From: Dan Williams <dan.j.williams@intel.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
linux-arch@vger.kernel.org, "Kani,
Toshimitsu" <toshi.kani@hp.com>, Arnd Bergmann <arnd@arndb.de>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Russell King <rmk+kernel@arm.linux.org.uk>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2 08/25] arch: introduce memremap()
Date: Mon, 27 Jul 2015 16:26:03 -0700 [thread overview]
Message-ID: <CAPcyv4jN6jYzw11qOOR-xd_w6s5dguQSoHyvmPFSWtL9S+tz3w@mail.gmail.com> (raw)
In-Reply-To: <20150727051258.GB15836@lst.de>
On Sun, Jul 26, 2015 at 10:12 PM, Christoph Hellwig <hch@lst.de> wrote:
> On Sun, Jul 26, 2015 at 10:49:39AM -0700, Dan Williams wrote:
>> On Sun, Jul 26, 2015 at 10:25 AM, Christoph Hellwig <hch@lst.de> wrote:
>> > On Fri, Jul 24, 2015 at 10:38:42PM -0400, Dan Williams wrote:
>> >> The behavior change to return NULL on an unsupported request is reserved
>> >> for a later patch.
>> >
>> > Why?
>>
>> This is for drivers like pmem that care about the mapping type. For
>> example, if pmem can't get a cache-enabled mapping it is potentially
>> putting the write durability of the persistent media at risk.
>
> I understand that part, but the question is why the old behavior
> is retained for now and only changed later.
Oh, because all we have at this point is ioremap_cache() which
silently falls back. It's not until the introduction of
arch_memremp() where we update the arch code to break that behavior.
That said, I think it may be beneficial to allow a fallback if the
user cares. So maybe memremap() can call plain ioremap() if
MEMREMAP_STRICT is not set and none of the other mapping types are
satisfied.
WARNING: multiple messages have this Message-ID (diff)
From: Dan Williams <dan.j.williams@intel.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
linux-arch@vger.kernel.org, "Kani,
Toshimitsu" <toshi.kani@hp.com>, Arnd Bergmann <arnd@arndb.de>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Russell King <rmk+kernel@arm.linux.org.uk>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2 08/25] arch: introduce memremap()
Date: Mon, 27 Jul 2015 16:26:03 -0700 [thread overview]
Message-ID: <CAPcyv4jN6jYzw11qOOR-xd_w6s5dguQSoHyvmPFSWtL9S+tz3w@mail.gmail.com> (raw)
In-Reply-To: <20150727051258.GB15836@lst.de>
On Sun, Jul 26, 2015 at 10:12 PM, Christoph Hellwig <hch@lst.de> wrote:
> On Sun, Jul 26, 2015 at 10:49:39AM -0700, Dan Williams wrote:
>> On Sun, Jul 26, 2015 at 10:25 AM, Christoph Hellwig <hch@lst.de> wrote:
>> > On Fri, Jul 24, 2015 at 10:38:42PM -0400, Dan Williams wrote:
>> >> The behavior change to return NULL on an unsupported request is reserved
>> >> for a later patch.
>> >
>> > Why?
>>
>> This is for drivers like pmem that care about the mapping type. For
>> example, if pmem can't get a cache-enabled mapping it is potentially
>> putting the write durability of the persistent media at risk.
>
> I understand that part, but the question is why the old behavior
> is retained for now and only changed later.
Oh, because all we have at this point is ioremap_cache() which
silently falls back. It's not until the introduction of
arch_memremp() where we update the arch code to break that behavior.
That said, I think it may be beneficial to allow a fallback if the
user cares. So maybe memremap() can call plain ioremap() if
MEMREMAP_STRICT is not set and none of the other mapping types are
satisfied.
