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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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.