On Tue, 1 Aug 2017 13:39:06 -0400 [email protected] wrote: > Kernel panic when calling the IRQ-safe __get_user_pages_fast in NMI > handler. > > The bug was introduced by commit: > > 2947ba054a4d ("x86/mm/gup: Switch GUP to the generic > get_user_page_fast() implementation") > > The original x86 __get_user_page_fast used plain get_page() or > page_ref_add(). However, the generic __get_user_page_fast uses > page_cache_get_speculative(), which has VM_BUG_ON(in_interrupt()). > > There is no reason to prevent page_cache_get_speculative from using in > interrupt context. According to the author, putting a BUG_ON there is > just because the code is not verifying correctness of interrupt races. > I did some tests in interrupt context. There is no issue found. > Removing VM_BUG_ON(in_interrupt()) for page_cache_get_speculative().
What code calls page_cache_get_speculative() from NMI context? I'm trying to work out which kernel versions need this fix, but there isn't enough info in the changelog for this. Please don't do that.
