From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-x242.google.com (mail-pl0-x242.google.com [IPv6:2607:f8b0:400e:c01::242]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 3C1C2225264B9 for ; Wed, 4 Apr 2018 22:53:16 -0700 (PDT) Received: by mail-pl0-x242.google.com with SMTP id b6-v6so15711688pla.11 for ; Wed, 04 Apr 2018 22:53:16 -0700 (PDT) Date: Thu, 5 Apr 2018 15:53:07 +1000 From: Balbir Singh Subject: Re: [RESEND 2/3] powerpc/memcpy: Add memcpy_mcsafe for pmem Message-ID: <20180405155307.49f748f3@gmail.com> In-Reply-To: <20180405150405.5b902b41@roar.ozlabs.ibm.com> References: <20180404231943.29581-1-bsingharora@gmail.com> <20180404231943.29581-3-bsingharora@gmail.com> <20180405095755.58b3891f@roar.ozlabs.ibm.com> <20180405150405.5b902b41@roar.ozlabs.ibm.com> MIME-Version: 1.0 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Nicholas Piggin Cc: "Luck, Tony" , Matthew Wilcox , Michael Ellerman , linux-nvdimm , linuxppc-dev , Christoph Hellwig List-ID: On Thu, 5 Apr 2018 15:04:05 +1000 Nicholas Piggin wrote: > On Wed, 4 Apr 2018 20:00:52 -0700 > Dan Williams wrote: > > > [ adding Matthew, Christoph, and Tony ] > > > > On Wed, Apr 4, 2018 at 4:57 PM, Nicholas Piggin wrote: > > > On Thu, 5 Apr 2018 09:19:42 +1000 > > > Balbir Singh wrote: > > > > > >> The pmem infrastructure uses memcpy_mcsafe in the pmem > > >> layer so as to convert machine check excpetions into > > >> a return value on failure in case a machine check > > >> exception is encoutered during the memcpy. > > >> > > >> This patch largely borrows from the copyuser_power7 > > >> logic and does not add the VMX optimizations, largely > > >> to keep the patch simple. If needed those optimizations > > >> can be folded in. > > > > > > So memcpy_mcsafe doesn't return number of bytes copied? > > > Huh, well that makes it simple. > > > > Well, not in current kernels, but we need to add that support or > > remove the direct call to copy_to_iter() in fs/dax.c. I'm looking > > right now to add "bytes remaining" support to the x86 memcpy_mcsafe(), > > but for copy_to_user we also need to handle bytes remaining for write > > faults. That fix is hopefully something that can land in an early > > 4.17-rc, but it won't be ready for -rc1. > > I wonder if the powerpc implementation should just go straight to > counting bytes. Backporting to this interface would be trivial, but > it would just mean there's only one variant of the code to support. > That's up to Balbir though. > I'm thinking about it, I wonder what "bytes remaining" mean in pmem context in the context of a machine check exception. Also, do we want to be byte accurate or cache-line accurate for the bytes remaining? The former is much easier than the latter :) I'd rather implement the existing interface and port/support the new interface as it becomes available Balbir Singh. _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-x241.google.com (mail-pl0-x241.google.com [IPv6:2607:f8b0:400e:c01::241]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 40GsSZ1zlVzF1sg for ; Thu, 5 Apr 2018 15:53:18 +1000 (AEST) Received: by mail-pl0-x241.google.com with SMTP id s10-v6so15724476plp.0 for ; Wed, 04 Apr 2018 22:53:18 -0700 (PDT) Date: Thu, 5 Apr 2018 15:53:07 +1000 From: Balbir Singh To: Nicholas Piggin Cc: Dan Williams , Michael Ellerman , linuxppc-dev , linux-nvdimm , Christoph Hellwig , Matthew Wilcox , "Luck, Tony" Subject: Re: [RESEND 2/3] powerpc/memcpy: Add memcpy_mcsafe for pmem Message-ID: <20180405155307.49f748f3@gmail.com> In-Reply-To: <20180405150405.5b902b41@roar.ozlabs.ibm.com> References: <20180404231943.29581-1-bsingharora@gmail.com> <20180404231943.29581-3-bsingharora@gmail.com> <20180405095755.58b3891f@roar.ozlabs.ibm.com> <20180405150405.5b902b41@roar.ozlabs.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 5 Apr 2018 15:04:05 +1000 Nicholas Piggin wrote: > On Wed, 4 Apr 2018 20:00:52 -0700 > Dan Williams wrote: > > > [ adding Matthew, Christoph, and Tony ] > > > > On Wed, Apr 4, 2018 at 4:57 PM, Nicholas Piggin wrote: > > > On Thu, 5 Apr 2018 09:19:42 +1000 > > > Balbir Singh wrote: > > > > > >> The pmem infrastructure uses memcpy_mcsafe in the pmem > > >> layer so as to convert machine check excpetions into > > >> a return value on failure in case a machine check > > >> exception is encoutered during the memcpy. > > >> > > >> This patch largely borrows from the copyuser_power7 > > >> logic and does not add the VMX optimizations, largely > > >> to keep the patch simple. If needed those optimizations > > >> can be folded in. > > > > > > So memcpy_mcsafe doesn't return number of bytes copied? > > > Huh, well that makes it simple. > > > > Well, not in current kernels, but we need to add that support or > > remove the direct call to copy_to_iter() in fs/dax.c. I'm looking > > right now to add "bytes remaining" support to the x86 memcpy_mcsafe(), > > but for copy_to_user we also need to handle bytes remaining for write > > faults. That fix is hopefully something that can land in an early > > 4.17-rc, but it won't be ready for -rc1. > > I wonder if the powerpc implementation should just go straight to > counting bytes. Backporting to this interface would be trivial, but > it would just mean there's only one variant of the code to support. > That's up to Balbir though. > I'm thinking about it, I wonder what "bytes remaining" mean in pmem context in the context of a machine check exception. Also, do we want to be byte accurate or cache-line accurate for the bytes remaining? The former is much easier than the latter :) I'd rather implement the existing interface and port/support the new interface as it becomes available Balbir Singh.