[PATCH 02/24] powerpc/mm: Pre-filter SRR1 bits before do_page_fault()
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: 2017-07-19 04:50:22
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
By filtering the relevant SRR1 bits in the assembly rather than in do_page_fault() itself, we avoid a conditional branch (since we already come from different path for data and instruction faults). This will allow more simplifications later Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> --- arch/powerpc/kernel/head_32.S | 2 +- arch/powerpc/kernel/head_8xx.S | 4 ++-- arch/powerpc/mm/fault.c | 14 ++------------ 3 files changed, 5 insertions(+), 15 deletions(-)
diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index a5301248b098..f11d1cd6e314 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S@@ -409,7 +409,7 @@ InstructionAccess: mr r4,r12 /* SRR0 is fault address */ bl hash_page 1: mr r4,r12 - mr r5,r9 + andis. r5,r9,0x4820 /* Filter relevant SRR1 bits */ EXC_XFER_LITE(0x400, handle_page_fault) /* External interrupt */
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index c032fe8c2d26..da3afa2c1658 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S@@ -569,8 +569,8 @@ _ENTRY(DTLBMiss_jmp) InstructionTLBError: EXCEPTION_PROLOG mr r4,r12 - mr r5,r9 - andis. r10,r5,0x4000 + andis. r5,r9,0x4820 /* Filter relevant SRR1 bits */ + andis. r10,r9,0x4000 beq+ 1f tlbie r4 itlbie:
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index faddc87d0205..f04bc9f6b134 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c@@ -203,23 +203,13 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address, unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; int code = SEGV_MAPERR; int is_write = 0; - int trap = TRAP(regs); - int is_exec = trap == 0x400; + int is_exec = TRAP(regs) == 0x400; int is_user = user_mode(regs); int fault; int rc = 0, store_update_sp = 0; #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) - /* - * Fortunately the bit assignments in SRR1 for an instruction - * fault and DSISR for a data fault are mostly the same for the - * bits we are interested in. But there are some bits which - * indicate errors in DSISR but can validly be set in SRR1. - */ - if (is_exec) - error_code &= 0x48200000; - else - is_write = error_code & DSISR_ISSTORE; + is_write = error_code & DSISR_ISSTORE; #else is_write = error_code & ESR_DST; #endif /* CONFIG_4xx || CONFIG_BOOKE */
--
2.13.3