Re: [patch V4 part 5 13/31] x86/irq: Convey vector as argument and not in ptregs

Lai Jiangshan
2020-05-11T15:11:57Z

Hello

On Mon, May 11, 2020 at 10:35 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> Lai,
>
> Lai Jiangshan <jiangshanlai+lkml@gmail.com> writes:
> > On Tue, May 5, 2020 at 10:23 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> >> +SYM_CODE_START(irq_entries_start)
> >> + vector=FIRST_EXTERNAL_VECTOR
> >> + .rept (FIRST_SYSTEM_VECTOR - FIRST_EXTERNAL_VECTOR)
> >> + UNWIND_HINT_IRET_REGS
> >> + .byte 0x6a, vector
> >> + jmp common_interrupt
> >> + .align 8
> >> + vector=vector+1
> >> + .endr
> >> +SYM_CODE_END(irq_entries_start)
> >
> > Using ".byte 0x6a, vector" is somewhat ugly.
> >
> > I hope it should be " pushq $(s8_to_s64(vector))", which can also
> > help to reduce bunches of comments about ".byte 0x6a, vector".
> >
> > However, I don't know how to implement s8_to_s64() here.
>
> Neither do I.
>
> > But at least the following code works (generates the same two-byte
> > machine code as ".byte 0x6a, vector" does):
> >
> > .if vector < 128
> > pushq $(vector)
> > .else
> > pushq $(0xffffffffffffff00+vector)
> > .endif
>
> Only slightly less ugly and needs as much commentry as the above.

Agree.

Just FYI, I tried this later, it can work.

#define S8_TO_S64(vector) ((vector>>7)*0xffffffffffffff00+vector)

Thanks
Lai