From: Alexander Duyck <alexander.h.duyck@intel.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Konrad Rzeszutek Wilk <konrad@kernel.org>,
tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH v2 0/8] Improve performance of VM translation on x86_64
Date: Fri, 12 Oct 2012 08:53:58 -0700 [thread overview]
Message-ID: <50783D16.5020309@intel.com> (raw)
In-Reply-To: <20121012151517.GC16230@one.firstfloor.org>
On 10/12/2012 08:15 AM, Andi Kleen wrote:
>> Could you also add a blurb in the Documentation/< appropriate file
>> for device driver writes> mentioning the usage of __pa_symbol is
>> preferred?
> Device driver writer's shouldn't use any of this anyways, they should always
> use the PCI DMA APIs and never DMA to the stack or to static variables.
>
> -Andi
__pa_symbol is very architecture specific. From what I can tell it only
exists for the x86 and mips architectures. If a device driver is
expected to function on things such as PowerPC you cannot use it.
Everything I have read indicates that for virtual to physical
translation in drivers it is preferred to use virt_to_phys, not __pa or
__pa_symbol.
Thanks,
Alex
prev parent reply other threads:[~2012-10-12 15:53 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-11 20:49 Alexander Duyck
2012-10-11 20:49 ` [PATCH v2 1/8] x86: Improve __phys_addr performance by making use of carry flags and inlining Alexander Duyck
2012-10-11 20:50 ` [PATCH v2 2/8] x86: Make it so that __pa_symbol can only process kernel symbols on x86_64 Alexander Duyck
2012-10-11 20:50 ` [PATCH v2 3/8] x86: Drop 4 unnecessary calls to __pa_symbol Alexander Duyck
2012-10-11 20:50 ` [PATCH v2 4/8] x86: Use __pa_symbol instead of __pa on C visible symbols Alexander Duyck
2012-10-11 20:50 ` [PATCH v2 5/8] x86/ftrace: " Alexander Duyck
2012-10-11 20:50 ` [PATCH v2 6/8] x86/xen: " Alexander Duyck
2012-10-12 15:12 ` Konrad Rzeszutek Wilk
2012-10-11 20:50 ` [PATCH v2 7/8] x86/acpi: " Alexander Duyck
2012-10-11 20:50 ` [PATCH v2 8/8] x86/lguest: " Alexander Duyck
2012-10-11 22:47 ` Rusty Russell
2012-10-11 22:40 ` [PATCH v2 0/8] Improve performance of VM translation on x86_64 Andi Kleen
2012-10-11 22:58 ` H. Peter Anvin
2012-11-01 16:01 ` Alexander Duyck
2012-10-12 14:12 ` Konrad Rzeszutek Wilk
2012-10-12 15:15 ` Andi Kleen
2012-10-12 15:53 ` Alexander Duyck [this message]
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