Coverity scan gives a warning when there is fall through in a switch
without a comment. This fall through is intentional as ol_waitevent needs
to be completed to unblock hv_mem_hot_add() allowing it to process next
requests regardless of the result of if we were able to online this block.
Reported-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Balloon driver was only printing the size of the info blob and not the
actual content. This fixes it so that the info blob (max page count as
configured in Hyper-V) is printed out.
Signed-off-by: Alex Ng <alexng@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
If the guest does not support memory hotplugging, it should respond to
the host with zero pages added and successful result code. This signals
to the host that hotplugging is not supported and the host will avoid
sending future hot-add requests.
Signed-off-by: Alex Ng <alexng@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reports for available memory should use the si_mem_available() value.
The previous freeram value does not include available page cache memory.
Signed-off-by: Alex Ng <alexng@messages.microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
lockdep reports possible circular locking dependency when udev is used
for memory onlining:
systemd-udevd/3996 is trying to acquire lock:
((memory_chain).rwsem){++++.+}, at: [<ffffffff810d137e>] __blocking_notifier_call_chain+0x4e/0xc0
but task is already holding lock:
(&dm_device.ha_region_mutex){+.+.+.}, at: [<ffffffffa015382e>] hv_memory_notifier+0x5e/0xc0 [hv_balloon]
...
which is probably a false positive because we take and release
ha_region_mutex from memory notifier chain depending on the arg. No real
deadlocks were reported so far (though I'm not really sure about
preemptible kernels...) but we don't really need to hold the mutex
for so long. We use it to protect ha_region_list (and its members) and the
num_pages_onlined counter. None of these operations require us to sleep
and nothing is slow, switch to using spinlock with interrupts disabled.
While on it, replace list_for_each -> list_for_each_entry as we actually
need entries in all these cases, drop meaningless list_empty() checks.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
With the recently introduced in-kernel memory onlining
(MEMORY_HOTPLUG_DEFAULT_ONLINE) these is no point in waiting for pages
to come online in the driver and we can get rid of the waiting.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
I'm observing the following hot add requests from the WS2012 host:
hot_add_req: start_pfn = 0x108200 count = 330752
hot_add_req: start_pfn = 0x158e00 count = 193536
hot_add_req: start_pfn = 0x188400 count = 239616
As the host doesn't specify hot add regions we're trying to create
128Mb-aligned region covering the first request, we create the 0x108000 -
0x160000 region and we add 0x108000 - 0x158e00 memory. The second request
passes the pfn_covered() check, we enlarge the region to 0x108000 -
0x190000 and add 0x158e00 - 0x188200 memory. The problem emerges with the
third request as it starts at 0x188400 so there is a 0x200 gap which is
not covered. As the end of our region is 0x190000 now it again passes the
pfn_covered() check were we just adjust the covered_end_pfn and make it
0x188400 instead of 0x188200 which means that we'll try to online
0x188200-0x188400 pages but these pages were never assigned to us and we
crash.
We can't react to such requests by creating new hot add regions as it may
happen that the whole suggested range falls into the previously identified
128Mb-aligned area so we'll end up adding nothing or create intersecting
regions and our current logic doesn't allow that. Instead, create a list of
such 'gaps' and check for them in the page online callback.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Windows 2012 (non-R2) does not specify hot add region in hot add requests
and the logic in hot_add_req() is trying to find a 128Mb-aligned region
covering the request. It may also happen that host's requests are not 128Mb
aligned and the created ha_region will start before the first specified
PFN. We can't online these non-present pages but we don't remember the real
start of the region.
This is a regression introduced by the commit 5abbbb75d7 ("Drivers: hv:
hv_balloon: don't lose memory when onlining order is not natural"). While
the idea of keeping the 'moving window' was wrong (as there is no guarantee
that hot add requests come ordered) we should still keep track of
covered_start_pfn. This is not a revert, the logic is different.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We set host_specified_ha_region = true on certain request but this is a
global state which stays 'true' forever. We need to reset it when we
receive a request where ha_region is not specified. I did not see any
real issues, the bug was found by code inspection.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When we iterate through all HA regions in handle_pg_range() we have an
assumption that all these regions are sorted in the list and the
'start_pfn >= has->end_pfn' check is enough to find the proper region.
