fxsave and xsave require the target address to be 16-/64-byte aligned.
kmalloc(_node) does not (yet) offer such fine-grained control over
alignment[0,1], even though it does "the right thing" most of the time
for power-of-2 sizes. unfortunately, alignment is completely off when
using certain debugging or hardening features/configs, such as KASAN,
slub_debug=Z or the not-yet-upstream SLAB_CANARY.
Use alloc_pages_node() instead which allows us to allocate page-aligned
memory. Since fpregs_state is padded to a full page anyway, and this
code is only relevant for x86 which has 4k pages, this approach should
not allocate any unnecessary memory but still guarantee the needed
alignment.
0: https://lwn.net/Articles/787740/
1: https://lore.kernel.org/linux-block/20190826111627.7505-1-vbabka@suse.cz/
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#9608Closes#9674
b119e2c6f1