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hv_balloon: Fallback to generic_online_page() for non-HV hot added mem

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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@nvidia.com>
Tested-by: Michael Frohlich <mfrohlich@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Jacob Pan <jacob.pan@linux.microsoft.com>
Link: https://lore.kernel.org/r/20250107180918.1053933-1-jacob.pan@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20250107180918.1053933-1-jacob.pan@linux.microsoft.com>
This commit is contained in:
Jacob Pan 2025-01-07 10:09:18 -08:00 • committed by Wei Liu
parent fcf5203e28
commit 1da602ec36
1 changed files with 10 additions and 8 deletions
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18
drivers/hv/hv_balloon.c
View file

@ -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)