[Xen-devel] Re: [PATCH 14/16] paravirtualize IO permission bitmap

[Thomas Gleixner <tglx@xxxxxxxxxxxxx>]

On Tue, 12 May 2009, Jeremy Fitzhardinge wrote:

> From: Christophe Saout <chtephan@xxxxxxxxxxxxxxxxxxxx>
> 
> A PV Xen guest kernel has no TSS of its own, so the IO permission
> bitmap must be paravirtualized.  This patch adds set_io_bitmap
> as a paravirt op, and defines a native version which updates the tss,
> and a Xen version which uses a hypercall.
> 
> This is much easier now that 32 and 64-bit use the same code to
> manage the IO bitmap.

  Sigh, is there a plan to limit the paravirt horror at some point or
  are we keeping on adding to it forever ?

> --- a/arch/x86/kernel/ioport.c
> +++ b/arch/x86/kernel/ioport.c
> @@ -30,14 +30,31 @@ static void set_bitmap(unsigned long *bitmap, unsigned 
> int base,
>       }
>  }

This needs kernel doc annotation and a comment about the calling
conventions i.e. preemption disabled.
  
> +void native_set_io_bitmap(struct thread_struct *t,
> +                       int changed, unsigned long bytes_updated)
> +{
> +     struct tss_struct *tss;
> +
> +     if (!bytes_updated)
> +             return;
> +
> +     tss = &__get_cpu_var(init_tss);
> +
> +     /* Update the TSS: */
> +     if (t->io_bitmap_ptr)
> +             memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
> +     else
> +             memset(tss->io_bitmap, 0xff, bytes_updated);
> +}
> +

Thanks,

        tglx

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