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

To: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH R4 2/7] xen/balloon: HVM mode support
From: Daniel Kiper <dkiper@xxxxxxxxxxxx>
Date: Tue, 15 Mar 2011 15:18:37 +0100
Cc: "jeremy@xxxxxxxx" <jeremy@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "haicheng.li@xxxxxxxxxxxxxxx" <haicheng.li@xxxxxxxxxxxxxxx>, "konrad.wilk@xxxxxxxxxx" <konrad.wilk@xxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "v.tolstov@xxxxxxxxx" <v.tolstov@xxxxxxxxx>, "dave@xxxxxxxxxxxxxxxxxx" <dave@xxxxxxxxxxxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>, "linux-mm@xxxxxxxxx" <linux-mm@xxxxxxxxx>, "rientjes@xxxxxxxxxx" <rientjes@xxxxxxxxxx>, "andi.kleen@xxxxxxxxx" <andi.kleen@xxxxxxxxx>, "akpm@xxxxxxxxxxxxxxxxxxxx" <akpm@xxxxxxxxxxxxxxxxxxxx>, "fengguang.wu@xxxxxxxxx" <fengguang.wu@xxxxxxxxx>, Daniel Kiper <dkiper@xxxxxxxxxxxx>, "wdauchy@xxxxxxxxx" <wdauchy@xxxxxxxxx>
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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)
-               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;


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