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[1/2] powerpc/32s: Do kuep_lock() and kuep_unlock() in assembly

Message ID 37dd7289fc63ef7decdec43ee74fb242d1ac6571.1625816918.git.christophe.leroy@csgroup.eu (mailing list archive)
State Superseded
Headers show
Series [1/2] powerpc/32s: Do kuep_lock() and kuep_unlock() in assembly | expand
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Context Check Description
snowpatch_ozlabs/apply_patch success Successfully applied on branch powerpc/merge (8b3ae5772c2771c21ffcda36203f8f507ebc6fc0)
snowpatch_ozlabs/checkpatch warning total: 2 errors, 1 warnings, 0 checks, 239 lines checked
snowpatch_ozlabs/needsstable success Patch has no Fixes tags

Commit Message

Christophe Leroy July 9, 2021, 7:48 a.m. UTC 
When interrupt and syscall entries where converted to C, KUEP locking
and unlocking was also converted. It improved performance by unrolling
the loop, and allowed easily implementing boot time deactivation of
KUEP.

However, null_syscall selftest shows that KUEP is still heavy
(361 cycles with KUEP, 210 cycles without).

A way to improve more is to group 'mtsr's together, instead of
repeating 'addi' + 'mtsr' several times.

In order to do that, more registers need to be available. In C, GCC
will always be able to provide the requested number of registers, but
at the cost of saving some data on the stack, which is counter
performant here.

So let's do it in assembly, when we have full control of which
register can be used. It also has the advantage of locking earlier
and unlocking later and it helps GCC generating less tricky code.
The only drawback is to make boot time deactivation less straight
forward and require 'hand' instruction patching.

In syscall entry, there are only 4 registers availables, so
group 'mtsr's by 4.

In interrupt entry, syscall exit and interrupt exist, we can group
by 6, which means 2 groups for a typical config with 12 user segments.

With this change, null_syscall selftest reports 334 cycles. Without
the change it was 361 cycles, that's an 7% reduction.

For the time being, capability to deactive at boot time is disabled.
It will be re-enabled in following patch.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/book3s/32/kup.h      | 16 ---
 arch/powerpc/include/asm/book3s/32/mmu-hash.h | 98 ++++++++++++++++++-
 arch/powerpc/include/asm/interrupt.h          |  6 +-
 arch/powerpc/include/asm/kup.h                |  5 -
 arch/powerpc/kernel/entry_32.S                | 26 +++++
 arch/powerpc/kernel/head_32.h                 |  2 +
 arch/powerpc/kernel/interrupt.c               |  3 -
 arch/powerpc/mm/book3s32/kuep.c               |  7 +-
 8 files changed, 133 insertions(+), 30 deletions(-)

Comments

kernel test robot July 9, 2021, 12:55 p.m. UTC | #1 
Hi Christophe,

I love your patch! Yet something to improve:

[auto build test ERROR on powerpc/next]
[also build test ERROR on next-20210709]
[cannot apply to v5.13]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Christophe-Leroy/powerpc-32s-Do-kuep_lock-and-kuep_unlock-in-assembly/20210709-155049
base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: powerpc-randconfig-r032-20210709 (attached as .config)
compiler: powerpc-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/8f55557e42a793db98e4e60b7c65d47a6c5a4b62
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Christophe-Leroy/powerpc-32s-Do-kuep_lock-and-kuep_unlock-in-assembly/20210709-155049
        git checkout 8f55557e42a793db98e4e60b7c65d47a6c5a4b62
        # save the attached .config to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross O=build_dir ARCH=powerpc SHELL=/bin/bash arch/powerpc/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   arch/powerpc/kernel/entry_32.S: Assembler messages:
>> arch/powerpc/kernel/entry_32.S:110: Error: unrecognized opcode: `update_user_segments_by_4'
>> arch/powerpc/kernel/entry_32.S:132: Error: unrecognized opcode: `update_user_segments_by_6'
   arch/powerpc/kernel/entry_32.S:300: Error: unrecognized opcode: `update_user_segments_by_6'


