x86/asm: add iosubmit_cmds512() based on MOVDIR64B CPU instruction

With the introduction of MOVDIR64B instruction, there is now an instruction
that can write 64 bytes of data atomically.

Quoting from Intel SDM:
"There is no atomicity guarantee provided for the 64-byte load operation
from source address, and processor implementations may use multiple
load operations to read the 64-bytes. The 64-byte direct-store issued
by MOVDIR64B guarantees 64-byte write-completion atomicity. This means
that the data arrives at the destination in a single undivided 64-byte
write transaction."

We have identified at least 3 different use cases for this instruction in
the format of func(dst, src, count):
1) Clear poison / Initialize MKTME memory
   @dst is normal memory.
   @src in normal memory. Does not increment. (Copy same line to all
   targets)
   @count (to clear/init multiple lines)
2) Submit command(s) to new devices
   @dst is a special MMIO region for a device. Does not increment.
   @src is normal memory. Increments.
   @count usually is 1, but can be multiple.
3) Copy to iomem in big chunks
   @dst is iomem and increments
   @src in normal memory and increments
   @count is number of chunks to copy

Add support for case #2 to support device that will accept commands via
this instruction. We provide a @count in order to submit a batch of
preprogrammed descriptors in virtually contiguous memory. This
allows the caller to submit multiple descriptors to a device with a single
submission. The special device requires the entire 64bytes descriptor to
be written atomically and will accept MOVDIR64B instruction.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Acked-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/157965022175.73301.10174614665472962675.stgit@djiang5-desk3.ch.intel.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>