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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>
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@ -399,4 +399,40 @@ extern bool arch_memremap_can_ram_remap(resource_size_t offset,
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extern bool phys_mem_access_encrypted(unsigned long phys_addr,
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unsigned long size);
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/**
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* iosubmit_cmds512 - copy data to single MMIO location, in 512-bit units
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* @__dst: destination, in MMIO space (must be 512-bit aligned)
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* @src: source
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* @count: number of 512 bits quantities to submit
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*
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* Submit data from kernel space to MMIO space, in units of 512 bits at a
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* time. Order of access is not guaranteed, nor is a memory barrier
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* performed afterwards.
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*
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* Warning: Do not use this helper unless your driver has checked that the CPU
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* instruction is supported on the platform.
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*/
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static inline void iosubmit_cmds512(void __iomem *__dst, const void *src,
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size_t count)
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{
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/*
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* Note that this isn't an "on-stack copy", just definition of "dst"
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* as a pointer to 64-bytes of stuff that is going to be overwritten.
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* In the MOVDIR64B case that may be needed as you can use the
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* MOVDIR64B instruction to copy arbitrary memory around. This trick
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* lets the compiler know how much gets clobbered.
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*/
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volatile struct { char _[64]; } *dst = __dst;
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const u8 *from = src;
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const u8 *end = from + count * 64;
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while (from < end) {
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/* MOVDIR64B [rdx], rax */
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asm volatile(".byte 0x66, 0x0f, 0x38, 0xf8, 0x02"
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: "=m" (dst)
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: "d" (from), "a" (dst));
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from += 64;
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}
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}
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#endif /* _ASM_X86_IO_H */
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