Optimize i386 memory barriers
Optimize i386 memory barriers

Use identical memory barrier implementations on 32 and 64 bit Intel CPUs.
In the past the Linux kernel supported 32 bit CPUs that violate the x86
ordering standard. Since io_uring is not supported by these older kernels,
do not support these older CPUs in liburing. See also Linux kernel commit
5927145efd5d ("x86/cpu: Remove the CONFIG_X86_PPRO_FENCE=y quirk") # v4.16.

Cc: Roman Penyaev <5ffa6b82cf9ad80649a6dfab98886ec472da14b5@suse.de>
Suggested-by: Roman Penyaev <5ffa6b82cf9ad80649a6dfab98886ec472da14b5@suse.de>
Signed-off-by: Bart Van Assche <89ed62d80e76c0eb24ee0d6433b48a91c2273b5e@acm.org>
Signed-off-by: Jens Axboe <cd8c6775e60d6f67a6984377324e5290df3d5358@kernel.dk>

axboe/liburing,axboe/liburing,axboe/liburing