From: Kefeng Wang <wangkefeng.wang@huawei.com>
Date: Wed, 3 Apr 2024 08:38:03 +0000 (+0800)
Subject: riscv: mm: accelerate pagefault when badaccess
X-Git-Tag: io_uring-6.10-20240523~37^2~198
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=cd1c91b8548372ced64a01eb6eef67b539506238;p=linux-block.git

riscv: mm: accelerate pagefault when badaccess

The access_error() of vma already checked under per-VMA lock, if it is a
bad access, directly handle error, no need to retry with mmap_lock again.
Since the page faut is handled under per-VMA lock, count it as a vma lock
event with VMA_LOCK_SUCCESS.

[wangkefeng.wang@huawei.com: use `cause' rather than SIGSEGV, per Alexandre]
  Link: https://lkml.kernel.org/r/ac978061-ce1a-40a4-8b0a-61883b42bea7@huawei.com
Link: https://lkml.kernel.org/r/20240403083805.1818160-6-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Tested-by: Alexandre Ghiti <alexghiti@rivosinc.com
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index 3ba1d4dde5dd..5224f3733802 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -292,7 +292,10 @@ void handle_page_fault(struct pt_regs *regs)
 
 	if (unlikely(access_error(cause, vma))) {
 		vma_end_read(vma);
-		goto lock_mmap;
+		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
+		tsk->thread.bad_cause = cause;
+		bad_area_nosemaphore(regs, SEGV_ACCERR, addr);
+		return;
 	}
 
 	fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);