linux-kernel - Re: [PATCH][RFC] asm-generic:remove calling flush_write_buffers() in dma_sync_*_for

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <d82e647a0906290754t13bc1b37s6ea6fd582a7fdbe@mail.gmail.com>
Date:	Mon, 29 Jun 2009 22:54:51 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Joerg Roedel <joerg.roedel@....com>
Cc:	Arnd Bergmann <arnd@...db.de>, fujita.tomonori@....ntt.co.jp,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: [PATCH][RFC] asm-generic:remove calling flush_write_buffers() in 
	dma_sync_*_for_cpu

2009/6/29 Joerg Roedel <joerg.roedel@....com>:
>>
>> IMHO, even we do not call flush_write_buffer(), CPU can read correct
>> data from the
>> dma buffer since write buffer can't affect cache, right?
>
> flush_write_buffer is not about cache flushing. It is about read/write
> reordering in the CPU. Think of it as a memory barrier. On most x86

You mean we may need a memory barrier between writing data from bouncing buffer
to dma buffer and reading data from dma buffer, do you?

> systems this function is therefore a nop. Cache flushing for
> architectures without cache-coherent DMA is typically handled in their
> low-level dma-api code (I have seen that at least in parisc32).



-- 
Lei Ming
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/