Unfortunately it's not the case with WS2016 where host can hot-add regions
in a different order. We end up modifying the wrong HA region and crashing
later on pages online. Modify the check to make sure we found the region
we were searching for while iterating. Fix the same check in pfn_covered()
as well.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Support Win10 protocol for Dynamic Memory. Thia patch allows guests on Win10 hosts
to hot-add memory even when dynamic memory is not enabled on the guest.
Signed-off-by: Alex Ng <alexng@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Memory notifiers are being executed in a sequential order and when one of
them fails returning something different from NOTIFY_OK the remainder of
the notification chain is not being executed. When a memory block is being
onlined in online_pages() we do memory_notify(MEM_GOING_ONLINE, ) and if
one of the notifiers in the chain fails we end up doing
memory_notify(MEM_CANCEL_ONLINE, ) so it is possible for a notifier to see
MEM_CANCEL_ONLINE without seeing the corresponding MEM_GOING_ONLINE event.
E.g. when CONFIG_KASAN is enabled the kasan_mem_notifier() is being used
to prevent memory hotplug, it returns NOTIFY_BAD for all MEM_GOING_ONLINE
events. As kasan_mem_notifier() comes before the hv_memory_notifier() in
the notification chain we don't see the MEM_GOING_ONLINE event and we do
not take the ha_region_mutex. We, however, see the MEM_CANCEL_ONLINE event
and unconditionally try to release the lock, the following is observed:
[ 110.850927] =====================================
[ 110.850927] [ BUG: bad unlock balance detected! ]
[ 110.850927] 4.1.0-rc3_bugxxxxxxx_test_xxxx #595 Not tainted
[ 110.850927] -------------------------------------
[ 110.850927] systemd-udevd/920 is trying to release lock
(&dm_device.ha_region_mutex) at:
[ 110.850927] [<ffffffff81acda0e>] mutex_unlock+0xe/0x10
[ 110.850927] but there are no more locks to release!
At the same time we can have the ha_region_mutex taken when we get the
MEM_CANCEL_ONLINE event in case one of the memory notifiers after the
hv_memory_notifier() in the notification chain failed so we need to add
the mutex_is_locked() check. In case of MEM_ONLINE we are always supposed
to have the mutex locked.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
balloon_wrk.num_pages is __u32 and it comes from host in struct dm_balloon
where it is also __u32. We, however, use 'int' in balloon_up() and in case
we happen to receive num_pages>INT_MAX request we'll end up allocating zero
pages as 'num_pages < alloc_unit' check in alloc_balloon_pages() will pass.
Change num_pages type to unsigned int.
In real life ballooning request come with num_pages in [512, 32768] range so
this is more a future-proof/cleanup.
Reported-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
'Drivers: hv: hv_balloon: refuse to balloon below the floor' fix does not
correctly handle the case when val.freeram < num_pages as val.freeram is
__kernel_ulong_t and the 'val.freeram - num_pages' value will be a huge
positive value instead of being negative.
Usually host doesn't ask us to balloon more than val.freeram but in case
he have a memory hog started after we post the last pressure report we
can get into troubles.
Suggested-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
... and simplify alloc_balloon_pages() interface by removing redundant
alloc_error from it.
If we happen to enter balloon_up() with balloon_wrk.num_pages = 0 we will enter
infinite 'while (!done)' loop as alloc_balloon_pages() will be always returning
0 and not setting alloc_error. We will also be sending a meaningless message to
the host on every iteration.
The 'alloc_unit == 1 && alloc_error -> num_ballooned == 0' change and
alloc_error elimination requires a special comment. We do alloc_balloon_pages()
with 2 different alloc_unit values and there are 4 different
alloc_balloon_pages() results, let's check them all.
alloc_unit = 512:
1) num_ballooned = 0, alloc_error = 0: we do 'alloc_unit=1' and retry pre- and
post-patch.
2) num_ballooned > 0, alloc_error = 0: we check 'num_ballooned == num_pages'
and act accordingly, pre- and post-patch.
