iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Drivers: hv: balloon: Disable balloon and hot-add accordingly

Browse Source 
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@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20220325023212.1570049-3-boqun.feng@gmail.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
This commit is contained in:
Boqun Feng 2022-03-25 10:32:12 +08:00 committed by Wei Liu
parent b3d6dd09ff
commit be5802795c
1 changed files with 34 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
drivers/hv/hv_balloon.c
View File

@ -1660,6 +1660,38 @@ 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;
@ -1731,8 +1763,8 @@ 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