WARNING: multiple messages have this Message-ID (diff)
From: dan.j.williams@intel.com (Dan Williams)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 08/25] arch: introduce memremap()
Date: Mon, 27 Jul 2015 16:26:03 -0700 [thread overview]
Message-ID: <CAPcyv4jN6jYzw11qOOR-xd_w6s5dguQSoHyvmPFSWtL9S+tz3w@mail.gmail.com> (raw)
In-Reply-To: <20150727051258.GB15836@lst.de>
On Sun, Jul 26, 2015 at 10:12 PM, Christoph Hellwig <hch@lst.de> wrote:
> On Sun, Jul 26, 2015 at 10:49:39AM -0700, Dan Williams wrote:
>> On Sun, Jul 26, 2015 at 10:25 AM, Christoph Hellwig <hch@lst.de> wrote:
>> > On Fri, Jul 24, 2015 at 10:38:42PM -0400, Dan Williams wrote:
>> >> The behavior change to return NULL on an unsupported request is reserved
>> >> for a later patch.
>> >
>> > Why?
>>
>> This is for drivers like pmem that care about the mapping type. For
>> example, if pmem can't get a cache-enabled mapping it is potentially
>> putting the write durability of the persistent media at risk.
>
> I understand that part, but the question is why the old behavior
> is retained for now and only changed later.
Oh, because all we have at this point is ioremap_cache() which
silently falls back. It's not until the introduction of
arch_memremp() where we update the arch code to break that behavior.
That said, I think it may be beneficial to allow a fallback if the
user cares. So maybe memremap() can call plain ioremap() if
MEMREMAP_STRICT is not set and none of the other mapping types are
satisfied.
next prev parent reply other threads:[~2015-07-27 23:26 UTC|newest]
Thread overview: 208+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-25 2:37 [PATCH v2 00/25] replace ioremap_{cache|wt} with memremap Dan Williams
2015-07-25 2:37 ` Dan Williams
2015-07-25 2:37 ` Dan Williams
2015-07-25 2:37 ` Dan Williams
2015-07-25 2:37 ` Dan Williams
2015-07-25 2:38 ` [PATCH v2 01/25] mm, x86: Fix warning in ioremap RAM check Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` [PATCH v2 02/25] mm, x86: Remove region_is_ram() call from ioremap Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` [PATCH v2 03/25] mm: Fix bugs in region_is_ram() Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` [PATCH v2 04/25] mm: enhance region_is_ram() to distinguish 'unknown' vs 'mixed' Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-27 22:50 ` Luis R. Rodriguez
2015-07-27 22:50 ` Luis R. Rodriguez
2015-07-27 22:50 ` Luis R. Rodriguez
2015-07-28 21:33 ` Toshi Kani
2015-07-28 21:33 ` Toshi Kani
2015-07-28 21:33 ` Toshi Kani
2015-07-25 2:38 ` [PATCH v2 05/25] arch, drivers: don't include <asm/io.h> directly, use <linux/io.h> instead Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` [PATCH v2 06/25] cleanup IORESOURCE_CACHEABLE vs ioremap() Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` [PATCH v2 07/25] intel_iommu: fix leaked ioremap mapping Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` [PATCH v2 08/25] arch: introduce memremap() Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-26 17:25 ` Christoph Hellwig
2015-07-26 17:25 ` Christoph Hellwig
