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Fri, 15 Jan 2021 08:51:59 -0800 (PST) Received: from bobo.ibm.com ([124.170.13.62]) by smtp.gmail.com with ESMTPSA id u1sm8455477pjr.51.2021.01.15.08.51.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Jan 2021 08:51:59 -0800 (PST) From: Nicholas Piggin To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH v6 28/39] powerpc/64s/hash: improve context tracking of hash faults Date: Sat, 16 Jan 2021 02:50:01 +1000 Message-Id: <20210115165012.1260253-29-npiggin@gmail.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20210115165012.1260253-1-npiggin@gmail.com> References: <20210115165012.1260253-1-npiggin@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Nicholas Piggin Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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 --- arch/powerpc/include/asm/bug.h | 1 + arch/powerpc/mm/book3s64/hash_utils.c | 7 ++++--- arch/powerpc/mm/fault.c | 30 +++++++++++++++++++++------ 3 files changed, 29 insertions(+), 9 deletions(-) diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h index c10ae0a9bbaf..d1635ffbb179 100644 --- a/arch/powerpc/include/asm/bug.h +++ b/arch/powerpc/include/asm/bug.h @@ -112,6 +112,7 @@ struct pt_regs; long do_page_fault(struct pt_regs *); +long hash__do_page_fault(struct pt_regs *); void bad_page_fault(struct pt_regs *, int); void __bad_page_fault(struct pt_regs *regs, int sig); void do_bad_page_fault_segv(struct pt_regs *regs); diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c index 824fcb2627e4..b7b78aeea3eb 100644 --- a/arch/powerpc/mm/book3s64/hash_utils.c +++ b/arch/powerpc/mm/book3s64/hash_utils.c @@ -1289,7 +1289,6 @@ int hash_page_mm(struct mm_struct *mm, unsigned long ea, unsigned long flags) { bool is_thp; - enum ctx_state prev_state = exception_enter(); pgd_t *pgdir; unsigned long vsid; pte_t *ptep; @@ -1491,7 +1490,6 @@ int hash_page_mm(struct mm_struct *mm, unsigned long ea, DBG_LOW(" -> rc=%d\n", rc); bail: - exception_exit(prev_state); return rc; } EXPORT_SYMBOL_GPL(hash_page_mm); @@ -1515,6 +1513,7 @@ EXPORT_SYMBOL_GPL(hash_page); DEFINE_INTERRUPT_HANDLER_RET(__do_hash_fault) { + enum ctx_state prev_state = exception_enter(); unsigned long ea = regs->dar; unsigned long dsisr = regs->dsisr; unsigned long access = _PAGE_PRESENT | _PAGE_READ; @@ -1563,6 +1562,8 @@ DEFINE_INTERRUPT_HANDLER_RET(__do_hash_fault) err = 0; } + exception_exit(prev_state); + return err; } @@ -1599,7 +1600,7 @@ DEFINE_INTERRUPT_HANDLER_RAW(do_hash_fault) err = __do_hash_fault(regs); if (err) { page_fault: - err = do_page_fault(regs); + err = hash__do_page_fault(regs); } return err; diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index eef7281507f9..620ff623b2c6 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; @@ -537,15 +537,13 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address, 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) { - 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 (unlikely(err)) { const struct exception_table_entry *entry; @@ -560,12 +558,32 @@ DEFINE_INTERRUPT_HANDLER_RET(do_page_fault) } } + 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); + 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 -- 2.23.0