On Thu, Sep 06, 2007 at 05:40:38AM -0700, David Miller wrote:
> From: Matthew Wilcox <[email protected]>
> 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?
thanks,
greg k-h
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