2015-07-26 17:25 ` Christoph Hellwig
2015-07-26 17:49 ` Dan Williams
2015-07-26 17:49 ` Dan Williams
2015-07-26 17:49 ` Dan Williams
2015-07-27 5:12 ` Christoph Hellwig
2015-07-27 5:12 ` Christoph Hellwig
2015-07-27 5:12 ` Christoph Hellwig
2015-07-27 5:12 ` Christoph Hellwig
2015-07-27 5:12 ` Christoph Hellwig
2015-07-27 5:12 ` Christoph Hellwig
2015-07-27 23:26 ` Dan Williams [this message]
2015-07-27 23:26 ` Dan Williams
2015-07-27 23:26 ` Dan Williams
2015-07-29 6:50 ` Christoph Hellwig
2015-07-29 6:50 ` Christoph Hellwig
2015-07-29 6:50 ` Christoph Hellwig
2015-07-29 18:27 ` Luis R. Rodriguez
2015-07-29 18:27 ` Luis R. Rodriguez
2015-07-29 18:27 ` Luis R. Rodriguez
2015-07-29 18:33 ` Dan Williams
2015-07-29 18:33 ` Dan Williams
2015-07-29 18:33 ` Dan Williams
2015-07-29 21:00 ` Toshi Kani
2015-07-29 21:00 ` Toshi Kani
2015-07-29 21:00 ` Toshi Kani
2015-07-29 21:11 ` Toshi Kani
2015-07-29 21:11 ` Toshi Kani
2015-07-29 21:11 ` Toshi Kani
2015-07-29 21:43 ` Luis R. Rodriguez
2015-07-29 21:43 ` Luis R. Rodriguez
2015-07-29 21:43 ` Luis R. Rodriguez
2015-07-29 21:47 ` Dan Williams
2015-07-29 21:47 ` Dan Williams
2015-07-29 21:47 ` Dan Williams
2015-07-29 21:52 ` Luis R. Rodriguez
2015-07-29 21:52 ` Luis R. Rodriguez
2015-07-29 21:52 ` Luis R. Rodriguez
2015-07-30 0:00 ` Toshi Kani
2015-07-30 0:00 ` Toshi Kani
2015-07-30 0:00 ` Toshi Kani
2015-08-11 21:30 ` Luis R. Rodriguez
2015-08-11 21:30 ` Luis R. Rodriguez
2015-08-11 21:30 ` Luis R. Rodriguez
2015-08-11 22:40 ` Toshi Kani
2015-08-11 22:40 ` Toshi Kani
2015-08-11 22:40 ` Toshi Kani
2015-08-11 22:52 ` Luis R. Rodriguez
2015-08-11 22:52 ` Luis R. Rodriguez
2015-08-11 22:52 ` Luis R. Rodriguez
2015-08-11 23:13 ` Dan Williams
2015-08-11 23:13 ` Dan Williams
2015-08-11 23:13 ` Dan Williams
2016-04-21 12:47 ` Luis R. Rodriguez
2016-04-21 12:47 ` Luis R. Rodriguez
2016-04-21 12:47 ` Luis R. Rodriguez
2016-04-21 12:47 ` Luis R. Rodriguez
2015-07-27 23:17 ` Luis R. Rodriguez
2015-07-27 23:17 ` Luis R. Rodriguez
2015-07-27 23:17 ` Luis R. Rodriguez
2015-07-27 23:31 ` Dan Williams
2015-07-27 23:31 ` Dan Williams
2015-07-27 23:31 ` Dan Williams
2015-07-27 23:31 ` Dan Williams
2015-07-27 23:43 ` Luis R. Rodriguez
2015-07-27 23:43 ` Luis R. Rodriguez
2015-07-27 23:43 ` Luis R. Rodriguez
2015-07-28 0:32 ` Dan Williams
2015-07-28 0:32 ` Dan Williams
2015-07-28 0:32 ` Dan Williams
2015-07-25 2:38 ` [PATCH v2 09/25] arm: switch from ioremap_cache to memremap Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` [PATCH v2 10/25] x86: " Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` [PATCH v2 11/25] gma500: switch from acpi_os_ioremap to ioremap Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:38 ` Dan Williams
2015-07-25 2:39 ` [PATCH v2 12/25] i915: " Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-27 7:50 ` [Intel-gfx] " Daniel Vetter
2015-07-27 7:50 ` Daniel Vetter
2015-07-27 7:50 ` Daniel Vetter
2015-07-27 7:50 ` Daniel Vetter
2015-07-25 2:39 ` [PATCH v2 13/25] acpi: switch from ioremap_cache to memremap Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 23:55 ` Rafael J. Wysocki
