Re: [Xen-devel] [PATCH 07/14] xen: balloon: do not update stage 1 pagetable for autotranslated guests

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 4 Oct 2012, Ian Campbell wrote:
> This is unnecessary (since the page will be removed from the p2m) and
> can be tricky if the page is in the middle of a superpage, as it is on
> ARM.
> 

I think that this patch is correct. I'll leave to Konrad whether we
should carry the original incorrect PVH patch and this separate fix or
just merge the two of them.


> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> ---
> Also effects PVH but in a benign way I think.
>
>  drivers/xen/balloon.c |   23 +++--------------------
>  1 files changed, 3 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index 7885a19..1b56ae0 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -357,15 +357,7 @@ static enum bp_state increase_reservation(unsigned long 
> nr_pages)
>               BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
>                      phys_to_machine_mapping_valid(pfn));
>  
> -             if (xen_pv_domain() && 
> -                 xen_feature(XENFEAT_auto_translated_physmap)) {
> -                     /* PVH: we just need to update native page table */
> -                     pte_t *ptep;
> -                     unsigned int level;
> -                     void *addr = __va(pfn << PAGE_SHIFT);
> -                     ptep = lookup_address((unsigned long)addr, &level);
> -                     set_pte(ptep, pfn_pte(pfn, PAGE_KERNEL));
> -             } else
> +             if (!xen_feature(XENFEAT_auto_translated_physmap))
>                       set_phys_to_machine(pfn, frame_list[i]);
>  
>               /* Link back into the page tables if not highmem. */
> @@ -427,21 +419,12 @@ static enum bp_state decrease_reservation(unsigned long 
> nr_pages, gfp_t gfp)
>  
>               scrub_page(page);
>  
> -             if (xen_pv_domain() && !PageHighMem(page)) {
> -                     if (xen_feature(XENFEAT_auto_translated_physmap)) {
> -                             unsigned int level;
> -                             pte_t *ptep;
> -                             void *addr = __va(pfn << PAGE_SHIFT);
> -                             ptep = lookup_address((unsigned long)addr, 
> -                                                     &level);
> -                             set_pte(ptep, __pte(0));
> -
> -                     } else {
> +             if (xen_pv_domain() && !PageHighMem(page) &&
> +                 !xen_feature(XENFEAT_auto_translated_physmap)) {
>                               ret = HYPERVISOR_update_va_mapping(
>                                       (unsigned long)__va(pfn << PAGE_SHIFT),
>                                       __pte_ma(0), 0);
>                               BUG_ON(ret);
> -                     }
>               }
>       }
>  
> -- 
> 1.7.2.5
> 

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