3) num_ballooned > 0, alloc_error > 0: we report this chunk and remain within
the loop, no changes here.
4) num_ballooned = 0, alloc_error > 0: we do 'alloc_unit=1' and retry pre- and
post-patch.
alloc_unit = 1:
1) num_ballooned = 0, alloc_error = 0: this can happen in two cases: when we
passed 'num_pages=0' to alloc_balloon_pages() or when there was no space in
bl_resp to place a single response. The second option is not possible as
bl_resp is of PAGE_SIZE size and single response 'union dm_mem_page_range' is
8 bytes, but the first one is (in theory, I think that Hyper-V host never
places such requests). Pre-patch code loops forever, post-patch code sends
a reply with more_pages = 0 and finishes.
2) num_ballooned > 0, alloc_error = 0: we ran out of space in bl_resp, we
report partial success and remain within the loop, no changes pre- and
post-patch.
3) num_ballooned > 0, alloc_error > 0: pre-patch code finishes, post-patch code
does one more try and if there is no progress (we finish with
'num_ballooned = 0') we finish. So we try a bit harder with this patch.
4) num_ballooned = 0, alloc_error > 0: both pre- and post-patch code enter
'more_pages = 0' branch and finish.
So this patch has two real effects:
1) We reply with an empty response to 'num_pages=0' request.
2) We try a bit harder on alloc_unit=1 allocations (and reply with an empty
tail reply in case we fail).
An empty reply should be supported by host as we were able to send it even with
pre-patch code when we were not able to allocate a single page.
Suggested-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit 79208c57da ("Drivers: hv: hv_balloon: Make adjustments in computing
the floor") was inacurate as it introduced a jump in our piecewiese linear
'floor' function:
At 2048MB we have:
Left limit:
104 + 2048/8 = 360
Right limit:
256 + 2048/16 = 384 (so the right value is 232)
We now have to make an adjustment at 8192 boundary:
232 + 8192/16 = 744
512 + 8192/32 = 768 (so the right value is 488)
Suggested-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Currently we add memory in 128Mb blocks but the request from host can be
aligned differently. In such case we add a partially backed block and
when this block goes online we skip onlining pages which are not backed
(hv_online_page() callback serves this purpose). When we receive next
request for the same host add region we online pages which were not backed
before with hv_bring_pgs_online(). However, we don't check if the the block
in question was onlined and online this tail unconditionally. This is bad as
we avoid all online_pages() logic: these pages are not accounted, we don't
send notifications (and hv_balloon is not the only receiver of them),...
And, first of all, nobody asked as to online these pages. Solve the issue by
checking if the last previously backed page was onlined and onlining the tail
only in case it was.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Memory blocks can be onlined in random order. When this order is not natural
some memory pages are not onlined because of the redundant check in
hv_online_page().
Here is a real world scenario:
1) Host tries to hot-add the following (process_hot_add):
pg_start=rg_start=0x48000, pfn_cnt=111616, rg_size=262144
2) This results in adding 4 memory blocks:
[ 109.057866] init_memory_mapping: [mem 0x48000000-0x4fffffff]
[ 114.102698] init_memory_mapping: [mem 0x50000000-0x57ffffff]
[ 119.168039] init_memory_mapping: [mem 0x58000000-0x5fffffff]
[ 124.233053] init_memory_mapping: [mem 0x60000000-0x67ffffff]
The last one is incomplete but we have special has->covered_end_pfn counter to
avoid onlining non-backed frames and hv_bring_pgs_online() function to bring
them online later on.
3) Now we have 4 offline memory blocks: /sys/devices/system/memory/memory9-12
$ for f in /sys/devices/system/memory/memory*/state; do echo $f `cat $f`; done | grep -v onlin
/sys/devices/system/memory/memory10/state offline
/sys/devices/system/memory/memory11/state offline
/sys/devices/system/memory/memory12/state offline
/sys/devices/system/memory/memory9/state offline
4) We bring them online in non-natural order:
$grep MemTotal /proc/meminfo
MemTotal: 966348 kB
$echo online > /sys/devices/system/memory/memory12/state && grep MemTotal /proc/meminfo
MemTotal: 1019596 kB
$echo online > /sys/devices/system/memory/memory11/state && grep MemTotal /proc/meminfo
MemTotal: 1150668 kB
$echo online > /sys/devices/system/memory/memory9/state && grep MemTotal /proc/meminfo
MemTotal: 1150668 kB
As you can see memory9 block gives us zero additional memory. We can also
observe a huge discrepancy between host- and guest-reported memory sizes.
