Re: [Xen-ia64-devel]PATCH] Remove duplicate check is_running_on_xen

[Alex Williamson <alex.williamson@xxxxxx>]

On Mon, 2007-01-15 at 13:33 +0800, Xu, Anthony wrote:
> 
> Remove duplicate check is_running_on_xen

Hi Anthony,

   I'm not sure I understand why the xen functions, for example
xen_get_psr(), need to support both bare metal and paravirtualized since
the caller always checks for is_running_on_xen.  The current code seems
overly paranoid.  Would is make more sense to rename these to
__xen_get_psr() and eliminate the running_on_xen check in the assembly?
Then we could still use the native bare metal calls when running a Xen
kernel on bare metal.  Am I missing some reason why xen_get_psr() would
ever get called on bare metal?  Thanks,

        Alex

> diff -r 29780963b34f linux-2.6-xen-sparse/arch/ia64/xen/hypercall.S
> --- a/linux-2.6-xen-sparse/arch/ia64/xen/hypercall.S    Mon Jan 15
> 04:27:37 2007 +0800
> +++ b/linux-2.6-xen-sparse/arch/ia64/xen/hypercall.S    Mon Jan 15
> 05:02:05 2007 +0800
> @@ -11,12 +11,9 @@ GLOBAL_ENTRY(xen_get_psr)
>  GLOBAL_ENTRY(xen_get_psr)
>         movl r8=running_on_xen;;
>         ld4 r8=[r8];;
> -       cmp.eq p7,p0=r8,r0;;
> -(p7)   mov r8=psr;;
> -(p7)   br.ret.sptk.many rp
> -       ;;
> -       XEN_HYPER_GET_PSR
> -       ;;
> +       cmp.eq p7,p6=r8,r0;;
> +(p7)   mov r8=psr
> +(p6)   XEN_HYPER_GET_PSR
>         br.ret.sptk.many rp
>         ;;
>  END(xen_get_psr)
...
>  linux-2.6-xen-sparse/include/asm-ia64/xen/privop.h
> --- a/linux-2.6-xen-sparse/include/asm-ia64/xen/privop.h        Mon
> Jan 15 04:27:37 2007 +0800
> +++ b/linux-2.6-xen-sparse/include/asm-ia64/xen/privop.h        Mon
> Jan 15 05:08:12 2007 +0800
> @@ -203,24 +203,16 @@ extern void xen_ptcga(unsigned long addr
>                                                                         \
>         switch(regnum)
> {                                                \
>         case
> _IA64_REG_PSR:                                             \
> -               ia64_intri_res =
> (is_running_on_xen()) ?                        \
> -                       xen_get_psr() :                                 \
> -                       __ia64_getreg(regnum);                          \
> +               ia64_intri_res =
> xen_get_psr();                                 \
>                 break;                                                  \

-- 
Alex Williamson                             HP Open Source & Linux Org.


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