Re: [Xen-devel] [PATCH v1 6/8]: PVH ballooning and grant changes

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-09-21 at 20:19 +0100, Mukesh Rathor wrote:
> ---
>  drivers/xen/balloon.c     |   35 ++++++++++++++++++++++++++++-------
>  drivers/xen/gntdev.c      |    3 ++-
>  drivers/xen/grant-table.c |   25 +++++++++++++++++++++----
>  3 files changed, 51 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index 31ab82f..85a6917 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -358,10 +358,21 @@ static enum bp_state increase_reservation(unsigned long 
> nr_pages)
>               BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
>                      phys_to_machine_mapping_valid(pfn));
>  
> -             set_phys_to_machine(pfn, frame_list[i]);
> +             if (xen_pv_domain() && 
> +                 xen_feature(XENFEAT_auto_translated_physmap)) {
> +                     /* PVH: we just need to update native page table */

Do you not need a PageHighMem check here somewhere? (although this is
moot if you follow the suggestion below)

> +                     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
> +                     set_phys_to_machine(pfn, frame_list[i]);
>  
>               /* Link back into the page tables if not highmem. */
> -             if (xen_pv_domain() && !PageHighMem(page)) {
> +             if (xen_pv_domain() && !PageHighMem(page) && 
> +                 !xen_feature(XENFEAT_auto_translated_physmap)) {

I think it would be more logical to put the PVH PT update here next to
the PV PT update and gate the set_phys_to_machine above on !a_t_pm, like
how you've done it in the decrease case.

(or perhaps per your comment below set_phys_to_machine isa NOP also on
PVH?)

> +
>                       int ret;
>                       ret = HYPERVISOR_update_va_mapping(
>                               (unsigned long)__va(pfn << PAGE_SHIFT),
> @@ -418,12 +429,21 @@ static enum bp_state decrease_reservation(unsigned long 
> nr_pages, gfp_t gfp)
>               scrub_page(page);
>  
>               if (xen_pv_domain() && !PageHighMem(page)) {
> -                     ret = HYPERVISOR_update_va_mapping(
> -                             (unsigned long)__va(pfn << PAGE_SHIFT),
> -                             __pte_ma(0), 0);
> -                     BUG_ON(ret);
> +                     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 {
> +                             ret = HYPERVISOR_update_va_mapping(
> +                                     (unsigned long)__va(pfn << PAGE_SHIFT),
> +                                     __pte_ma(0), 0);
> +                             BUG_ON(ret);
> +                     }
>               }
> -
>       }
>  
>       /* Ensure that ballooned highmem pages don't have kmaps. */
> @@ -433,6 +453,7 @@ static enum bp_state decrease_reservation(unsigned long 
> nr_pages, gfp_t gfp)
>       /* No more mappings: invalidate P2M and add to balloon. */
>       for (i = 0; i < nr_pages; i++) {
>               pfn = mfn_to_pfn(frame_list[i]);
> +             /* PVH note: following will noop for auto translated */
>               __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
>               balloon_append(pfn_to_page(pfn));
>       }
> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> index 1ffd03b..35d1e3c 100644
> --- a/drivers/xen/gntdev.c
> +++ b/drivers/xen/gntdev.c
> @@ -802,7 +802,8 @@ static int __init gntdev_init(void)
>       if (!xen_domain())
>               return -ENODEV;
>  
> -     use_ptemod = xen_pv_domain();
> +     use_ptemod = xen_pv_domain() && 
> +                  !xen_feature(XENFEAT_auto_translated_physmap);

I keep wondering if
#define XENFEAT(x) xen_feature(XENFEAT_#x)
might not be useful to keep some of these long lines under control.

Probably not, since the bulk is the "x" bit...

Ian.



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