The root cause of the issue is the redundant pg >= covered_start_pfn check (and
covered_start_pfn advancing) in hv_online_page(). When upper memory block in
being onlined before the lower one (memory12 and memory11 in the above case) we
advance the covered_start_pfn pointer and all memory9 pages do not pass the
check. If the assumption that host always gives us requests in sequential order
and pg_start always equals rg_start when the first request for the new HA
region is received (that's the case in my testing) is correct than we can get
rid of covered_start_pfn and pg >= start_pfn check in hv_online_page() is
sufficient.
The current char-next branch is broken and this patch fixes
the bug.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When add_memory() fails the following BUG is observed:
[ 743.646107] hv_balloon: hot_add memory failed error is -17
[ 743.679973]
[ 743.680930] =====================================
[ 743.680930] [ BUG: bad unlock balance detected! ]
[ 743.680930] 3.19.0-rc5_bug1131426+ #552 Not tainted
[ 743.680930] -------------------------------------
[ 743.680930] kworker/0:2/255 is trying to release lock (&dm_device.ha_region_mutex) at:
[ 743.680930] [<ffffffff81aae5fe>] mutex_unlock+0xe/0x10
[ 743.680930] but there are no more locks to release!
This happens as we don't acquire ha_region_mutex and hot_add_req() expects us
to as it does unconditional mutex_unlock(). Acquire the lock on the error path.
The current char-next branch is broken and this patch fixes
the bug.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When host asks us to balloon up we need to be sure we're not committing suicide
by overballooning. Use already existent 'floor' metric as our lowest possible
value for free ram.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When hot-added memory pages are not brought online or when some memory blocks
are sent offline the subsequent ballooning process kills the guest with OOM
killer. This happens as we don't report these pages as neither used nor free
and apparently host algorithm considers them as being unused. Keep track of
all online/offline operations and report all currently offline pages as being
used so host won't try to balloon them out.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When many memory regions are being added and automatically onlined the
following lockup is sometimes observed:
INFO: task udevd:1872 blocked for more than 120 seconds.
...
Call Trace:
[<ffffffff816ec0bc>] schedule_timeout+0x22c/0x350
[<ffffffff816eb98f>] wait_for_common+0x10f/0x160
[<ffffffff81067650>] ? default_wake_function+0x0/0x20
[<ffffffff816eb9fd>] wait_for_completion+0x1d/0x20
[<ffffffff8144cb9c>] hv_memory_notifier+0xdc/0x120
[<ffffffff816f298c>] notifier_call_chain+0x4c/0x70
...
When several memory blocks are going online simultaneously we got several
hv_memory_notifier() trying to acquire the ha_region_mutex. When this mutex is
being held by hot_add_req() all these competing acquire_region_mutex() do
mutex_trylock, fail, and queue themselves into wait_for_completion(..). However
when we do complete() from release_region_mutex() only one of them wakes up.
This could be solved by changing complete() -> complete_all() memory onlining
can be delayed as well, in that case we can still get several
hv_memory_notifier() runners at the same time trying to grab the mutex.
Only one of them will succeed and the others will hang for forever as
complete() is not being called. We don't see this issue often because we have
5sec onlining timeout in hv_mem_hot_add() and usually all udev events arrive
in this time frame.
Get rid of the trylock path, waiting on the mutex is supposed to provide the
required serialization.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
return type of wait_for_completion_timeout is unsigned long not int, this
patch changes the type of t from int to unsigned long.
Signed-off-by: Nicholas Mc Guire <der.herr@hofr.at>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stephen Hemminger
Vitaly Kuznetsov
Alex Ng
Alex Ng
Nicholas Mc Guire