linux-kernel - Re: [PATCH v11 12/12] drivers/block/pmem: Map NVDIMM with ioremap

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Message-ID: <CAPcyv4jrZG4YD+kav4SSD1CaXwzJphgJRgwUUeHLSUAcxZqqNg@mail.gmail.com>
Date:	Fri, 29 May 2015 18:18:52 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Toshi Kani <toshi.kani@...com>
Cc:	Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>, Juergen Gross <jgross@...e.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	Luis Rodriguez <mcgrof@...e.com>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Stefan Bader <stefan.bader@...onical.com>,
	Andy Lutomirski <luto@...capital.net>, linux-mm@...ck.org,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v11 12/12] drivers/block/pmem: Map NVDIMM with ioremap_wt()

On Fri, May 29, 2015 at 3:59 PM, Toshi Kani <toshi.kani@...com> wrote:
> From: Toshi Kani <toshi.kani@...com>
>
> The pmem driver maps NVDIMM with ioremap_nocache() as we cannot
> write back the contents of the CPU caches in case of a crash.
>
> This patch changes to use ioremap_wt(), which provides uncached
> writes but cached reads, for improving read performance.
>
> Signed-off-by: Toshi Kani <toshi.kani@...com>

Acked-by: Dan Williams <dan.j.williams@...el.com>

...with the caveat that I'm going to follow in behind this series with
generic ioremap_cache() enabling and converting pmem to use
persistent_copy() / persistent_sync() when the arch/cpu has persistent
memory synchronization instructions.  After the conversion
ioremap_wt() will still be there for the non-persistent_sync() capable
case.
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