On 11.03.24 19:12, mhkelley58@xxxxxxxxx wrote:
From: Michael Kelley <mhklinux@xxxxxxxxxxx>
The Hyper-V balloon driver supports hot-add of memory in addition
to ballooning. Current code hot-adds in fixed size chunks of
128 Mbytes (fixed constant HA_CHUNK in the code). While this works
in Hyper-V VMs with 64 Gbytes or less or memory where the Linux
memblock size is 128 Mbytes, the hot-add fails for larger memblock
sizes because add_memory() expects memory to be added in chunks
that match the memblock size. Messages like the following are
reported when Linux has a 256 Mbyte memblock size:
[ 312.668859] Block size [0x10000000] unaligned hotplug range:
start 0x310000000, size 0x8000000
[ 312.668880] hv_balloon: hot_add memory failed error is -22
[ 312.668984] hv_balloon: Memory hot add failed
Larger memblock sizes are usually used in VMs with more than
64 Gbytes of memory, depending on the alignment of the VM's
physical address space.
Right, that's the case since 2018.
Fix this problem by having the Hyper-V balloon driver determine
the Linux memblock size, and process hot-add requests in that
chunk size instead of a fixed 128 Mbytes. Also update the hot-add
alignment requested of the Hyper-V host to match the memblock
size instead of being a fixed 128 Mbytes.
That way, we should never be getting unaligned ranges IIRC, correct? I
think we added ways in QEMU to guarantee that for the HV-balloon
implementation as well.
The code changes look significant, but in fact are just a
Nah, it's okay :)
simple text substitution of a new global variable for the
previous HA_CHUNK constant. No algorithms are changed except
to initialize the new global variable and to calculate the
alignment value to pass to Hyper-V. Testing with memblock
sizes of 256 Mbytes and 2 Gbytes shows correct operation.
Signed-off-by: Michael Kelley <mhklinux@xxxxxxxxxxx>
---
drivers/hv/hv_balloon.c | 64 ++++++++++++++++++++++++-----------------
1 file changed, 37 insertions(+), 27 deletions(-)
diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index e000fa3b9f97..d3bfbf3d274a 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -425,11 +425,11 @@ struct dm_info_msg {
* The range start_pfn : end_pfn specifies the range
* that the host has asked us to hot add. The range
* start_pfn : ha_end_pfn specifies the range that we have
- * currently hot added. We hot add in multiples of 128M
- * chunks; it is possible that we may not be able to bring
- * online all the pages in the region. The range
+ * currently hot added. We hot add in chunks equal to the
+ * memory block size; it is possible that we may not be able
+ * to bring online all the pages in the region. The range
* covered_start_pfn:covered_end_pfn defines the pages that can
- * be brough online.
+ * be brought online.
*/
struct hv_hotadd_state {
@@ -505,8 +505,9 @@ enum hv_dm_state {
static __u8 recv_buffer[HV_HYP_PAGE_SIZE];
static __u8 balloon_up_send_buffer[HV_HYP_PAGE_SIZE];
+static unsigned long ha_chunk_pgs;
Why not stick to PAGES_IN_2M and call this
ha_pages_in_chunk? Much easier to get than "pgs".
Apart from that looks good. Some helper macros to convert size to chunks
etc. might make the code even more readable.
--
Cheers,
David / dhildenb
