Re: [resend] powerpc/64s: fix page table fragment refcount race vs speculative references

2018-08-08 Thread Michael Ellerman
On Fri, 2018-07-27 at 11:48:17 UTC, Nicholas Piggin wrote: > The page table fragment allocator uses the main page refcount racily > with respect to speculative references. A customer observed a BUG due > to page table page refcount underflow in the fragment allocator. This > can be caused by the fr

Re: [PATCH resend] powerpc/64s: fix page table fragment refcount race vs speculative references

2018-07-31 Thread Nicholas Piggin
On Tue, 31 Jul 2018 21:42:22 +1000 Michael Ellerman wrote: > Nicholas Piggin writes: > > On Fri, 27 Jul 2018 08:38:35 -0700 > > Matthew Wilcox wrote: > >> On Sat, Jul 28, 2018 at 12:29:06AM +1000, Nicholas Piggin wrote: > >> > On Fri, 27 Jul 2018 06:41:56 -0700 > >> > Matthew Wilcox wrote:

Re: [PATCH resend] powerpc/64s: fix page table fragment refcount race vs speculative references

2018-07-31 Thread Michael Ellerman
Nicholas Piggin writes: > On Fri, 27 Jul 2018 08:38:35 -0700 > Matthew Wilcox wrote: >> On Sat, Jul 28, 2018 at 12:29:06AM +1000, Nicholas Piggin wrote: >> > On Fri, 27 Jul 2018 06:41:56 -0700 >> > Matthew Wilcox wrote: >> > > On Fri, Jul 27, 2018 at 09:48:17PM +1000, Nicholas Piggin wrote: >>

Re: [PATCH resend] powerpc/64s: fix page table fragment refcount race vs speculative references

2018-07-27 Thread Nicholas Piggin
On Fri, 27 Jul 2018 08:38:35 -0700 Matthew Wilcox wrote: > On Sat, Jul 28, 2018 at 12:29:06AM +1000, Nicholas Piggin wrote: > > On Fri, 27 Jul 2018 06:41:56 -0700 > > Matthew Wilcox wrote: > > > > > On Fri, Jul 27, 2018 at 09:48:17PM +1000, Nicholas Piggin wrote: > > > > The page table frag

Re: [PATCH resend] powerpc/64s: fix page table fragment refcount race vs speculative references

2018-07-27 Thread Matthew Wilcox
On Sat, Jul 28, 2018 at 12:29:06AM +1000, Nicholas Piggin wrote: > On Fri, 27 Jul 2018 06:41:56 -0700 > Matthew Wilcox wrote: > > > On Fri, Jul 27, 2018 at 09:48:17PM +1000, Nicholas Piggin wrote: > > > The page table fragment allocator uses the main page refcount racily > > > with respect to spe

Re: [PATCH resend] powerpc/64s: fix page table fragment refcount race vs speculative references

2018-07-27 Thread Nicholas Piggin
On Fri, 27 Jul 2018 06:41:56 -0700 Matthew Wilcox wrote: > On Fri, Jul 27, 2018 at 09:48:17PM +1000, Nicholas Piggin wrote: > > The page table fragment allocator uses the main page refcount racily > > with respect to speculative references. A customer observed a BUG due > > to page table page ref

Re: [PATCH resend] powerpc/64s: fix page table fragment refcount race vs speculative references

2018-07-27 Thread Matthew Wilcox
On Fri, Jul 27, 2018 at 09:48:17PM +1000, Nicholas Piggin wrote: > The page table fragment allocator uses the main page refcount racily > with respect to speculative references. A customer observed a BUG due > to page table page refcount underflow in the fragment allocator. This > can be caused by

[PATCH resend] powerpc/64s: fix page table fragment refcount race vs speculative references

2018-07-27 Thread Nicholas Piggin
The page table fragment allocator uses the main page refcount racily with respect to speculative references. A customer observed a BUG due to page table page refcount underflow in the fragment allocator. This can be caused by the fragment allocator set_page_count stomping on a speculative reference