vim +110 arch/powerpc/kernel/entry_32.S

    85	
    86		.globl	transfer_to_syscall
    87	transfer_to_syscall:
    88		stw	r11, GPR1(r1)
    89		stw	r11, 0(r1)
    90		mflr	r12
    91		stw	r12, _LINK(r1)
    92	#if defined(CONFIG_BOOKE) || defined(CONFIG_40x)
    93		rlwinm	r9,r9,0,14,12		/* clear MSR_WE (necessary?) */
    94	#endif
    95		lis	r12,STACK_FRAME_REGS_MARKER@ha /* exception frame marker */
    96		SAVE_GPR(2, r1)
    97		addi	r12,r12,STACK_FRAME_REGS_MARKER@l
    98		stw	r9,_MSR(r1)
    99		li	r2, INTERRUPT_SYSCALL
   100		stw	r12,8(r1)
   101		stw	r2,_TRAP(r1)
   102		SAVE_GPR(0, r1)
   103		SAVE_4GPRS(3, r1)
   104		SAVE_2GPRS(7, r1)
   105		addi	r2,r10,-THREAD
   106	#ifdef CONFIG_PPC_KUEP
   107		mfsr    r9,0
   108		rlwinm  r9,r9,0,8,3
   109		oris    r9,r9,SR_NX@h
 > 110		update_user_segments_by_4 r9, r10, r11, r12
   111	#endif
   112		SAVE_NVGPRS(r1)
   113	
   114		/* Calling convention has r9 = orig r0, r10 = regs */
   115		addi	r10,r1,STACK_FRAME_OVERHEAD
   116		mr	r9,r0
   117		bl	system_call_exception
   118	
   119	ret_from_syscall:
   120		addi    r4,r1,STACK_FRAME_OVERHEAD
   121		li	r5,0
   122		bl	syscall_exit_prepare
   123	#ifdef CONFIG_PPC_47x
   124		lis	r4,icache_44x_need_flush@ha
   125		lwz	r5,icache_44x_need_flush@l(r4)
   126		cmplwi	cr0,r5,0
   127		bne-	2f
   128	#endif /* CONFIG_PPC_47x */
   129	#ifdef CONFIG_PPC_KUEP
   130		mfsr    r7,0
   131		rlwinm  r7,r7,0,8,2
 > 132		update_user_segments_by_6 r7, r8, r9, r10, r11, r12
   133	#endif
   134		lwz	r4,_LINK(r1)
   135		lwz	r5,_CCR(r1)
   136		mtlr	r4
   137		lwz	r7,_NIP(r1)
   138		lwz	r8,_MSR(r1)
   139		cmpwi	r3,0
   140		lwz	r3,GPR3(r1)
   141	syscall_exit_finish:
   142		mtspr	SPRN_SRR0,r7
   143		mtspr	SPRN_SRR1,r8
   144	
   145		bne	3f
   146		mtcr	r5
   147	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
diff mbox series

Patch

diff --git a/arch/powerpc/include/asm/book3s/32/kup.h b/arch/powerpc/include/asm/book3s/32/kup.h
index 64201125a287..2e0e87cf7d7a 100644
--- a/arch/powerpc/include/asm/book3s/32/kup.h
+++ b/arch/powerpc/include/asm/book3s/32/kup.h
@@ -22,22 +22,6 @@  static __always_inline bool kuep_is_disabled(void)
 	return !IS_ENABLED(CONFIG_PPC_KUEP) || static_branch_unlikely(&disable_kuep_key);
 }
 
-static inline void kuep_lock(void)
-{
-	if (kuep_is_disabled())
-		return;
-
-	update_user_segments(mfsr(0) | SR_NX);
-}
-
-static inline void kuep_unlock(void)
-{
-	if (kuep_is_disabled())
-		return;
-
-	update_user_segments(mfsr(0) & ~SR_NX);
-}
-
 #ifdef CONFIG_PPC_KUAP
 
 #include <linux/sched.h>
diff --git a/arch/powerpc/include/asm/book3s/32/mmu-hash.h b/arch/powerpc/include/asm/book3s/32/mmu-hash.h
index f5be185cbdf8..e6c90802de03 100644
--- a/arch/powerpc/include/asm/book3s/32/mmu-hash.h
+++ b/arch/powerpc/include/asm/book3s/32/mmu-hash.h
@@ -64,7 +64,103 @@  struct ppc_bat {
 #define SR_KP	0x20000000	/* User key */
 #define SR_KS	0x40000000	/* Supervisor key */
 
