From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9E20453A7 for ; Wed, 3 Apr 2024 18:32:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712169151; cv=none; b=SpDK8bapnD7Y3OKP3TmXhhy6Oj319wzxSiyRiOZNJ38fgoKTGcmoeIdFkNZg7tRSHHMDQuBAZLqpsxqVC9Ns4EMOhUPY9XdY1+oYiW8p/6Jpsfguuoi/T6D0RhKMUEv4PX2QJs6U5Wwwsvd39h7uMQdymbVrlqgntXegPhLIvMk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712169151; c=relaxed/simple; bh=oyirPimBJOA8FFF3zedLDMmcJbW6rsNP/gocNStF39o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ON+Gw6rqDz1N2ugu5DaPl8UlYlJ8jx9vH1RZP6pxrCfz3DvFLKBntdEUn4rDU3Zzisb17MXlfrzrF6aJMlw8B4zGYENV3eQJ3y2Ic9m3CL+rKs++vNavUN380X6kffgy5zR7Dlv8UShokBpzH87k9ELFz2C00kqzwSkgs3FtGtI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 881B8C433C7; Wed, 3 Apr 2024 18:32:27 +0000 (UTC) Date: Wed, 3 Apr 2024 19:32:25 +0100 From: Catalin Marinas To: Kefeng Wang Cc: akpm@linux-foundation.org, Russell King , Will Deacon , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexander Gordeev , Gerald Schaefer , Dave Hansen , Andy Lutomirski , Peter Zijlstra , x86@kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, surenb@google.com Subject: Re: [PATCH 2/7] arm64: mm: accelerate pagefault when VM_FAULT_BADACCESS Message-ID: References: <20240402075142.196265-1-wangkefeng.wang@huawei.com> <20240402075142.196265-3-wangkefeng.wang@huawei.com> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240402075142.196265-3-wangkefeng.wang@huawei.com> On Tue, Apr 02, 2024 at 03:51:37PM +0800, Kefeng Wang wrote: > The vm_flags of vma already checked under per-VMA lock, if it is a > bad access, directly set fault to VM_FAULT_BADACCESS and handle error, > no need to lock_mm_and_find_vma() and check vm_flags again, the latency > time reduce 34% in lmbench 'lat_sig -P 1 prot lat_sig'. > > Signed-off-by: Kefeng Wang > --- > arch/arm64/mm/fault.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index 9bb9f395351a..405f9aa831bd 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -572,7 +572,9 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, > > if (!(vma->vm_flags & vm_flags)) { > vma_end_read(vma); > - goto lock_mmap; > + fault = VM_FAULT_BADACCESS; > + count_vm_vma_lock_event(VMA_LOCK_SUCCESS); > + goto done; > } > fault = handle_mm_fault(vma, addr, mm_flags | FAULT_FLAG_VMA_LOCK, regs); > if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED))) I think this makes sense. A concurrent modification of vma->vm_flags (e.g. mprotect()) would do a vma_start_write(), so no need to recheck again with the mmap lock held. Reviewed-by: Catalin Marinas