Re: [Xen-devel] [PATCH RFC 7/8] mm: allow to control onlining/offlining of memory by a driver

2018-04-13 Thread David Hildenbrand 
On 13.04.2018 17:59, Michal Hocko wrote:
> On Fri 13-04-18 15:33:28, David Hildenbrand wrote:
>> Some devices (esp. paravirtualized) might want to control
>> - when to online/offline a memory block
>> - how to online memory (MOVABLE/NORMAL)
>> - in which granularity to online/offline memory
>>
>> So let's add a new flag "driver_managed" and disallow to change the
>> state by user space. Device onlining/offlining will still work, however
>> the memory will not be actually onlined/offlined. That has to be handled
>> by the device driver that owns the memory.
> 
> Is there any reason to create the memblock sysfs interface to this
> memory at all? ZONE_DEVICE mem hotplug users currently do not do that
> and manage the memory themselves. It seems you want to achieve the same
> thing, no?
> 

Yes, I think so, namely kdump. We have to retrigger kexec() whenever a
memory block is added/removed. udev events are sent for that reason when
a memory block is created/deleted. And I think this is not done for
ZONE_DEVICE devices, or am I wrong?

-- 

Thanks,

David / dhildenb

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Re: [Xen-devel] [PATCH RFC 7/8] mm: allow to control onlining/offlining of memory by a driver

2018-04-13 Thread Michal Hocko 
On Fri 13-04-18 15:33:28, David Hildenbrand wrote:
> Some devices (esp. paravirtualized) might want to control
> - when to online/offline a memory block
> - how to online memory (MOVABLE/NORMAL)
> - in which granularity to online/offline memory
> 
> So let's add a new flag "driver_managed" and disallow to change the
> state by user space. Device onlining/offlining will still work, however
> the memory will not be actually onlined/offlined. That has to be handled
> by the device driver that owns the memory.

Is there any reason to create the memblock sysfs interface to this
memory at all? ZONE_DEVICE mem hotplug users currently do not do that
and manage the memory themselves. It seems you want to achieve the same
thing, no?
-- 
Michal Hocko
SUSE Labs

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[Xen-devel] [PATCH RFC 7/8] mm: allow to control onlining/offlining of memory by a driver

2018-04-13 Thread David Hildenbrand 
Some devices (esp. paravirtualized) might want to control
- when to online/offline a memory block
- how to online memory (MOVABLE/NORMAL)
- in which granularity to online/offline memory

So let's add a new flag "driver_managed" and disallow to change the
state by user space. Device onlining/offlining will still work, however
the memory will not be actually onlined/offlined. That has to be handled
by the device driver that owns the memory.

Signed-off-by: David Hildenbrand 
---
 drivers/base/memory.c  | 22 ++
 drivers/xen/balloon.c  |  2 +-
 include/linux/memory.h |  1 +
 include/linux/memory_hotplug.h |  4 +++-
 mm/memory_hotplug.c| 34 --
 5 files changed, 51 insertions(+), 12 deletions(-)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index bffe8616bd55..3b8616551561 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -231,27 +231,28 @@ static bool pages_correctly_probed(unsigned long 
start_pfn)
  * Must already be protected by mem_hotplug_begin().
  */
 static int
-memory_block_action(unsigned long phys_index, unsigned long action, int 
online_type)
+memory_block_action(struct memory_block *mem, unsigned long action)
 {
-   unsigned long start_pfn;
+   unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);
unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
-   int ret;
+   int ret = 0;
 
-   start_pfn = section_nr_to_pfn(phys_index);
+   if (mem->driver_managed)
+   return 0;
 
switch (action) {
case MEM_ONLINE:
if (!pages_correctly_probed(start_pfn))
return -EBUSY;
 
-   ret = online_pages(start_pfn, nr_pages, online_type);
+   ret = online_pages(start_pfn, nr_pages, mem->online_type);
break;
case MEM_OFFLINE:
ret = offline_pages(start_pfn, nr_pages);
break;
default:
WARN(1, KERN_WARNING "%s(%ld, %ld) unknown action: "
-"%ld\n", __func__, phys_index, action, action);
+"%ld\n", __func__, mem->start_section_nr, action, action);
ret = -EINVAL;
}
 
@@ -269,8 +270,7 @@ static int memory_block_change_state(struct memory_block 
*mem,
if (to_state == MEM_OFFLINE)
mem->state = MEM_GOING_OFFLINE;
 
-   ret = memory_block_action(mem->start_section_nr, to_state,
-   mem->online_type);
+   ret = memory_block_action(mem, to_state);
 
mem->state = ret ? from_state_req : to_state;
 
@@ -350,6 +350,11 @@ store_mem_state(struct device *dev,
 */
mem_hotplug_begin();
 
+   if (mem->driver_managed) {
+   ret = -EINVAL;
+   goto out;
+   }
+
switch (online_type) {
case MMOP_ONLINE_KERNEL:
case MMOP_ONLINE_MOVABLE:
@@ -364,6 +369,7 @@ store_mem_state(struct device *dev,
ret = -EINVAL; /* should never happen */
}
 
+out:
mem_hotplug_done();
 err:
unlock_device_hotplug();
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 065f0b607373..89981d573c06 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -401,7 +401,7 @@ static enum bp_state reserve_additional_memory(void)
 * callers drop the mutex before trying again.
 */
mutex_unlock(_mutex);
-   rc = add_memory_resource(nid, resource, memhp_auto_online);
+   rc = add_memory_resource(nid, resource, memhp_auto_online, false);
mutex_lock(_mutex);
 
if (rc) {
diff --git a/include/linux/memory.h b/include/linux/memory.h
index 9f8cd856ca1e..018c5e5ecde1 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -29,6 +29,7 @@ struct memory_block {
unsigned long state;/* serialized by the dev->lock */
int section_count;  /* serialized by mem_sysfs_mutex */
int online_type;/* for passing data to online routine */
+   bool driver_managed;/* driver handles online/offline */
int phys_device;/* to which fru does this belong? */
void *hw;   /* optional pointer to fw/hw data */
int (*phys_callback)(struct memory_block *);
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index e0e49b5b1ee1..46c6ceb1110d 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -320,7 +320,9 @@ static inline void remove_memory(int nid, u64 start, u64 
size) {}
 extern int walk_memory_range(unsigned long start_pfn, unsigned long end_pfn,
void *arg, int (*func)(struct memory_block *, void *));
 extern int add_memory(int nid, u64 start, u64 size);
-extern int add_memory_resource(int nid, struct resource *resource, bool