[Xen-devel] Re: [PATCH R4 2/7] xen/balloon: HVM mode support

[Daniel Kiper <dkiper@xxxxxxxxxxxx>]

On Wed, Mar 09, 2011 at 01:58:30PM +0000, Stefano Stabellini wrote:
> On Tue, 8 Mar 2011, Daniel Kiper wrote:
> > HVM mode support.
>
> I have already a patch in linux-next to do this, please give a look at
> "xen: make the ballon driver work for hvm domains":
>
> git://xenbits.xen.org/people/sstabellini/linux-pvhvm.git linux-next

OK, I will remove this patch from memory hotplug patchset, however:

@@ -232,7 +232,7 @@ static int increase_reservation(unsigned long nr_pages)
                set_phys_to_machine(pfn, frame_list[i]);
 
                /* Link back into the page tables if not highmem. */
-               if (pfn < max_low_pfn) {
+               if (!xen_hvm_domain() && pfn < max_low_pfn) {

Why do not write it as:

if (xen_pv_domain() && !PageHighMem(page)) ...

For me it is simpler to read (xen_pv_domain()) and make it similar
to relevant part in decrease_reservation() (!PageHighMem(page)).

@@ -280,7 +280,7 @@ static int decrease_reservation(unsigned long nr_pages)
 
                scrub_page(page);
 
-               if (!PageHighMem(page)) {
+               if (!xen_hvm_domain() && !PageHighMem(page)) {

As above.

@@ -392,15 +392,19 @@ static struct notifier_block xenstore_notifier;
 
 static int __init balloon_init(void)
 {
-       unsigned long pfn, extra_pfn_end;
+       unsigned long pfn, nr_pages, extra_pfn_end;
        struct page *page;
 
-       if (!xen_pv_domain())
+       if (!xen_domain())
                return -ENODEV;
 
        pr_info("xen_balloon: Initialising balloon driver.\n");
 
-       balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn);
+       if (xen_pv_domain())
+               nr_pages = xen_start_info->nr_pages;
+       else
+               nr_pages = max_pfn;
+       balloon_stats.current_pages = min(nr_pages, max_pfn);

It could be simplified:

balloon_stats.current_pages = xen_pv_domain() ? min(xen_start_info->nr_pages, 
max_pfn) : max_pfn;

Daniel

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