[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2 24/30] tools/libxc: Modify bitmap operations to take void pointers
On Wed, Feb 10, 2016 at 10:07:12AM +0000, Andrew Cooper wrote: > On 08/02/16 16:36, Ian Campbell wrote: > > On Mon, 2016-02-08 at 16:23 +0000, Tim Deegan wrote: > >> At 13:42 +0000 on 05 Feb (1454679737), Andrew Cooper wrote: > >>> The type of the pointer to a bitmap is not interesting; it does not > >>> affect the > >>> representation of the block of bits being pointed to. > >> It does affect the alignment, though. Is this safe on ARM? > > Good point. These constructs in the patch: > > > > + const unsigned long *addr = _addr; > > > > Would be broken if _addr were not suitably aligned for an unsigned long. > > > > That probably rules out this approach unfortunately. > > What about reworking libxc bitops in terms of unsigned char? That > should cover all alignment issues. See 3cab67ac83b1d56c3daedd9c4adfed497a114246 "+/* + * xc_bitops.h has macros that do this as well - however they assume that + * the bitmask is word aligned but xc_cpumap_t is only guaranteed to be + * byte aligned and so we need byte versions for architectures which do + * not support misaligned accesses (which is basically everyone + * but x86, although even on x86 it can be inefficient). + */ " > > ~Andrew > > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxx > http://lists.xen.org/xen-devel _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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