2015-07-25 23:55 ` Rafael J. Wysocki
2015-07-25 23:55 ` Rafael J. Wysocki
2015-07-25 2:39 ` [PATCH v2 14/25] toshiba laptop: replace ioremap_cache with ioremap Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:39 ` [PATCH v2 15/25] memconsole: fix __iomem mishandling, switch to memremap Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 22:02 ` Sergei Shtylyov
2015-07-25 22:02 ` Sergei Shtylyov
2015-07-25 22:02 ` Sergei Shtylyov
2015-07-25 2:39 ` [PATCH v2 16/25] visorbus: switch from ioremap_cache " Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:39 ` [PATCH v2 17/25] intel-iommu: " Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-08-03 14:27 ` Joerg Roedel
2015-08-03 14:27 ` Joerg Roedel
2015-08-03 14:27 ` Joerg Roedel
2015-07-25 2:39 ` [PATCH v2 18/25] libnvdimm, pmem: " Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-28 22:51 ` Ross Zwisler
2015-07-28 22:51 ` Ross Zwisler
2015-07-28 22:51 ` Ross Zwisler
2015-07-28 23:06 ` Dan Williams
2015-07-28 23:06 ` Dan Williams
2015-07-28 23:06 ` Dan Williams
2015-07-25 2:39 ` [PATCH v2 19/25] pxa2xx-flash: " Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-10-02 17:51 ` Brian Norris
2015-10-02 17:51 ` Brian Norris
2015-10-02 17:51 ` Brian Norris
2015-10-09 21:33 ` Dan Williams
2015-10-09 21:33 ` Dan Williams
2015-10-09 21:33 ` Dan Williams
2015-07-25 2:39 ` [PATCH v2 20/25] sfi: " Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:39 ` [PATCH v2 21/25] fbdev: switch from ioremap_wt " Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:39 ` Dan Williams
2015-07-25 2:40 ` [PATCH v2 22/25] pmem: " Dan Williams
2015-07-25 2:40 ` Dan Williams
2015-07-25 2:40 ` Dan Williams
2015-07-29 19:12 ` Ross Zwisler
2015-07-29 19:12 ` Ross Zwisler
2015-07-29 19:12 ` Ross Zwisler
2015-07-25 2:40 ` [PATCH v2 23/25] arch: remove ioremap_cache, replace with arch_memremap Dan Williams
2015-07-25 2:40 ` Dan Williams
2015-07-25 2:40 ` Dan Williams
2015-07-26 17:31 ` Christoph Hellwig
2015-07-26 17:31 ` Christoph Hellwig
2015-07-26 17:31 ` Christoph Hellwig
2015-07-25 2:40 ` [PATCH v2 24/25] arch: remove ioremap_wt, " Dan Williams
2015-07-25 2:40 ` Dan Williams
2015-07-25 2:40 ` Dan Williams
2015-07-26 17:31 ` Christoph Hellwig
2015-07-26 17:31 ` Christoph Hellwig
2015-07-26 17:31 ` Christoph Hellwig
2015-07-27 8:03 ` Christoph Hellwig
2015-07-27 8:03 ` Christoph Hellwig
2015-07-27 8:03 ` Christoph Hellwig
2015-07-29 22:21 ` Dan Williams
2015-07-29 22:21 ` Dan Williams
2015-07-29 22:21 ` Dan Williams
2015-07-25 2:40 ` [PATCH v2 25/25] pmem: convert to generic memremap Dan Williams
2015-07-25 2:40 ` Dan Williams
2015-07-25 2:40 ` Dan Williams
2015-07-26 17:33 ` Christoph Hellwig
2015-07-26 17:33 ` Christoph Hellwig
2015-07-26 17:33 ` Christoph Hellwig
2015-07-26 18:11 ` Dan Williams
2015-07-26 18:11 ` Dan Williams
2015-07-26 18:11 ` Dan Williams
2015-07-27 5:14 ` Christoph Hellwig
2015-07-27 5:14 ` Christoph Hellwig
2015-07-27 5:14 ` Christoph Hellwig
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