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([2001:df0:0:200c:e490:6dca:29ba:7b4b]) by smtp.gmail.com with ESMTPSA id y62sm8703674pfg.88.2021.08.15.12.17.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 15 Aug 2021 12:17:20 -0700 (PDT) Subject: Re: RFC: remove set_fs for m68k To: Christoph Hellwig Cc: Andreas Schwab , Geert Uytterhoeven , Greg Ungerer , linux-m68k@lists.linux-m68k.org, Linus Torvalds References: <3acb1a9e-9133-50d4-a642-98d7046d6d4f@gmail.com> <65a95ae0-4734-68ce-ef71-7491b5534718@gmail.com> <8f470389-fe8a-90b0-19a5-68f85526b30e@gmail.com> <20210721170529.GA14550@lst.de> <20210723051126.GA31274@lst.de> <8884e940-22e8-72a5-e9ec-f9b2628b6ef4@gmail.com> <251aa093-047a-b37c-4e88-d543c6fa8bc6@gmail.com> <20210815074236.GA23777@lst.de> From: Michael Schmitz Message-ID: <63c35a20-3eec-1825-fa18-5df28f5b6eaa@gmail.com> Date: Mon, 16 Aug 2021 07:17:15 +1200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210815074236.GA23777@lst.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-m68k@vger.kernel.org Hi Christoph, On 15/08/21 7:42 pm, Christoph Hellwig wrote: > Hi Michael, > > after your last mail I went back and looked very closely at the > set_fs removal and your debug patches below. And one hunk stands out: > >> static inline void flush_tlb_page(struct vm_area_struct *vma, unsigned long addr) >> { >> - if (vma->vm_mm == current->active_mm) >> + if (vma->vm_mm == current->active_mm) { >> + unsigned long old_fc = force_user_fc_begin(); >> __flush_tlb_one(addr); >> + force_user_fc_end(old_fc); >> + } > This is the only old user of force_uaccess_begin, and the only one > where this patch adds back a DFC/SFC access where there was none at > at all with the set_fs removal. So I'd be curious if you just add this > hunk (plus the supporting infrastructure) on top of my tree for now to > see if there were some side effects of the instructions that were > important, be that seralization, timing or anything else. Would it be acceptable to add this on top of the probe040/do_040writeback1 patch that I'm currently testing? Cheers,     Michael