lkml.org 
[lkml]   [2007]   [Sep]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [RFC] disable PCIE 'Enable No Snoop' bit by default
From
Date
On Mon, 2007-09-10 at 23:15 -0700, Greg KH wrote:
> On Tue, Sep 11, 2007 at 09:29:43AM +0800, Shaohua Li wrote:
> > On Sun, 2007-09-09 at 09:43 -0700, Greg KH wrote:
> > > On Thu, Sep 06, 2007 at 05:40:38AM -0700, David Miller wrote:
> > > > From: Matthew Wilcox <matthew@wil.cx>
> > > > Date: Thu, 6 Sep 2007 05:57:31 -0600
> > > >
> > > > > I'm not sure your analysis is correct. Here's what my draft copy of
> > > > > the pcie 2.0 spec says:
> > > > >
> > > > > Enble No Snoop ? If this bit is Set, the Function is permitted to
> > > > > Set the No Snoop bit in the Requester Attributes of transactions it
> > > > > initiates that do not require hardware enforced cache coherency (see
> > > > > Section 2.2.6.5). Note that setting this bit to 1b should not cause
> > > > > a Function to Set the No Snoop attribute on all transactions that it
> > > > > initiates. Even when this bit is Set, a Function is only permitted
> > > > > to Set the No Snoop attribute on a transaction when it can guarantee
> > > > > that the address of the transaction is not stored in any cache in
> > > > > the system. This bit permitted to be hardwired to 0b if a Function
> > > > > would never Set the No Snoop attribute in transactions it initiates.
> > > > > Default value of this bit is 1b.
> > > > >
> > > > > That implies that devices are only allowed to set it when it's safe to
> > > > > do so ... and we don't need to turn it off.
> > > >
> > > > This is my understanding of this area of PCI-E as well, and I
> > > > also agree that therefore we should not turn this bit off.
> > >
> > > I agree. But Shaohua, do you see any problems that this patch fixes?
> > No, I didn't see any breakage, just worry about it's a potential issue.
>
> Hm, well, if you don't mind, I'd like to leave it as is for now, as no
> one is reporting any problems with this, and there seems to be some
> disagreement as to if it is really needed or not.
>
> Is that ok?
Ok.

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

\
 
 \ /
  Last update: 2007-09-11 08:45    [W:0.086 / U:0.192 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site