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From: Ingo Molnar <mingo@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Toshi Kani <toshi.kani@hp.com>,
	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 0/7] Kernel huge I/O mapping support
Date: Tue, 24 Feb 2015 09:09:27 +0100	[thread overview]
Message-ID: <20150224080927.GB19069@gmail.com> (raw)
In-Reply-To: <20150223122224.c55554325cc4dadeca067234@linux-foundation.org>


* Andrew Morton <akpm@linux-foundation.org> wrote:

> <reads the code>
> 
> Oh.  We don't do any checking at all.  We're just telling 
> userspace programmers "don't do that".  hrm.  What are 
> your thoughts on adding the overlap checks to the kernel?

I have requested such sanity checking in previous review as 
well, it has to be made fool-proof for this optimization to 
be usable.

Another alternative would be to make this not a transparent 
optimization, but a separate API: ioremap_hugepage() or so.

The devices and drivers dealing with GBs of remapped pages 
is still relatively low, so they could make explicit use of 
the API and opt in to it.

What I was arguing against was to make it a CONFIG_ option: 
that achieves very little in practice, such APIs should be 
uniformly available.

Thanks,

	Ingo

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WARNING: multiple messages have this Message-ID (diff)
From: Ingo Molnar <mingo@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Toshi Kani <toshi.kani@hp.com>,
	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 0/7] Kernel huge I/O mapping support
Date: Tue, 24 Feb 2015 09:09:27 +0100	[thread overview]
Message-ID: <20150224080927.GB19069@gmail.com> (raw)
In-Reply-To: <20150223122224.c55554325cc4dadeca067234@linux-foundation.org>


* Andrew Morton <akpm@linux-foundation.org> wrote:

> <reads the code>
> 
> Oh.  We don't do any checking at all.  We're just telling 
> userspace programmers "don't do that".  hrm.  What are 
> your thoughts on adding the overlap checks to the kernel?

I have requested such sanity checking in previous review as 
well, it has to be made fool-proof for this optimization to 
be usable.

Another alternative would be to make this not a transparent 
optimization, but a separate API: ioremap_hugepage() or so.

The devices and drivers dealing with GBs of remapped pages 
is still relatively low, so they could make explicit use of 
the API and opt in to it.

What I was arguing against was to make it a CONFIG_ option: 
that achieves very little in practice, such APIs should be 
uniformly available.

Thanks,

	Ingo

  parent reply	other threads:[~2015-02-24  8:09 UTC|newest]

Thread overview: 50+ 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 ` 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   ` 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   ` 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   ` 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   ` Toshi Kani
2015-02-09 22:45 ` [PATCH v2 5/7] x86, mm: Support huge KVA mappings on x86 Toshi Kani
2015-02-09 22:45   ` Toshi Kani
2015-02-10 18:59   ` Dave Hansen
2015-02-10 18:59     ` Dave Hansen
2015-02-10 20:42     ` Toshi Kani
2015-02-10 20:42       ` Toshi Kani
2015-02-10 20:51       ` Dave Hansen
2015-02-10 20:51         ` Dave Hansen
2015-02-10 22:13         ` Toshi Kani
2015-02-10 22:13           ` Toshi Kani
2015-02-10 22:20           ` Toshi Kani
2015-02-10 22:20             ` Toshi Kani
2015-02-10 23:10           ` Toshi Kani
2015-02-10 23:10             ` Toshi Kani
2015-03-03  0:37             ` 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
2015-02-09 22:45   ` Toshi Kani
2015-02-18 20:44   ` Ingo Molnar
2015-02-18 20:44     ` Ingo Molnar
2015-02-18 21:13     ` Toshi Kani
2015-02-18 21:13       ` Toshi Kani
2015-02-18 21:15       ` Ingo Molnar
2015-02-18 21:15         ` Ingo Molnar
2015-02-18 21:33         ` Toshi Kani
2015-02-18 21:33           ` Toshi Kani
2015-02-18 21:57           ` Ingo Molnar
2015-02-18 21:57             ` Ingo Molnar
2015-02-18 22:14             ` Toshi Kani
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
2015-02-09 22:45   ` Toshi Kani
2015-02-23 20:22 ` [PATCH v2 0/7] Kernel huge I/O mapping support Andrew Morton
2015-02-23 20:22   ` Andrew Morton
2015-02-23 23:54   ` Toshi Kani
2015-02-23 23:54     ` Toshi Kani
2015-02-24  8:09   ` Ingo Molnar [this message]
2015-02-24  8:09     ` Ingo Molnar
2015-03-02 15:51     ` Toshi Kani
2015-03-02 15:51       ` Toshi Kani

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