RISCV_ISA_EXT_SVINVAL:
return RISCV_ISA_EXT_KEY_SVINVAL;
default:
diff --git a/arch/riscv/include/asm/vdso/processor.h b/arch/riscv/include/asm/vdso/processor.h
index fa70cfe507aa..c25399711b07 100644
--- a/arch/riscv/include/asm/vdso/processor.h
+++ b/arch/riscv/include/asm/vdso/processor.h
@@ -4,30 +4,25 @@
#ifndef __ASSEMBLY__
-#include <linux/jump_label.h>
#include <asm/barrier.h>
-#include <asm/hwcap.h>
static inline void cpu_relax(void)
{
- if (!static_branch_likely(&riscv_isa_ext_keys[RISCV_ISA_EXT_KEY_ZIHINTPAUSE])) {
#ifdef __riscv_muldiv
- int dummy;
- /* In lieu of a halt instruction, induce a long-latency stall. */
- __asm__ __volatile__ ("div %0, %0, zero" : "=r" (dummy));
+ int dummy;
+ /* In lieu of a halt instruction, induce a long-latency stall. */
+ __asm__ __volatile__ ("div %0, %0, zero" : "=r" (dummy));
#endif
- } else {
- /*
- * Reduce instruction retirement.
- * This assumes the PC changes.
- */
+ /*
+ * Reduce instruction retirement.
+ * This assumes the PC changes.
+ */
#ifdef CONFIG_TOOLCHAIN_HAS_ZIHINTPAUSE
- __asm__ __volatile__ ("pause");
+ __asm__ __volatile__ ("pause");
#else
- /* Encoding of the pause instruction */
- __asm__ __volatile__ (".4byte 0x100000F");
+ /* Encoding of the pause instruction */
+ __asm__ __volatile__ (".4byte 0x100000F");
#endif
- }
barrier();
}