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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
Date: Wed, 18 Feb 2015 22:15:55 +0100	[thread overview]
Message-ID: <20150218211555.GA22696@gmail.com> (raw)
In-Reply-To: <1424294020.17007.21.camel@misato.fc.hp.com>


* Toshi Kani <toshi.kani@hp.com> wrote:

> On Wed, 2015-02-18 at 21:44 +0100, Ingo Molnar wrote:
> > * 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.
> 
> This Kconfig option was added to disable this feature in 
> case there is an issue. [...]

If bugs are found then they should be fixed.

> [...]  That said, since the patchset also added a new 
> nohugeiomap boot option for the same purpose, I agree 
> that this Kconfig option can be removed.  So, I will 
> remove it in the next version.
> 
> An example of such case is with multiple MTRRs described 
> in patch 0/7.

So the multi-MTRR case should probably be detected and 
handled safely?

Thanks,

	Ingo

  reply	other threads:[~2015-02-18 21:16 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-09 22:45 [PATCH v2 0/7] Kernel huge I/O mapping support Toshi Kani
2015-02-09 22:45 ` [PATCH v2 1/7] mm: Change __get_vm_area_node() to use fls_long() Toshi Kani
2015-02-09 22:45 ` [PATCH v2 2/7] lib: Add huge I/O map capability interfaces Toshi Kani
2015-02-09 22:45 ` [PATCH v2 3/7] mm: Change ioremap to set up huge I/O mappings Toshi Kani
2015-02-09 22:45 ` [PATCH v2 4/7] mm: Change vunmap to tear down huge KVA mappings Toshi Kani
2015-02-09 22:45 ` [PATCH v2 5/7] x86, mm: Support huge KVA mappings on x86 Toshi Kani
2015-02-10 18:59   ` Dave Hansen
2015-02-10 20:42     ` Toshi Kani
2015-02-10 20:51       ` Dave Hansen
2015-02-10 22:13         ` Toshi Kani
2015-02-10 22:20           ` Toshi Kani
2015-02-10 23:10           ` Toshi Kani
2015-03-03  0:37             ` Toshi Kani
2015-02-09 22:45 ` [PATCH v2 6/7] x86, mm: Support huge I/O " Toshi Kani
2015-02-18 20:44   ` Ingo Molnar
2015-02-18 21:13     ` Toshi Kani
2015-02-18 21:15       ` Ingo Molnar [this message]
2015-02-18 21:33         ` Toshi Kani
2015-02-18 21:57           ` Ingo Molnar
2015-02-18 22:14             ` Toshi Kani
2015-02-09 22:45 ` [PATCH v2 7/7] mm: Add config HUGE_IOMAP to enable huge I/O mappings Toshi Kani
2015-02-23 20:22 ` [PATCH v2 0/7] Kernel huge I/O mapping support Andrew Morton
2015-02-23 23:54   ` Toshi Kani
2015-02-24  8:09   ` Ingo Molnar
2015-03-02 15:51     ` Toshi Kani

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