-#ifndef __ASSEMBLY__
+#ifdef __ASSEMBLY__
+
+#include <asm/asm-offsets.h>
+
+.macro uus_addi sr reg1 reg2 imm
+	.if NUM_USER_SEGMENTS > \sr
+	addi	\reg1,\reg2,\imm
+	.endif
+.endm
+
+.macro uus_mtsr sr reg1
+	.if NUM_USER_SEGMENTS > \sr
+	mtsr	\sr, \reg1
+	.endif
+.endm
+
+.macro update_user_segments_by_4 tmp1 tmp2 tmp3 tmp4
+	uus_addi	1, \tmp2, \tmp1, 0x111
+	uus_addi	2, \tmp3, \tmp1, 0x222
+	uus_addi	3, \tmp4, \tmp1, 0x333
+
+	uus_mtsr	0, \tmp1
+	uus_mtsr	1, \tmp2
+	uus_mtsr	2, \tmp3
+	uus_mtsr	3, \tmp4
+
+	uus_addi	4, \tmp1, \tmp1, 0x444
+	uus_addi	5, \tmp2, \tmp2, 0x444
+	uus_addi	6, \tmp3, \tmp3, 0x444
+	uus_addi	7, \tmp4, \tmp4, 0x444
+
+	uus_mtsr	4, \tmp1
+	uus_mtsr	5, \tmp2
+	uus_mtsr	6, \tmp3
+	uus_mtsr	7, \tmp4
+
+	uus_addi	8, \tmp1, \tmp1, 0x444
+	uus_addi	9, \tmp2, \tmp2, 0x444
+	uus_addi	10, \tmp3, \tmp3, 0x444
+	uus_addi	11, \tmp4, \tmp4, 0x444
+
+	uus_mtsr	8, \tmp1
+	uus_mtsr	9, \tmp2
+	uus_mtsr	10, \tmp3
+	uus_mtsr	11, \tmp4
+
+	uus_addi	12, \tmp1, \tmp1, 0x444
+	uus_addi	13, \tmp2, \tmp2, 0x444
+	uus_addi	14, \tmp3, \tmp3, 0x444
+	uus_addi	15, \tmp4, \tmp4, 0x444
+
+	uus_mtsr	12, \tmp1
+	uus_mtsr	13, \tmp2
+	uus_mtsr	14, \tmp3
+	uus_mtsr	15, \tmp4
+.endm
+
+.macro update_user_segments_by_6 tmp1 tmp2 tmp3 tmp4 tmp5 tmp6
+	uus_addi	1, \tmp2, \tmp1, 0x111
+	uus_addi	2, \tmp3, \tmp1, 0x222
+	uus_addi	3, \tmp4, \tmp1, 0x333
+	uus_addi	4, \tmp5, \tmp1, 0x444
+	uus_addi	5, \tmp6, \tmp1, 0x555
+
+	uus_mtsr	0, \tmp1
+	uus_mtsr	1, \tmp2
+	uus_mtsr	2, \tmp3
+	uus_mtsr	3, \tmp4
+	uus_mtsr	4, \tmp5
+	uus_mtsr	5, \tmp6
+
+	uus_addi	6, \tmp1, \tmp1, 0x666
+	uus_addi	7, \tmp2, \tmp2, 0x666
+	uus_addi	8, \tmp3, \tmp3, 0x666
+	uus_addi	9, \tmp4, \tmp4, 0x666
+	uus_addi	10, \tmp5, \tmp5, 0x666
+	uus_addi	11, \tmp6, \tmp6, 0x666
+
+	uus_mtsr	6, \tmp1
+	uus_mtsr	7, \tmp2
+	uus_mtsr	8, \tmp3
+	uus_mtsr	9, \tmp4
+	uus_mtsr	10, \tmp5
+	uus_mtsr	11, \tmp6
+
+	uus_addi	12, \tmp1, \tmp1, 0x666
+	uus_addi	13, \tmp2, \tmp2, 0x666
+	uus_addi	14, \tmp3, \tmp3, 0x666
+	uus_addi	15, \tmp4, \tmp4, 0x666
+
+	uus_mtsr	12, \tmp1
+	uus_mtsr	13, \tmp2
+	uus_mtsr	14, \tmp3
+	uus_mtsr	15, \tmp4
+.endm
+
+#else
 
 /*
  * This macro defines the mapping from contexts to VSIDs (virtual
diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
index d4bdf7d274ac..d4349ca37084 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -139,12 +139,10 @@  static inline void interrupt_enter_prepare(struct pt_regs *regs, struct interrup
 	if (!arch_irq_disabled_regs(regs))
 		trace_hardirqs_off();
 
-	if (user_mode(regs)) {
-		kuep_lock();
+	if (user_mode(regs))
 		account_cpu_user_entry();
-	} else {
+	else
 		kuap_save_and_lock(regs);
-	}
 #endif
 
 #ifdef CONFIG_PPC64
diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h
index 1df763002726..34ff86e3686e 100644
--- a/arch/powerpc/include/asm/kup.h
+++ b/arch/powerpc/include/asm/kup.h
@@ -38,11 +38,6 @@  void setup_kuep(bool disabled);
 static inline void setup_kuep(bool disabled) { }
 #endif /* CONFIG_PPC_KUEP */
 
