From: Boqun Feng <boqun.feng@xxxxxxxxx> [ Upstream commit be5802795cf8d0b881745fa9ba7790293b382280 ] 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. This is a problem when guest page size > 4096 bytes. * 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 essential to guest monitoring. Therefore instead of disabling the entire hv_balloon driver, the ballooning (when page size > 4096 bytes) 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> Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20220325023212.1570049-3-boqun.feng@xxxxxxxxx Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/hv/hv_balloon.c | 36 ++++++++++++++++++++++++++++++++++-- 1 file changed, 34 insertions(+), 2 deletions(-) diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c index 439f99b8b5de..3cf334c46c31 100644 --- a/drivers/hv/hv_balloon.c +++ b/drivers/hv/hv_balloon.c @@ -1653,6 +1653,38 @@ static void disable_page_reporting(void) } } +static int ballooning_enabled(void) +{ + /* + * Disable ballooning if the page size is not 4k (HV_HYP_PAGE_SIZE), + * since currently it's unclear to us whether an unballoon request can + * make sure all page ranges are guest page size aligned. + */ + if (PAGE_SIZE != HV_HYP_PAGE_SIZE) { + pr_info("Ballooning disabled because page size is not 4096 bytes\n"); + return 0; + } + + return 1; +} + +static int hot_add_enabled(void) +{ + /* + * 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(). + */ + if (IS_ENABLED(CONFIG_ARM64)) { + pr_info("Memory hot add disabled on ARM64\n"); + return 0; + } + + return 1; +} + static int balloon_connect_vsp(struct hv_device *dev) { struct dm_version_request version_req; @@ -1724,8 +1756,8 @@ static int balloon_connect_vsp(struct hv_device *dev) * 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. */ - cap_msg.caps.cap_bits.balloon = 1; - cap_msg.caps.cap_bits.hot_add = 1; + cap_msg.caps.cap_bits.balloon = ballooning_enabled(); + cap_msg.caps.cap_bits.hot_add = hot_add_enabled(); /* * Specify our alignment requirements as it relates -- 2.35.1
