On Thu, Sep 17, 2020 at 02:15:23PM -0700, Dave Jiang wrote: > Add enqcmds() in x86 io.h instead of special_insns.h.
Why? It is an asm wrapper for a special instruction. > MOVDIR64B > instruction can be used for other purposes. A wrapper was introduced > in io.h for its command submission usage. ENQCMDS has a single > purpose of submit 64-byte commands to supported devices and should > be called directly. > > Signed-off-by: Dave Jiang <[email protected]> > Reviewed-by: Tony Luck <[email protected]> > --- > arch/x86/include/asm/io.h | 29 +++++++++++++++++++++++++++++ > 1 file changed, 29 insertions(+) > > diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h > index d726459d08e5..b7af0bf8a018 100644 > --- a/arch/x86/include/asm/io.h > +++ b/arch/x86/include/asm/io.h > @@ -424,4 +424,33 @@ static inline void iosubmit_cmds512(void __iomem *dst, > const void *src, > } > } > > +/** > + * enqcmds - copy a 512 bits data unit to single MMIO location Your #319433 doc says "ENQCMDS — Enqueue Command Supervisor" Now *how* that enqueueing is done you can explain in the comment below. > + * @dst: destination, in MMIO space (must be 512-bit aligned) > + * @src: source > + * > + * Submit data from kernel space to MMIO space, in a unit of 512 bits. > + * Order of data access is not guaranteed, nor is a memory barrier > + * performed afterwards. The command returns false (0) on failure, and true > (1) > + * on success. The command or the function? >From what I see below, the instruction sets ZF=1 to denote that it needs to be retried and ZF=0 means success, as the doc says. And in good UNIX tradition, 0 means usually success and !0 failure. So why are you flipping that? > + * Warning: Do not use this helper unless your driver has checked that the > CPU > + * instruction is supported on the platform. > + */ > +static inline bool enqcmds(void __iomem *dst, const void *src) > +{ > + bool retry; > + > + /* ENQCMDS [rdx], rax */ > + asm volatile(".byte 0xf3, 0x0f, 0x38, 0xf8, 0x02, 0x66, 0x90\t\n" ^^^^ No need for those last two chars. > + CC_SET(z) > + : CC_OUT(z) (retry) > + : "a" (dst), "d" (src)); <---- newline here. > + /* Submission failure is indicated via EFLAGS.ZF=1 */ > + if (retry) > + return false; > + > + return true; > +} > + > #endif /* _ASM_X86_IO_H */ Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette
