linux-kernel - Re: [PATCH 14/16] paravirtualize IO permission bitmap

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Date:	Tue, 2 Jun 2009 18:11:04 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
cc:	Ingo Molnar <mingo@...e.hu>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Xen-devel <xen-devel@...ts.xensource.com>,
	Christophe Saout <chtephan@...o.intern.saout.de>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: Re: [PATCH 14/16] paravirtualize IO permission bitmap

On Tue, 12 May 2009, Jeremy Fitzhardinge wrote:

> From: Christophe Saout <chtephan@...o.intern.saout.de>
> 
> 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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