-#ifndef CONFIG_PPC_BOOK3S_32
-static inline void kuep_lock(void) { }
-static inline void kuep_unlock(void) { }
-#endif
-
 #ifdef CONFIG_PPC_KUAP
 void setup_kuap(bool disabled);
 #else
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 0273a1349006..84b51a387e95 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -52,6 +52,16 @@ 
 #if defined(CONFIG_PPC_BOOK3S_32) || defined(CONFIG_E500)
 	.globl	prepare_transfer_to_handler
 prepare_transfer_to_handler:
+#ifdef CONFIG_PPC_KUEP
+	beq	1f
+
+	mfsr    r4,0
+	rlwinm  r4,r4,0,8,3
+	oris    r4,r4,SR_NX@h
+	update_user_segments_by_6 r4, r5, r6, r7, r8, r9
+	blr
+1:
+#endif
 	/* if from kernel, check interrupted DOZE/NAP mode */
 	lwz	r12,TI_LOCAL_FLAGS(r2)
 	mtcrf	0x01,r12
@@ -93,6 +103,12 @@  transfer_to_syscall:
 	SAVE_4GPRS(3, r1)
 	SAVE_2GPRS(7, r1)
 	addi	r2,r10,-THREAD
+#ifdef CONFIG_PPC_KUEP
+	mfsr    r9,0
+	rlwinm  r9,r9,0,8,3
+	oris    r9,r9,SR_NX@h
+	update_user_segments_by_4 r9, r10, r11, r12
+#endif
 	SAVE_NVGPRS(r1)
 
 	/* Calling convention has r9 = orig r0, r10 = regs */
@@ -110,6 +126,11 @@  ret_from_syscall:
 	cmplwi	cr0,r5,0
 	bne-	2f
 #endif /* CONFIG_PPC_47x */
+#ifdef CONFIG_PPC_KUEP
+	mfsr    r7,0
+	rlwinm  r7,r7,0,8,2
+	update_user_segments_by_6 r7, r8, r9, r10, r11, r12
+#endif
 	lwz	r4,_LINK(r1)
 	lwz	r5,_CCR(r1)
 	mtlr	r4
@@ -273,6 +294,11 @@  interrupt_return:
 	beq	.Lkernel_interrupt_return
 	bl	interrupt_exit_user_prepare
 	cmpwi	r3,0
+#ifdef CONFIG_PPC_KUEP
+	mfsr    r7,0
+	rlwinm  r7,r7,0,8,2
+	update_user_segments_by_6 r7, r8, r9, r10, r11, r12
+#endif
 	bne-	.Lrestore_nvgprs
 
 .Lfast_user_interrupt_return:
diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h
index 6b1ec9e3541b..4df20fa73504 100644
--- a/arch/powerpc/kernel/head_32.h
+++ b/arch/powerpc/kernel/head_32.h
@@ -134,7 +134,9 @@  _ASM_NOKPROBE_SYMBOL(\name\()_virt)
 .macro prepare_transfer_to_handler
 #ifdef CONFIG_PPC_BOOK3S_32
 	andi.	r12,r9,MSR_PR
+#ifndef CONFIG_PPC_KUEP
 	bne	777f
+#endif
 	bl	prepare_transfer_to_handler
 777:
 #endif
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index 21bbd615ca41..cd6139003776 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -81,8 +81,6 @@  notrace long system_call_exception(long r3, long r4, long r5,
 {
 	syscall_fn f;
 
-	kuep_lock();
-
 	regs->orig_gpr3 = r3;
 
 	if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
@@ -365,7 +363,6 @@  interrupt_exit_user_prepare_main(unsigned long ret, struct pt_regs *regs)
 
 	/* Restore user access locks last */
 	kuap_user_restore(regs);
-	kuep_unlock();
 
 	return ret;
 }
diff --git a/arch/powerpc/mm/book3s32/kuep.c b/arch/powerpc/mm/book3s32/kuep.c
index c20733d6e02c..45c9967f9aef 100644
--- a/arch/powerpc/mm/book3s32/kuep.c
+++ b/arch/powerpc/mm/book3s32/kuep.c
@@ -7,8 +7,13 @@  struct static_key_false disable_kuep_key;
 
 void setup_kuep(bool disabled)
 {
+	if (disabled) {
+		pr_info("KUEP cannot be disabled for the time being\n");
+		disabled = false;
+	}
+
 	if (!disabled)
-		kuep_lock();
+		update_user_segments(mfsr(0) | SR_NX);
 
 	if (smp_processor_id() != boot_cpuid)
 		return;