Re: [PATCH] xen/SandyBridge: reserve pages when integrated graphics

["Jan Beulich" <JBeulich@suse.com>]

>>> On 22.03.13 at 08:48, Xudong Hao <xudong.hao@intel.com> wrote:
> +char *__init get_platform_badpages(void)
> +{
> +    u32 igd_id;
> +    static char __initdata bad_pfns[] = 
> +                {"0x20050,0x20110,0x20130,0x20138,0x40004"};

With quite a bit of trouble I managed to find all applicable spec
updates, but none of them mentions 0x20110.

> +#ifdef CONFIG_X86
> +    /* 
> +     * Here we put platform-specific memory range workarounds, i.e.
> +     * memory known to be corrupt or otherwise in need to be reserved on
> +     * specific platforms.
> +     * We get these certain pages and put them in bad-page list.
> +     */
> +    p = get_platform_badpages();
> +    if ( p )
> +        remove_bad_pages(p);
> +#endif

I also dislike the re-use of the command line parsing code here.
There's no need to do this for a list of known MFNs, the hook
could provide an array of unsigned long instead.

And finally it is my understanding that these pages aren't bad in
any way, it must only be ensured they don't get passed to the
graphics engine. Which in particular means using these pages for
Xen's own purposes (i.e. not passing them to any domain) would
be quite fine. Yes, I realize it's only a handful of pages, but it
seems odd anyway.

Jan