Currently there are known potential issues for balloon and hot-add on ARM64: * Unballoon requests from Hyper-V should only unballoon ranges that are guest page size aligned, otherwise guests cannot handle because it's impossible to partially free a page. * Memory hot-add requests from Hyper-V should provide the NUMA node id of the added ranges or ARM64 should have a functional memory_add_physaddr_to_nid(), otherwise the node id is missing for add_memory(). These issues require discussions on design and implementation. In the meanwhile, post_status() is working and essiential to guest monitoring. Therefore instead of the entire hv_balloon driver, the balloon and hot-add are disabled accordingly for now. Once the issues are fixed, they can be re-enable in these cases. Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx> --- drivers/hv/hv_balloon.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c index 062156b88a87..35dcda20be85 100644 --- a/drivers/hv/hv_balloon.c +++ b/drivers/hv/hv_balloon.c @@ -1730,9 +1730,19 @@ static int balloon_connect_vsp(struct hv_device *dev) * When hibernation (i.e. virtual ACPI S4 state) is enabled, the host * currently still requires the bits to be set, so we have to add code * to fail the host's hot-add and balloon up/down requests, if any. + * + * We disable balloon if the page size is larger than 4k, since + * currently it's unclear to us whether an unballoon request can make + * sure all page ranges are guest page size aligned. + * + * We also disable hot add on ARM64, because we currently rely on + * memory_add_physaddr_to_nid() to get a node id of a hot add range, + * however ARM64's memory_add_physaddr_to_nid() always return 0 and + * DM_MEM_HOT_ADD_REQUEST doesn't have the NUMA node information for + * add_memory(). */ - cap_msg.caps.cap_bits.balloon = 1; - cap_msg.caps.cap_bits.hot_add = 1; + cap_msg.caps.cap_bits.balloon = !(PAGE_SIZE > 4096UL); + cap_msg.caps.cap_bits.hot_add = !IS_ENABLED(CONFIG_ARM64); /* * Specify our alignment requirements as it relates -- 2.35.1
