linux-kernel - Re: [PATCH v10 12/12] drivers/block/pmem: Map NVDIMM with ioremap

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Date:	Fri, 29 May 2015 11:11:30 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Toshi Kani <toshi.kani@...com>,
	Dan Williams <dan.j.williams@...el.com>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc:	hpa@...or.com, tglx@...utronix.de, mingo@...hat.com,
	akpm@...ux-foundation.org, arnd@...db.de, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	linux-nvdimm@...ts.01.org, jgross@...e.com,
	stefan.bader@...onical.com, luto@...capital.net, hmh@....eng.br,
	yigal@...xistor.com, konrad.wilk@...cle.com, Elliott@...com,
	mcgrof@...e.com, hch@....de
Subject: Re: [PATCH v10 12/12] drivers/block/pmem: Map NVDIMM with
 ioremap_wt()

On Wed, May 27, 2015 at 09:19:04AM -0600, Toshi Kani wrote:
> 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>
> ---
>  drivers/block/pmem.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/block/pmem.c b/drivers/block/pmem.c
> index eabf4a8..095dfaa 100644
> --- a/drivers/block/pmem.c
> +++ b/drivers/block/pmem.c
> @@ -139,11 +139,11 @@ static struct pmem_device *pmem_alloc(struct device *dev, struct resource *res)
>  	}
>  
>  	/*
> -	 * Map the memory as non-cachable, as we can't write back the contents
> +	 * Map the memory as write-through, as we can't write back the contents
>  	 * of the CPU caches in case of a crash.
>  	 */
>  	err = -ENOMEM;
> -	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?

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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