Date: Wed, 18 Feb 2015 21:44:14 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Toshi Kani <toshi.kani@hp.com>
Cc: akpm@linux-foundation.org, hpa@zytor.com, tglx@linutronix.de,
        mingo@redhat.com, arnd@arndb.de, linux-mm@kvack.org, x86@kernel.org,
        linux-kernel@vger.kernel.org, Elliott@hp.com
Subject: Re: [PATCH v2 6/7] x86, mm: Support huge I/O mappings on x86
Message-ID: <20150218204414.GA20943@gmail.com>
References: <1423521935-17454-1-git-send-email-toshi.kani@hp.com>
 <1423521935-17454-7-git-send-email-toshi.kani@hp.com>
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* Toshi Kani <toshi.kani@hp.com> wrote:

> This patch implements huge I/O mapping capability interfaces on x86.

> +#ifdef CONFIG_HUGE_IOMAP
> +#ifdef CONFIG_X86_64
> +#define IOREMAP_MAX_ORDER       (PUD_SHIFT)
> +#else
> +#define IOREMAP_MAX_ORDER       (PMD_SHIFT)
> +#endif
> +#endif  /* CONFIG_HUGE_IOMAP */

> +#ifdef CONFIG_HUGE_IOMAP

Hm, so why is there a Kconfig option for this? It just 
complicates things.

For example the kernel already defaults to mapping itself 
with as large mappings as possible, without a Kconfig entry 
for it. There's no reason to make this configurable - and 
quite a bit of complexity in the patches comes from this 
configurability.

Thanks,

	Ingo
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