On Sat, Feb 16, 2019 at 08:22:12AM -0600, Segher Boessenkool wrote: > Hi all, > > On Sat, Feb 16, 2019 at 09:55:11PM +1100, Balbir Singh wrote: > > On Thu, Feb 14, 2019 at 05:23:39PM +1100, Michael Ellerman wrote: > > > In v4.20 we changed our pgd/pud_present() to check for _PAGE_PRESENT > > > rather than just checking that the value is non-zero, e.g.: > > > > > > static inline int pgd_present(pgd_t pgd) > > > { > > > - return !pgd_none(pgd); > > > + return (pgd_raw(pgd) & cpu_to_be64(_PAGE_PRESENT)); > > > } > > > > > > Unfortunately this is broken on big endian, as the result of the > > > bitwise && is truncated to int, which is always zero because > > (Bitwise "&" of course). > > > Not sure why that should happen, why is the result an int? What > > causes the casting of pgd_t & be64 to be truncated to an int. > > Yes, it's not obvious as written... It's simply that the return type of > pgd_present is int. So it is truncated _after_ the bitwise and. >
Thanks, I am surprised the compiler does not complain about the truncation of bits. I wonder if we are missing -Wconversion Balbir