From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f41.google.com (mail-oi0-f41.google.com [209.85.218.41]) by kanga.kvack.org (Postfix) with ESMTP id DAF3D6B009A for ; Fri, 29 May 2015 16:29:39 -0400 (EDT) Received: by oifu123 with SMTP id u123so65156108oif.1 for ; Fri, 29 May 2015 13:29:39 -0700 (PDT) Received: from g2t2352.austin.hp.com (g2t2352.austin.hp.com. [15.217.128.51]) by mx.google.com with ESMTPS id o87si4203993oik.97.2015.05.29.13.29.37 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 29 May 2015 13:29:38 -0700 (PDT) Message-ID: <1432930202.23540.87.camel@misato.fc.hp.com> Subject: Re: [PATCH v10 12/12] drivers/block/pmem: Map NVDIMM with ioremap_wt() From: Toshi Kani Date: Fri, 29 May 2015 14:10:02 -0600 In-Reply-To: References: <1432739944-22633-1-git-send-email-toshi.kani@hp.com> <1432739944-22633-13-git-send-email-toshi.kani@hp.com> <20150529091129.GC31435@pd.tnic> <1432911782.23540.55.camel@misato.fc.hp.com> <1432924340.23540.78.camel@misato.fc.hp.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams Cc: Borislav Petkov , Ross Zwisler , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , Andrew Morton , Arnd Bergmann , linux-mm@kvack.org, "linux-kernel@vger.kernel.org" , X86 ML , "linux-nvdimm@lists.01.org" , Juergen Gross , Stefan Bader , Andy Lutomirski , Henrique de Moraes Holschuh , Yigal Korman , Konrad Rzeszutek Wilk , "Elliott, Robert (Server Storage)" , Luis Rodriguez , Christoph Hellwig , Matthew Wilcox On Fri, 2015-05-29 at 12:34 -0700, Dan Williams wrote: > On Fri, May 29, 2015 at 11:32 AM, Toshi Kani wrote: > > On Fri, 2015-05-29 at 11:19 -0700, Dan Williams wrote: > >> On Fri, May 29, 2015 at 8:03 AM, Toshi Kani wrote: > >> > On Fri, 2015-05-29 at 07:43 -0700, Dan Williams wrote: > >> >> On Fri, May 29, 2015 at 2:11 AM, Borislav Petkov wrote: > >> >> > On Wed, May 27, 2015 at 09:19:04AM -0600, Toshi Kani wrote: > >> >> >> The pmem driver maps NVDIMM with ioremap_nocache() as we cannot > > : > >> >> >> - pmem->virt_addr = ioremap_nocache(pmem->phys_addr, pmem->size); > >> >> >> + pmem->virt_addr = ioremap_wt(pmem->phys_addr, pmem->size); > >> >> >> if (!pmem->virt_addr) > >> >> >> goto out_release_region; > >> >> > > >> >> > Dan, Ross, what about this one? > >> >> > > >> >> > ACK to pick it up as a temporary solution? > >> >> > >> >> I see that is_new_memtype_allowed() is updated to disallow some > >> >> combinations, but the manual seems to imply any mixing of memory types > >> >> is unsupported. Which worries me even in the current code where we > >> >> have uncached mappings in the driver, and potentially cached DAX > >> >> mappings handed out to userspace. > >> > > >> > is_new_memtype_allowed() is not to allow some combinations of mixing of > >> > memory types. When it is allowed, the requested type of ioremap_xxx() > >> > is changed to match with the existing map type, so that mixing of memory > >> > types does not happen. > >> > >> Yes, but now if the caller was expecting one memory type and gets > >> another one that is something I think the driver would want to know. > >> At a minimum I don't think we want to get emails about pmem driver > >> performance problems when someone's platform is silently degrading WB > >> to UC for example. > > > > The pmem driver creates an ioremap map to an NVDIMM range first. So, > > there will be no conflict at this point, unless there is a conflicting > > driver claiming the same NVDIMM range. > > Hmm, I thought it would be WB due to this comment in is_new_memtype_allowed() > > /* > * PAT type is always WB for untracked ranges, so no need to check. > */ This comment applies to the ISA range, where ioremap() does not create any mapping to, i.e. untracked. You can ignore this comment for NVDIMM. Thanks, -Toshi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org