4.9-stable review patch. If anyone has any objections, please let me know.
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From: Nadav Amit namit@vmware.com
commit 5081efd112560d3febb328e627176235b250d59d upstream.
If the hypervisor sets 2MB batching is on, while batching is cleared, the balloon code breaks. In this case the legacy mechanism is used with 2MB page. The VM would report a 2MB page is ballooned, and the hypervisor would only take the first 4KB.
While the hypervisor should not report such settings, make the code more robust by not enabling 2MB support without batching.
Fixes: 365bd7ef7ec8e ("VMware balloon: Support 2m page ballooning.") Cc: stable@vger.kernel.org Reviewed-by: Xavier Deguillard xdeguillard@vmware.com Signed-off-by: Nadav Amit nadav.amit@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/misc/vmw_balloon.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
--- a/drivers/misc/vmw_balloon.c +++ b/drivers/misc/vmw_balloon.c @@ -341,7 +341,13 @@ static bool vmballoon_send_start(struct success = false; }
- if (b->capabilities & VMW_BALLOON_BATCHED_2M_CMDS) + /* + * 2MB pages are only supported with batching. If batching is for some + * reason disabled, do not use 2MB pages, since otherwise the legacy + * mechanism is used with 2MB pages, causing a failure. + */ + if ((b->capabilities & VMW_BALLOON_BATCHED_2M_CMDS) && + (b->capabilities & VMW_BALLOON_BATCHED_CMDS)) b->supported_page_sizes = 2; else b->supported_page_sizes = 1;