Re: [Xen-devel] [PATCH V2 6/7]: PVH: balloon and grant changes

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2012-10-11 at 23:01 +0100, Mukesh Rathor wrote:
> PVH: balloon and grant changes. For balloon changes we skip setting of
> local p2m as it's updated in xen. For grant, the shared grant frame is
> the pfn and not mfn, hence its mapped via the same code path as HVM
> 
> Signed-off-by: Mukesh R <mukesh.rathor@xxxxxxxxxx>
> ---
>  drivers/xen/balloon.c     |   18 +++++++++++-------
>  drivers/xen/gntdev.c      |    3 ++-
>  drivers/xen/grant-table.c |   25 +++++++++++++++++++++----
>  3 files changed, 34 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index 31ab82f..9b895ad 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -358,10 +358,13 @@ 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_feature(XENFEAT_auto_translated_physmap))
> +                     set_phys_to_machine(pfn, frame_list[i]);

set_phys_to_machine is a NOP if XENFEAT_auto_translated_physmap but it
includes some useful sanity checks (BUG_ON(pfn != mfn && mfn !=
INVALID_P2M_ENTRY)) so it would be useful to keep calling it I think.

>  
>               /* 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)) {
> +
>                       int ret;
>                       ret = HYPERVISOR_update_va_mapping(
>                               (unsigned long)__va(pfn << PAGE_SHIFT),
> @@ -418,12 +421,13 @@ 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)) {

You can combine this two ifs into one (like you did above).

> +                             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. */
> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> index 5df9fd8..36ec380 100644
> --- a/drivers/xen/gntdev.c
> +++ b/drivers/xen/gntdev.c
> @@ -803,7 +803,8 @@ 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);
>  
>       err = misc_register(&gntdev_miscdev);
>       if (err != 0) {
> @@ -1055,7 +1060,7 @@ static void gnttab_request_version(void)
>       int rc;
>       struct gnttab_set_version gsv;
>  
> -     if (xen_hvm_domain())
> +     if (xen_hvm_domain() || xen_feature(XENFEAT_auto_translated_physmap))

This is just a case of not yet implemented rather than a fundamental
problem with v2 grant tables, correct? (i.e. future work)

>               gsv.version = 1;
>       else
>               gsv.version = 2;
> @@ -1083,12 +1088,24 @@ static void gnttab_request_version(void)
>  int gnttab_resume(void)
>  {
>       unsigned int max_nr_gframes;
> +     char *kmsg = "Failed to kmalloc pages for pv in hvm grant frames\n";
>  
>       gnttab_request_version();
>       max_nr_gframes = gnttab_max_grant_frames();
>       if (max_nr_gframes < nr_grant_frames)
>               return -ENOSYS;
>  
> +     /* PVH note: xen will free existing kmalloc'd mfn in
> +      * XENMEM_add_to_physmap */

It doesn't leak it?

We should consider using xenballoon_alloc_pages here.

> +     if (xen_pv_domain() && xen_feature(XENFEAT_auto_translated_physmap) &&
> +         !gnttab_shared.addr) {
> +             gnttab_shared.addr =
> +                     kmalloc(max_nr_gframes * PAGE_SIZE, GFP_KERNEL);
> +             if (!gnttab_shared.addr) {
> +                     pr_warn("%s", kmsg);
> +                     return -ENOMEM;
> +             }
> +     }
>       if (xen_pv_domain())
>               return gnttab_map(0, nr_grant_frames - 1);
>  



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