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powerpc/mm: Pre-filter SRR1 bits before do_page_fault()

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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>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Benjamin Herrenschmidt 2017-07-19 14:49:24 +10:00 committed by Michael Ellerman
parent 7afad422ac
commit c433ec0455
3 changed files with 5 additions and 15 deletions
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2
arch/powerpc/kernel/head_32.S
View File

@ -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 */

4
arch/powerpc/kernel/head_8xx.S
View File

@ -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:

14
arch/powerpc/mm/fault.c
View File

@ -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 */