On 07/25/2012 04:36 PM, Paolo Bonzini wrote: > Il 25/07/2012 15:26, Boaz Harrosh ha scritto: >> On 07/25/2012 03:49 PM, Paolo Bonzini wrote: >> >>> >>> Except here the destination array has to be given to virtio, which >>> doesn't (yet) understand chaining. I'm using for_each_sg rather than a >>> simple memcpy exactly because I want to flatten the input scatterlist >>> onto consecutive scatterlist entries, which is what virtio expects (and >>> what I'll change when I get to it). >>> >>> for_each_sg guarantees that I get non-chain scatterlists only, so it is >>> okay to value-assign them to sg[]. >> >> So if the virtio does not understand chaining at all then surly it will >> not understand the 2-bit end marker and will get a wrong page pointer >> with the 1st bit set. > > It doesn't understand chaining, but it does use sg_phys(x) so it will > not get a wrong page pointer for the end marker. > >> Fine then your code is now a crash because the terminating bit was just >> copied over, which it was not before. > > I did test the patch with value-assignment. > Still you should use the sg_set_page()!! 1. It is not allowed to directly manipulate sg entries. One should always use the proper accessor. Even if open coding does work and is not a bug it should not be used anyway! 2. Future code that will support chaining will need to do as I say so why change it then, again? Please don't change two things in one patch. The fix is for high-pages please fix only that here. You can blasphemy open-code the sg manipulation in a separate patch. Please Boaz >> Lets separate the two topics from now on. Send me one mail concerning >> the proper above patch, And a different mail for how to support chaining. > > Ok, and I'll change the topic. > > Paolo -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
