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author | Dave Jiang <dave.jiang@intel.com> | 2020-01-21 16:43:41 -0700 |
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committer | Vinod Koul <vkoul@kernel.org> | 2020-01-24 11:18:45 +0530 |
commit | 232bb01bb8ad2f88aefbd88b0d3fe3f9a253502b (patch) | |
tree | 5360bcb62e36fe26d158a466fd6c78916cc13af1 /arch/x86/include/asm/io.h | |
parent | 6c0157be02f02c490dbe74af0d469ed1ddc30b1e (diff) | |
download | linux-stable-232bb01bb8ad2f88aefbd88b0d3fe3f9a253502b.tar.gz linux-stable-232bb01bb8ad2f88aefbd88b0d3fe3f9a253502b.tar.bz2 linux-stable-232bb01bb8ad2f88aefbd88b0d3fe3f9a253502b.zip |
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>
Diffstat (limited to 'arch/x86/include/asm/io.h')
-rw-r--r-- | arch/x86/include/asm/io.h | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h index 9997521fc5cd..e1aa17a468a8 100644 --- a/arch/x86/include/asm/io.h +++ b/arch/x86/include/asm/io.h @@ -399,4 +399,40 @@ extern bool arch_memremap_can_ram_remap(resource_size_t offset, extern bool phys_mem_access_encrypted(unsigned long phys_addr, unsigned long size); +/** + * iosubmit_cmds512 - copy data to single MMIO location, in 512-bit units + * @__dst: destination, in MMIO space (must be 512-bit aligned) + * @src: source + * @count: number of 512 bits quantities to submit + * + * Submit data from kernel space to MMIO space, in units of 512 bits at a + * time. Order of access is not guaranteed, nor is a memory barrier + * performed afterwards. + * + * Warning: Do not use this helper unless your driver has checked that the CPU + * instruction is supported on the platform. + */ +static inline void iosubmit_cmds512(void __iomem *__dst, const void *src, + size_t count) +{ + /* + * Note that this isn't an "on-stack copy", just definition of "dst" + * as a pointer to 64-bytes of stuff that is going to be overwritten. + * In the MOVDIR64B case that may be needed as you can use the + * MOVDIR64B instruction to copy arbitrary memory around. This trick + * lets the compiler know how much gets clobbered. + */ + volatile struct { char _[64]; } *dst = __dst; + const u8 *from = src; + const u8 *end = from + count * 64; + + while (from < end) { + /* MOVDIR64B [rdx], rax */ + asm volatile(".byte 0x66, 0x0f, 0x38, 0xf8, 0x02" + : "=m" (dst) + : "d" (from), "a" (dst)); + from += 64; + } +} + #endif /* _ASM_X86_IO_H */ |