[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] xen: fix alignment for bitops
On 15/04/14 14:13, Vladimir Murzin wrote: > On Tue, Apr 15, 2014 at 2:05 PM, Vladimir Murzin <murzin.v@xxxxxxxxx> wrote: >> On Tue, Apr 15, 2014 at 11:17 AM, David Vrabel <david.vrabel@xxxxxxxxxx> >> wrote: >>> On 14/04/14 21:43, Vladimir Murzin wrote: >>>> Bitops operations like set/clear/change mandate world aligned pointer, >>>> mainly >>>> because architectures specific implementation. >>>> >>>> Looks that DEFINE_PER_CPU does required alignment for cpu_control_block; >>>> however, local copy used for bitops might not be world aligned. >>>> >>>> Instruct compiler to keep local copy of "ready" world aligned. >>> [...] >>>> --- a/drivers/xen/events/events_fifo.c >>>> +++ b/drivers/xen/events/events_fifo.c >>>> @@ -285,7 +285,7 @@ static void consume_one_event(unsigned cpu, >>>> static void evtchn_fifo_handle_events(unsigned cpu) >>>> { >>>> struct evtchn_fifo_control_block *control_block; >>>> - uint32_t ready; >>>> + uint32_t __aligned(sizeof(long)) ready; >>> >>> This doesn't look sufficient to me. The event words within the event >>> array are 32-bit sized/aligned and sync_set_bit() and sync_clear_bit() >>> etc. are done on these words. >>> >>> I think arm64 is going to have to provide sync_clear_bit(), >>> sync_set_bit(), sync_test_bit() and sync_test_and_set_bit() that work >>> with 32-bit sized and aligned words. >> >> Looks reasonable. If I understand correctly these sync_* functions are >> used by Xen only (or at least was introduced because of Xen). >> I might take rework them for arm64 to operate on 32-bit >> size/alignment. Does this sounds reasonable? >> ... and what to do with this patch? >> > > I think it could be dropped if clear_bit(priority, BM(ready)) is > replaced with sync_ equivalent. ready can be unsigned long as Ian suggested. David _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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