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x86/asm: Carve out a generic movdir64b() helper for general usage 

Carve out the MOVDIR64B inline asm primitive into a generic helper so
that it can be used by other functions. Move it to special_insns.h and
have iosubmit_cmds512() call it.

 [ bp: Massage commit message. ]

Suggested-by: Michael Matz <matz@suse.de>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20201005151126.657029-2-dave.jiang@intel.com
This commit is contained in:
Dave Jiang 2020-10-05 08:11:22 -07:00 committed by Borislav Petkov
parent 20f0afd1fb
commit 0888e1030d
2 changed files with 25 additions and 14 deletions
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17
arch/x86/include/asm/io.h
View File

@ -401,7 +401,7 @@ extern bool phys_mem_access_encrypted(unsigned long phys_addr,
/**
* iosubmit_cmds512 - copy data to single MMIO location, in 512-bit units
* @__dst: destination, in MMIO space (must be 512-bit aligned)
* @dst: destination, in MMIO space (must be 512-bit aligned)
* @src: source
* @count: number of 512 bits quantities to submit
*
@ -412,25 +412,14 @@ extern bool phys_mem_access_encrypted(unsigned long phys_addr,
* 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,
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));
movdir64b(dst, from);
from += 64;
}
}

22
arch/x86/include/asm/special_insns.h
View File

@ -234,6 +234,28 @@ static inline void clwb(volatile void *__p)
#define nop() asm volatile ("nop")
/* 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 /* __KERNEL__ */
#endif /* _ASM_X86_SPECIAL_INSNS_H */