Messages in this thread | | | Subject | Re: [RFC] disable PCIE 'Enable No Snoop' bit by default | From | Shaohua Li <> | Date | Tue, 11 Sep 2007 09:29:43 +0800 |
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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. - 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/
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