From a008f8f9fd67ffb13d906ef4ea6235a3d62dfdb6 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Sat, 30 Jan 2021 23:08:41 +1000 Subject: powerpc/64s/hash: improve context tracking of hash faults This moves the 64s/hash context tracking from hash_page_mm() to __do_hash_fault(), so it's no longer called by OCXL / SPU accelerators, which was certainly the wrong thing to be doing, because those callers are not low level interrupt handlers, so should have entered a kernel context tracking already. Then remain in kernel context for the duration of the fault, rather than enter/exit for the hash fault then enter/exit for the page fault, which is pointless. Even still, calling exception_enter/exit in __do_hash_fault seems questionable because that's touching per-cpu variables, tracing, etc., which might have been interrupted by this hash fault or themselves cause hash faults. But maybe I miss something because hash_page_mm very deliberately calls trace_hash_fault too, for example. So for now go with it, it's no worse than before, in this regard. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210130130852.2952424-32-npiggin@gmail.com --- arch/powerpc/mm/fault.c | 39 ++++++++++++++++++++++++++++----------- 1 file changed, 28 insertions(+), 11 deletions(-) (limited to 'arch/powerpc/mm/fault.c') diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index 8552ab6c008b..9c4220efc20f 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -387,7 +387,7 @@ static void sanity_check_fault(bool is_write, bool is_user, * The return value is 0 if the fault was handled, or the signal * number if this is a kernel fault that can't be handled here. */ -static int __do_page_fault(struct pt_regs *regs, unsigned long address, +static int ___do_page_fault(struct pt_regs *regs, unsigned long address, unsigned long error_code) { struct vm_area_struct * vma; @@ -537,36 +537,53 @@ retry: return 0; } -NOKPROBE_SYMBOL(__do_page_fault); +NOKPROBE_SYMBOL(___do_page_fault); -DEFINE_INTERRUPT_HANDLER_RET(do_page_fault) +static long __do_page_fault(struct pt_regs *regs) { const struct exception_table_entry *entry; - enum ctx_state prev_state; long err; - prev_state = exception_enter(); - err = __do_page_fault(regs, regs->dar, regs->dsisr); + err = ___do_page_fault(regs, regs->dar, regs->dsisr); if (likely(!err)) - goto out; + return err; entry = search_exception_tables(regs->nip); if (likely(entry)) { instruction_pointer_set(regs, extable_fixup(entry)); - err = 0; + return 0; } else if (IS_ENABLED(CONFIG_PPC_BOOK3S_64)) { - /* 32 and 64e handle this in asm */ __bad_page_fault(regs, err); - err = 0; + return 0; + } else { + /* 32 and 64e handle the bad page fault in asm */ + return err; } +} +NOKPROBE_SYMBOL(__do_page_fault); + +DEFINE_INTERRUPT_HANDLER_RET(do_page_fault) +{ + enum ctx_state prev_state = exception_enter(); + long err; + + err = __do_page_fault(regs); -out: exception_exit(prev_state); return err; } NOKPROBE_SYMBOL(do_page_fault); +#ifdef CONFIG_PPC_BOOK3S_64 +/* Same as do_page_fault but interrupt entry has already run in do_hash_fault */ +long hash__do_page_fault(struct pt_regs *regs) +{ + return __do_page_fault(regs); +} +NOKPROBE_SYMBOL(hash__do_page_fault); +#endif + /* * bad_page_fault is called when we have a bad access from the kernel. * It is called from the DSI and ISI handlers in head.S and from some -- cgit v1.2.3