On Thu, Dec 01, 2016 at 02:36:05PM +0300, Andrey Ryabinin wrote: > On 11/29/2016 09:55 PM, Laura Abbott wrote: > > __pa_symbol is the correct API to find the physical address of symbols. > > Switch to it to allow for debugging APIs to work correctly. > > But __pa() is correct for symbols. I see how __pa_symbol() might be a little > faster than __pa(), but there is nothing wrong in using __pa() on symbols. While it's true today that __pa() works on symbols, this is for pragmatic reasons (allowing existing code to work until it is all cleaned up), and __pa_symbol() is the correct API to use. Relying on this means that __pa() can't be optimised for the (vastly common) case of translating linear map addresses. Consistent use of __pa_symbol() will allow for subsequent optimisation of __pa() in the common case, in adition to being necessary for arm64's DEBUG_VIRTUAL. > > Other functions such as p*d_populate may call __pa internally. > > Ensure that the address passed is in the linear region by calling > > lm_alias. > > Why it should be linear mapping address? __pa() translates kernel > image address just fine. As above, while that's true today, but is something that we wish to change. > Generated code is probably worse too. Even if that is the case, given this is code run once at boot on a debug build, I think it's outweighed by the gain from DEBUG_VIRTUAL, and as a step towards optimising __pa(). Thanks, Mark. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>