Re: [PATCH 4/5] Powerpc/hw-breakpoint: Optimize disable path
From: Michael Neuling <hidden>
Date: 2019-06-18 06:52:25
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On Tue, 2019-06-18 at 09:57 +0530, Ravi Bangoria wrote:
Directly setting dawr and dawrx with 0 should be enough to disable watchpoint. No need to reset individual bits in variable and then set in hw.
This seems like a pointless optimisation to me. I'm all for adding more code/complexity if it buys us some performance, but I can't imagine this is a fast path (nor have you stated any performance benefits). Mikey
quoted hunk ↗ jump to hunk
Signed-off-by: Ravi Bangoria <redacted> --- arch/powerpc/include/asm/hw_breakpoint.h | 3 ++- arch/powerpc/kernel/process.c | 12 ++++++++++++ 2 files changed, 14 insertions(+), 1 deletion(-)diff --git a/arch/powerpc/include/asm/hw_breakpoint.hb/arch/powerpc/include/asm/hw_breakpoint.h index 78202d5fb13a..8acbbdd4a2d5 100644--- a/arch/powerpc/include/asm/hw_breakpoint.h +++ b/arch/powerpc/include/asm/hw_breakpoint.h@@ -19,6 +19,7 @@ struct arch_hw_breakpoint { /* Note: Don't change the the first 6 bits below as they are in the sameorder * as the dabr and dabrx. */ +#define HW_BRK_TYPE_DISABLE 0x00 #define HW_BRK_TYPE_READ 0x01 #define HW_BRK_TYPE_WRITE 0x02 #define HW_BRK_TYPE_TRANSLATE 0x04@@ -68,7 +69,7 @@ static inline void hw_breakpoint_disable(void) struct arch_hw_breakpoint brk; brk.address = 0; - brk.type = 0; + brk.type = HW_BRK_TYPE_DISABLE; brk.len = 0; if (ppc_breakpoint_available()) __set_breakpoint(&brk);diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index f002d2ffff86..265fac9fb3a4 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c@@ -793,10 +793,22 @@ static inline int set_dabr(struct arch_hw_breakpoint*brk) return __set_dabr(dabr, dabrx); } +static int disable_dawr(void) +{ + if (ppc_md.set_dawr) + return ppc_md.set_dawr(0, 0); + + mtspr(SPRN_DAWRX, 0); + return 0; +} + int set_dawr(struct arch_hw_breakpoint *brk) { unsigned long dawr, dawrx, mrd; + if (brk->type == HW_BRK_TYPE_DISABLE) + return disable_dawr(); + dawr = brk->address; dawrx = (brk->type & HW_BRK_TYPE_RDWR) << (63 - 58);