Re: [PATCH 12/33] tools headers: Import iosubmit_cmds512()

[Vinicius Costa Gomes <vinicius.gomes@intel.com>]

David Matlack <dmatlack@google.com> writes:

> Import iosubmit_cmds512() from arch/x86/include/asm/io.h into tools/ so
> it can be used by VFIO selftests to interact with Intel DSA devices.
>

minor: perhaps move this patch to be near the one that adds the DSA
driver? (in case there's a next revision)

Anyway,

Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>

> Also pull in movdir64b() from arch/x86/include/asm/special_insns.h into
> tools/, which is the underlying instruction used by iosubmit_cmds512().
>
> Changes made when importing: None
>
> Signed-off-by: David Matlack <dmatlack@google.com>
> ---
>  tools/arch/x86/include/asm/io.h            | 26 +++++++++++++++++++++
>  tools/arch/x86/include/asm/special_insns.h | 27 ++++++++++++++++++++++
>  2 files changed, 53 insertions(+)
>  create mode 100644 tools/arch/x86/include/asm/special_insns.h
>
> diff --git a/tools/arch/x86/include/asm/io.h b/tools/arch/x86/include/asm/io.h
> index 4c787a2363de..ecad61a3ea52 100644
> --- a/tools/arch/x86/include/asm/io.h
> +++ b/tools/arch/x86/include/asm/io.h
> @@ -4,6 +4,7 @@
>  
>  #include <linux/compiler.h>
>  #include <linux/types.h>
> +#include "special_insns.h"
>  
>  #define build_mmio_read(name, size, type, reg, barrier) \
>  static inline type name(const volatile void __iomem *addr) \
> @@ -72,4 +73,29 @@ build_mmio_write(__writeq, "q", u64, "r", )
>  
>  #include <asm-generic/io.h>
>  
> +/**
> + * 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)
> +{
> +	const u8 *from = src;
> +	const u8 *end = from + count * 64;
> +
> +	while (from < end) {
> +		movdir64b(dst, from);
> +		from += 64;
> +	}
> +}
> +
>  #endif /* _TOOLS_ASM_X86_IO_H */
> diff --git a/tools/arch/x86/include/asm/special_insns.h b/tools/arch/x86/include/asm/special_insns.h
> new file mode 100644
> index 000000000000..04af42a99c38
> --- /dev/null
> +++ b/tools/arch/x86/include/asm/special_insns.h
> @@ -0,0 +1,27 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _TOOLS_ASM_X86_SPECIAL_INSNS_H
> +#define _TOOLS_ASM_X86_SPECIAL_INSNS_H
> +
> +/* The dst parameter must be 64-bytes aligned */
> +static inline void movdir64b(void *dst, const void *src)
> +{
> +	const struct { char _[64]; } *__src = src;
> +	struct { char _[64]; } *__dst = dst;
> +
> +	/*
> +	 * MOVDIR64B %(rdx), rax.
> +	 *
> +	 * Both __src and __dst must be memory constraints in order to tell the
> +	 * compiler that no other memory accesses should be reordered around
> +	 * this one.
> +	 *
> +	 * Also, both must be supplied as lvalues because this tells
> +	 * the compiler what the object is (its size) the instruction accesses.
> +	 * I.e., not the pointers but what they point to, thus the deref'ing '*'.
> +	 */
> +	asm volatile(".byte 0x66, 0x0f, 0x38, 0xf8, 0x02"
> +		     : "+m" (*__dst)
> +		     :  "m" (*__src), "a" (__dst), "d" (__src));
> +}
> +
> +#endif /* _TOOLS_ASM_X86_SPECIAL_INSNS_H */
> -- 
> 2.50.0.rc2.701.gf1e915cc24-goog
>

-- 
Vinicius