linux-kernel - Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops

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Message-ID: <20071211143224.15900995@tux.DEF.witbe.net>
Date:	Tue, 11 Dec 2007 14:32:24 +0100
From:	Paul Rolland <rol@...917.net>
To:	Rene Herman <rene.herman@...access.nl>
Cc:	David Newall <david@...idnewall.com>,
	"H. Peter Anvin" <hpa@...or.com>, Krzysztof Halasa <khc@...waw.pl>,
	Pavel Machek <pavel@....cz>, Andi Kleen <andi@...stfloor.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	"David P. Reed" <dpreed@...d.com>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, rol@...be.net
Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64
 with MCP51 laptops

Hello,

On Tue, 11 Dec 2007 14:16:01 +0100
Rene Herman <rene.herman@...access.nl> wrote:

> On 11-12-07 13:08, David Newall wrote:
> 
> > Rene Herman wrote:

> (*) some local testing shows it to be almost exactly that for both out and 
> in on my own PC -- a little over. If anyone cares, see attached little test 
> program. The "little over" I don't worry about. 0 us delay is also fine for 
> me and if any code was _that_ fragile it would have broken long ago.

Some results :

Core 2Duo 1.73GHz :
[root@tux tmp]# ./in
out = 2366
in  = 2496
[root@tux tmp]# ./in
out = 3094
in  = 2379

Plain old PIII 600 MHz:
[root@...-dev /tmp]# ./in 
out = 314
in  = 543
[root@...-dev /tmp]# ./in 
out = 319
in  = 538
[root@...-dev /tmp]# ./in 
out = 319
in  = 550
[root@...-dev /tmp]# ./in 
out = 329
in  = 531

Opteron 150 2.4GHz :
-bash-3.1# ./in
out = 4801
in  = 4863
-bash-3.1# ./in
out = 5041
in  = 4909
-bash-3.1# ./in
out = 4829
in  = 4886

Paul

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