Re: [Xen-devel] [PATCH 3/7] xen/mmu: Release the Xen provided L4 (PGD) back.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 26 Jul 2012, Konrad Rzeszutek Wilk wrote:
> Since we are not using it and somebody else could use it.

make sense except it is almost entirely rewritten by the following
patch...

> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
>  arch/x86/xen/mmu.c |   13 +++++++------
>  1 files changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index a59070b..48bdc9f 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -1782,20 +1782,21 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, 
> unsigned long max_pfn)
>       /* Unpin Xen-provided one */
>       pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
>  
> -     /* Switch over */
> -     pgd = init_level4_pgt;
> -
>       /*
>        * At this stage there can be no user pgd, and no page
>        * structure to attach it to, so make sure we just set kernel
>        * pgd.
>        */
>       xen_mc_batch();
> -     __xen_write_cr3(true, __pa(pgd));
> +     __xen_write_cr3(true, __pa(init_level4_pgt));
>       xen_mc_issue(PARAVIRT_LAZY_CPU);
>  
> -     memblock_reserve(__pa(xen_start_info->pt_base),
> -                      xen_start_info->nr_pt_frames * PAGE_SIZE);
> +     /* Offset by one page since the original pgd is going bye bye */
> +     memblock_reserve(__pa(xen_start_info->pt_base + PAGE_SIZE),
> +                      (xen_start_info->nr_pt_frames * PAGE_SIZE) - 
> PAGE_SIZE);
> +     /* and also RW it so it can actually be used. */
> +     set_page_prot(pgd, PAGE_KERNEL);
> +     clear_page(pgd);
>  }
>  #else        /* !CONFIG_X86_64 */
>  static RESERVE_BRK_ARRAY(pmd_t, initial_kernel_pmd, PTRS_PER_PMD);
> -- 
> 1.7.7.6
> 
> 
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> 

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