On Fri, 2013-09-13 at 22:50 -0500, Scott Wood wrote: > The ISA says that a sync is needed to order a PTE write with a > subsequent hardware tablewalk lookup. On e6500, without this sync > we've been observed to die with a DSI due to a PTE write not being seen > by a subsequent access, even when everything happens on the same > CPU.
This is gross, I didn't realize we had that bogosity in the architecture... Did you measure the performance impact ? Cheers, Ben. > Signed-off-by: Scott Wood <scottw...@freescale.com> > --- > v2: new patch > > Note that we saw this problem when running in emulation (died early in > boot), but when I tried just now with the mb() removed on actual > hardware, I didn't see any problem. But since I'm not aware of any > change having been made in the hardware relative to this, and since it > is architecturally required, I'd be more comfortable leaving it in > unlesss something has changed in the kernel recently such that a sync > is happening somewhere else along the code path. > --- > arch/powerpc/include/asm/pgtable.h | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/arch/powerpc/include/asm/pgtable.h > b/arch/powerpc/include/asm/pgtable.h > index 7d6eacf..0459077 100644 > --- a/arch/powerpc/include/asm/pgtable.h > +++ b/arch/powerpc/include/asm/pgtable.h > @@ -143,6 +143,13 @@ static inline void __set_pte_at(struct mm_struct *mm, > unsigned long addr, > * cases, and 32-bit non-hash with 32-bit PTEs. > */ > *ptep = pte; > +#ifdef CONFIG_PPC_BOOK3E_64 > + /* > + * With hardware tablewalk, a sync is needed to ensure that > + * subsequent accesses see the PTE we just wrote. > + */ > + mb(); > +#endif > #endif > } > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
