The Hyper-V balloon driver installs a custom callback for handling page
onlining operations performed by the memory hotplug subsystem. This
custom callback is global, and overrides the default callback
(generic_online_page) that Linux otherwise uses. The custom callback
properly handles memory that is hot-added by the balloon driver as part
of a Hyper-V hot-add region.
But memory can also be hot-added directly by a device driver for a vPCI
device, particularly GPUs. In such a case, the custom callback installed by
the balloon driver runs, but won't find the page in its hot-add region list
and doesn't online it, which could cause driver initialization failures.
Fix this by having the balloon custom callback run generic_online_page()
when the page isn't part of a Hyper-V hot-add region, thereby doing the
default Linux behavior. This allows device driver hot-adds to work
properly. Similar cases are handled the same way in the virtio-mem driver.
Suggested-by: Vikram Sethi <vsethi@xxxxxxxxxx>
Tested-by: Michael Frohlich <mfrohlich@xxxxxxxxxxxxx>
Reviewed-by: Michael Kelley <mhklinux@xxxxxxxxxxx>
Signed-off-by: Jacob Pan <jacob.pan@xxxxxxxxxxxxxxxxxxx>
---
v2: Updated commit message suggested by Michael Kelley.
---
drivers/hv/hv_balloon.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index a99112e6f0b8..c999daf34108 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -766,16 +766,18 @@ static void hv_online_page(struct page *pg, unsigned int order)
struct hv_hotadd_state *has;
unsigned long pfn = page_to_pfn(pg);
- guard(spinlock_irqsave)(&dm_device.ha_lock);
- list_for_each_entry(has, &dm_device.ha_region_list, list) {
- /* The page belongs to a different HAS. */
- if (pfn < has->start_pfn ||
- (pfn + (1UL << order) > has->end_pfn))
- continue;
+ scoped_guard(spinlock_irqsave, &dm_device.ha_lock) {
+ list_for_each_entry(has, &dm_device.ha_region_list, list) {
+ /* The page belongs to a different HAS. */
+ if (pfn < has->start_pfn ||
+ (pfn + (1UL << order) > has->end_pfn))
+ continue;
- hv_bring_pgs_online(has, pfn, 1UL << order);
- break;
+ hv_bring_pgs_online(has, pfn, 1UL << order);
+ return;
+ }
}
+ generic_online_page(pg, order);
}
static int pfn_covered(unsigned long start_pfn, unsigned long pfn_cnt)
--
2.34.1
