linux-kernel - Re: [PATCH] X86: MM: Add PAT Type write-through in combination with mtrr

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: <20131028101749.GA4389@gmail.com>
Date:	Mon, 28 Oct 2013 11:17:49 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Andreas Werner <wernerandy@....de>
Cc:	Borislav Petkov <bp@...en8.de>, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, x86@...nel.org,
	dave@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] X86: MM: Add PAT Type write-through in combination with
 mtrr


* Andreas Werner <wernerandy@....de> wrote:

> > IOW, you probably could use a WC buffer here too, as it would 
> > combine the writes coming from the FPGA.
> > 
> > Btw, there's also mtrr_add(..., MTRR_TYPE_WRTHROUGH, ) if you 
> > must use a WT thing. Have you tried that?
> 
> For reading i need to map the mmio with attributes that allow 
> cache-line read. Therefore i use WT. For the Virtual address i use 
> ioremap_cache in combination with this patch to get an effective 
> memory type of "Write-Through". This allows me to read from the 
> mmio with "PCIe burst". The write behaviour to this region do not 
> matter.

And regular write-back cacheable isn't sufficient because the CPU 
could do things like prefetch your range automatically?

If the reads are for packet data and not for commands, WB could 
still be beneficial as it should allow even higher bandwidth. (For 
non-data with real semantics WB is probably not good.)

Thanks,

	Ingo
--
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/