From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f47.google.com (mail-pj1-f47.google.com [209.85.216.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 86EF372 for ; Fri, 27 Aug 2021 16:42:32 +0000 (UTC) Received: by mail-pj1-f47.google.com with SMTP id g13-20020a17090a3c8d00b00196286963b9so2292245pjc.3 for ; Fri, 27 Aug 2021 09:42:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=N4ycuy1sr/uw7TD/lnGtmhJPET4O9tG56DU4s7vExRc=; b=Lvoj7e2n4w0IK4etf1iQ9jYZqI7qgmyxocAuTVCR51wfVsM28PORXBncAmMiSb0x3e gXKO8JFv+/stlktlnaeDoUlxaVoGBLZ5ZsgHPfC5/Aq9HrdpUiYRUoQ/1+/0/BxOFR+v K7gYD0KPFk0KEAAWY5Vhx9xAHx7VlgBY6t7s6nltGRqP2xWwncovu6AsRkePywesuhRH a6NpkpoQ+YZzvrV0GkepU5Ky8P3+XdqHMZ7ivVQHBsSV9uGpJEoaucRLLVjyKgiib9do nAqnLT9d4hAmtf5EmyL014xAmvelwGeJ/AcSgrD+VM20kPD9NC+fd8o/hwnX0Fn7W45d 8Xmw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=N4ycuy1sr/uw7TD/lnGtmhJPET4O9tG56DU4s7vExRc=; b=FI0X3Efte2lmJUzZ1AP5Ijc8HPFOnRMwUDMEnR6Cyr8m4uUCoN/Tz9DObm8CQSiOVn Pt8wQKYhjtM59E1Lg6c0GkqexEB6VvEBx4rlsvjAPYbkxmbXUgZ2wqnOdqomFB6JJebE dmiwMK2aby8KeUn3vCoU18J4YNtFt/uj8xZWa0zh8q4zJIrHGIXlhQJK5BbiSlm5ndsf XoFn+MQb+mASvinBrECQtkGlViDUyHipN80E2I6+1ZMXJF/L4YNVCeQjzghj0TxfVAIF UnWMC9v1vTiFqpNjiMGcD6ZydXBlcxcMIrFwOBXDB07Ryom8WNyU3fV+hh2gURA8iicx /piQ== X-Gm-Message-State: AOAM532QyzbXihzGHaJ1FpsXZ1EdcJQw11Orug2LJJgbbIdQX5huY0tH aR+Wsmc2GJEu0slVRd2LEQA3JHHZdnI4HNxeGWNsRA== X-Google-Smtp-Source: ABdhPJziK4HQfETlenNGQKDOWz+QE54n/rfbSQZA9GTYS/ZDxIcUoBcbFTG/U6SCP1KUl+Nf8+OpMuqzoNMp0yB/eFw= X-Received: by 2002:a17:902:edd0:b0:135:b351:bd5a with SMTP id q16-20020a170902edd000b00135b351bd5amr9562085plk.52.1630082551867; Fri, 27 Aug 2021 09:42:31 -0700 (PDT) Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <8b2514bb-1d4b-48bb-a666-85e6804fbac0@cn.fujitsu.com> <68169bc5-075f-8260-eedc-80fdf4b0accd@cn.fujitsu.com> <20210806014559.GM543798@ziepe.ca> <10c4bead-c778-8794-f916-80bf7ba3a56b@fujitsu.com> <20210827121034.GG1200268@ziepe.ca> In-Reply-To: From: Dan Williams Date: Fri, 27 Aug 2021 09:42:21 -0700 Message-ID: Subject: Re: RDMA/rpma + fsdax(ext4) was broken since 36f30e486d To: "Li, Zhijian" Cc: Jason Gunthorpe , "lizhijian@fujitsu.com" , "nvdimm@lists.linux.dev" , Yishai Hadas , "linux-rdma@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "yangx.jy@fujitsu.com" Content-Type: text/plain; charset="UTF-8" On Fri, Aug 27, 2021 at 6:05 AM Li, Zhijian wrote: > > > on 2021/8/27 20:10, Jason Gunthorpe wrote: > > On Fri, Aug 27, 2021 at 08:15:40AM +0000, lizhijian@fujitsu.com wrote: > >> i looked over the change-log of hmm_vma_handle_pte(), and found that before > >> 4055062 ("mm/hmm: add missing call to hmm_pte_need_fault in HMM_PFN_SPECIAL handling") > >> > >> hmm_vma_handle_pte() will not check pte_special(pte) if pte_devmap(pte) is true. > >> > >> when we reached > >> "if (pte_special(pte) && !is_zero_pfn(pte_pfn(pte))) {" > >> the pte have already presented and its pte's flag already fulfilled the request flags. > >> > >> > >> My question is that > >> Per https://01.org/blogs/dave/2020/linux-consumption-x86-page-table-bits, > >> pte_devmap(pte) and pte_special(pte) could be both true in fsdax user case, right ? > > How? what code creates that? > > > > I see: > > > > insert_pfn(): > > /* Ok, finally just insert the thing.. */ > > if (pfn_t_devmap(pfn)) > > entry = pte_mkdevmap(pfn_t_pte(pfn, prot)); > > else > > entry = pte_mkspecial(pfn_t_pte(pfn, prot)); > > > > So what code path ends up setting both bits? > > pte_mkdevmap() will set both _PAGE_SPECIAL | PAGE_DEVMAP > > 395 static inline pte_t pte_mkdevmap(pte_t pte) > 396 { > 397 return pte_set_flags(pte, _PAGE_SPECIAL|_PAGE_DEVMAP); > 398 } I can't recall why _PAGE_SPECIAL is there. I'll take a look, but I think setting _PAGE_SPECIAL in pte_mkdevmap() is overkill.