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virtio-mem: Big Block Mode (BBM) - basic memory hotunplug

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Let's try to unplug completely offline big blocks first. Then, (if
enabled via unplug_offline) try to offline and remove whole big blocks.

No locking necessary - we can deal with concurrent onlining/offlining
just fine.

Note1: This is sub-optimal and might be dangerous in some environments: we
could end up in an infinite loop when offlining (e.g., long-term pinnings),
similar as with DIMMs. We'll introduce safe memory hotunplug via
fake-offlining next, and use this basic mode only when explicitly enabled.

Note2: Without ZONE_MOVABLE, memory unplug will be extremely unreliable
with bigger block sizes.

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20201112133815.13332-29-david@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
David Hildenbrand 2020-11-12 14:38:14 +01:00 committed by Michael S. Tsirkin
parent 8dc4bb58a1
commit 269ac9389d
1 changed files with 155 additions and 1 deletions
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156
drivers/virtio/virtio_mem.c
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@ -390,6 +390,12 @@ static int virtio_mem_bbm_bb_states_prepare_next_bb(struct virtio_mem *vm)
_bb_id++) \
if (virtio_mem_bbm_get_bb_state(_vm, _bb_id) == _state)
#define virtio_mem_bbm_for_each_bb_rev(_vm, _bb_id, _state) \
for (_bb_id = vm->bbm.next_bb_id - 1; \
_bb_id >= vm->bbm.first_bb_id && _vm->bbm.bb_count[_state]; \
_bb_id--) \
if (virtio_mem_bbm_get_bb_state(_vm, _bb_id) == _state)
/*
* Set the state of a memory block, taking care of the state counter.
*/
@ -685,6 +691,18 @@ static int virtio_mem_sbm_remove_mb(struct virtio_mem *vm, unsigned long mb_id)
return virtio_mem_remove_memory(vm, addr, size);
}
/*
* See virtio_mem_remove_memory(): Try to remove all Linux memory blocks covered
* by the big block.
*/
static int virtio_mem_bbm_remove_bb(struct virtio_mem *vm, unsigned long bb_id)
{
const uint64_t addr = virtio_mem_bb_id_to_phys(vm, bb_id);
const uint64_t size = vm->bbm.bb_size;
return virtio_mem_remove_memory(vm, addr, size);
}
/*
* Try offlining and removing memory from Linux.
*
@ -731,6 +749,19 @@ static int virtio_mem_sbm_offline_and_remove_mb(struct virtio_mem *vm,
return virtio_mem_offline_and_remove_memory(vm, addr, size);
}
/*
* See virtio_mem_offline_and_remove_memory(): Try to offline and remove a
* all Linux memory blocks covered by the big block.
*/
static int virtio_mem_bbm_offline_and_remove_bb(struct virtio_mem *vm,
unsigned long bb_id)
{
const uint64_t addr = virtio_mem_bb_id_to_phys(vm, bb_id);
const uint64_t size = vm->bbm.bb_size;
return virtio_mem_offline_and_remove_memory(vm, addr, size);
}
/*
* Trigger the workqueue so the device can perform its magic.
*/
@ -1928,6 +1959,129 @@ out_unlock:
return rc;
}
/*
* Try to offline and remove a big block from Linux and unplug it. Will fail
* with -EBUSY if some memory is busy and cannot get unplugged.
*
* Will modify the state of the memory block. Might temporarily drop the
* hotplug_mutex.
*/
static int virtio_mem_bbm_offline_remove_and_unplug_bb(struct virtio_mem *vm,
unsigned long bb_id)
{
int rc;
if (WARN_ON_ONCE(virtio_mem_bbm_get_bb_state(vm, bb_id) !=
VIRTIO_MEM_BBM_BB_ADDED))
return -EINVAL;
rc = virtio_mem_bbm_offline_and_remove_bb(vm, bb_id);
if (rc)
return rc;
rc = virtio_mem_bbm_unplug_bb(vm, bb_id);
if (rc)
virtio_mem_bbm_set_bb_state(vm, bb_id,
VIRTIO_MEM_BBM_BB_PLUGGED);
else
virtio_mem_bbm_set_bb_state(vm, bb_id,
VIRTIO_MEM_BBM_BB_UNUSED);
return rc;
}
/*
* Try to remove a big block from Linux and unplug it. Will fail with
* -EBUSY if some memory is online.
*
* Will modify the state of the memory block.
*/
static int virtio_mem_bbm_remove_and_unplug_bb(struct virtio_mem *vm,
unsigned long bb_id)
{
int rc;
if (WARN_ON_ONCE(virtio_mem_bbm_get_bb_state(vm, bb_id) !=
VIRTIO_MEM_BBM_BB_ADDED))
return -EINVAL;
rc = virtio_mem_bbm_remove_bb(vm, bb_id);
if (rc)
return -EBUSY;
rc = virtio_mem_bbm_unplug_bb(vm, bb_id);
if (rc)
virtio_mem_bbm_set_bb_state(vm, bb_id,
VIRTIO_MEM_BBM_BB_PLUGGED);
else
virtio_mem_bbm_set_bb_state(vm, bb_id,
VIRTIO_MEM_BBM_BB_UNUSED);
return rc;
}
/*
* Test if a big block is completely offline.
*/
static bool virtio_mem_bbm_bb_is_offline(struct virtio_mem *vm,
unsigned long bb_id)
{
const unsigned long start_pfn = PFN_DOWN(virtio_mem_bb_id_to_phys(vm, bb_id));
const unsigned long nr_pages = PFN_DOWN(vm->bbm.bb_size);
unsigned long pfn;
for (pfn = start_pfn; pfn < start_pfn + nr_pages;
pfn += PAGES_PER_SECTION) {
if (pfn_to_online_page(pfn))
return false;
}
return true;
}
static int virtio_mem_bbm_unplug_request(struct virtio_mem *vm, uint64_t diff)
{
uint64_t nb_bb = diff / vm->bbm.bb_size;
uint64_t bb_id;
int rc;
if (!nb_bb)
return 0;
/* Try to unplug completely offline big blocks first. */
virtio_mem_bbm_for_each_bb_rev(vm, bb_id, VIRTIO_MEM_BBM_BB_ADDED) {
cond_resched();
/*
* As we're holding no locks, this check is racy as memory
* can get onlined in the meantime - but we'll fail gracefully.
*/
if (!virtio_mem_bbm_bb_is_offline(vm, bb_id))
continue;
rc = virtio_mem_bbm_remove_and_unplug_bb(vm, bb_id);
if (rc == -EBUSY)
continue;
if (!rc)
nb_bb--;
if (rc || !nb_bb)
return rc;
}
if (!unplug_online)
return 0;
/* Try to unplug any big blocks. */
virtio_mem_bbm_for_each_bb_rev(vm, bb_id, VIRTIO_MEM_BBM_BB_ADDED) {
cond_resched();
rc = virtio_mem_bbm_offline_remove_and_unplug_bb(vm, bb_id);
if (rc == -EBUSY)
continue;
if (!rc)
nb_bb--;
if (rc || !nb_bb)
return rc;
}
return nb_bb ? -EBUSY : 0;
}
/*
* Try to unplug the requested amount of memory.
*/
@ -1935,7 +2089,7 @@ static int virtio_mem_unplug_request(struct virtio_mem *vm, uint64_t diff)
{
if (vm->in_sbm)
return virtio_mem_sbm_unplug_request(vm, diff);
return -EBUSY;
return virtio_mem_bbm_unplug_request(vm, diff);
}
/*