The XEN balloon driver - in contrast to other balloon drivers - allows
to map some inflated pages to user space. Such pages are allocated via
alloc_xenballooned_pages() and freed via free_xenballooned_pages().
The pfn space of these allocated pages is used to map other things
by the hypervisor using hypercalls.
Pages marked with PG_offline must never be mapped to user space (as
this page type uses the mapcount field of struct pages).
So what we can do is, clear/set PG_offline when allocating/freeing an
inflated pages. This way, most inflated pages can be excluded by
dumping tools and the "reused for other purpose" balloon pages are
correctly not marked as PG_offline.
Fixes: 77c4adf6a6df (xen/balloon: mark inflated pages PG_offline)
Reported-by: Julien Grall <[email protected]>
Tested-by: Julien Grall <[email protected]>
Signed-off-by: David Hildenbrand <[email protected]>
---
drivers/xen/balloon.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 39b229f9e256..751d32f41f26 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -604,6 +604,7 @@ int alloc_xenballooned_pages(int nr_pages, struct page **pages)
while (pgno < nr_pages) {
page = balloon_retrieve(true);
if (page) {
+ __ClearPageOffline(page);
pages[pgno++] = page;
#ifdef CONFIG_XEN_HAVE_PVMMU
/*
@@ -646,6 +647,7 @@ void free_xenballooned_pages(int nr_pages, struct page **pages)
for (i = 0; i < nr_pages; i++) {
if (pages[i])
+ __SetPageOffline(pages[i]);
balloon_append(pages[i]);
}
--
2.17.2
On Thu, Mar 14, 2019 at 04:40:25PM +0100, David Hildenbrand wrote:
> @@ -646,6 +647,7 @@ void free_xenballooned_pages(int nr_pages, struct page **pages)
>
> for (i = 0; i < nr_pages; i++) {
> if (pages[i])
> + __SetPageOffline(pages[i]);
> balloon_append(pages[i]);
didn't you forget {} there? ;-)
> }
>
> --
> 2.17.2
>
--
Oscar Salvador
SUSE L3
>>> On 14.03.19 at 16:40, <[email protected]> wrote:
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -604,6 +604,7 @@ int alloc_xenballooned_pages(int nr_pages, struct page **pages)
> while (pgno < nr_pages) {
> page = balloon_retrieve(true);
> if (page) {
> + __ClearPageOffline(page);
> pages[pgno++] = page;
While this one's fine, ...
> @@ -646,6 +647,7 @@ void free_xenballooned_pages(int nr_pages, struct page **pages)
>
> for (i = 0; i < nr_pages; i++) {
> if (pages[i])
> + __SetPageOffline(pages[i]);
> balloon_append(pages[i]);
> }
... I think you want to add a pair of braces here.
Jan
On 14.03.19 16:49, Oscar Salvador wrote:
> On Thu, Mar 14, 2019 at 04:40:25PM +0100, David Hildenbrand wrote:
>> @@ -646,6 +647,7 @@ void free_xenballooned_pages(int nr_pages, struct page **pages)
>>
>> for (i = 0; i < nr_pages; i++) {
>> if (pages[i])
>> + __SetPageOffline(pages[i]);
>> balloon_append(pages[i]);
>
> didn't you forget {} there? ;-)
>
That's what happens when you stashed the original patch and try to
recreate it quickly from a mail ;)
Thanks!
--
Thanks,
David / dhildenb
On 14.03.19 16:49, Jan Beulich wrote:
>>>> On 14.03.19 at 16:40, <[email protected]> wrote:
>> --- a/drivers/xen/balloon.c
>> +++ b/drivers/xen/balloon.c
>> @@ -604,6 +604,7 @@ int alloc_xenballooned_pages(int nr_pages, struct page **pages)
>> while (pgno < nr_pages) {
>> page = balloon_retrieve(true);
>> if (page) {
>> + __ClearPageOffline(page);
>> pages[pgno++] = page;
>
> While this one's fine, ...
>
>> @@ -646,6 +647,7 @@ void free_xenballooned_pages(int nr_pages, struct page **pages)
>>
>> for (i = 0; i < nr_pages; i++) {
>> if (pages[i])
>> + __SetPageOffline(pages[i]);
>> balloon_append(pages[i]);
>> }
>
> ... I think you want to add a pair of braces here.
>
> Jan
>
>
Indeed, dropped by accident. Will resend in a minute. Thanks!
--
Thanks,
David / dhildenb