[PATCHv3 00/10] mm, xen/balloon: memory hotplug improvements

[PATCHv3 00/10] mm, xen/balloon: memory hotplug improvements

[David Vrabel]

The series improves the use of hotplug memory in the Xen balloon
driver.

- Reliably find a non-conflicting location for the hotplugged memory
  (this fixes memory hotplug in a number of cases, particularly in
  dom0).

- Use hotplugged memory for alloc_xenballooned_pages() (keeping more
  memory available for the domain and reducing fragmentation of the
  p2m).

Changes in v3:
- xen.balloon.hotplug_unpopulated sysctl to enable using hotplug to
  provide unpopulated (ballooned) pages.
- Fix xen_alloc_p2m_entry() for auto-translated guests.

Changes in v2:
- New BP_WAIT state to signal the balloon process to wait for
  userspace to online the new memory.
- Preallocate P2M entries in alloc_xenballooned_pages() so they do not
  need allocated later (in a context where GFP_KERNEL allocations are
  not possible).

David

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[PATCHv3 01/10] mm: memory hotplug with an existing resource

[David Vrabel]

Add add_memory_resource() to add memory using an existing "System RAM"
resource.  This is useful if the memory region is being located by
finding a free resource slot with allocate_resource().

Xen guests will make use of this in their balloon driver to hotplug
arbitrary amounts of memory in response to toolstack requests.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
 include/linux/memory_hotplug.h |  2 ++
 mm/memory_hotplug.c            | 28 +++++++++++++++++++++-------
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 6ffa0ac..c76d371 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -11,6 +11,7 @@ struct zone;
 struct pglist_data;
 struct mem_section;
 struct memory_block;
+struct resource;
 
 #ifdef CONFIG_MEMORY_HOTPLUG
 
@@ -266,6 +267,7 @@ 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);
 extern int zone_for_memory(int nid, u64 start, u64 size, int zone_default);
 extern int arch_add_memory(int nid, u64 start, u64 size);
 extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 003dbe4..169770a 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1224,23 +1224,21 @@ int zone_for_memory(int nid, u64 start, u64 size, int zone_default)
 }
 
 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
-int __ref add_memory(int nid, u64 start, u64 size)
+int __ref add_memory_resource(int nid, struct resource *res)
 {
+	u64 start, size;
 	pg_data_t *pgdat = NULL;
 	bool new_pgdat;
 	bool new_node;
-	struct resource *res;
 	int ret;
 
+	start = res->start;
+	size = resource_size(res);
+
 	ret = check_hotplug_memory_range(start, size);
 	if (ret)
 		return ret;
 
-	res = register_memory_resource(start, size);
-	ret = -EEXIST;
-	if (!res)
-		return ret;
-
 	{	/* Stupid hack to suppress address-never-null warning */
 		void *p = NODE_DATA(nid);
 		new_pgdat = !p;
@@ -1290,6 +1288,22 @@ out:
 	mem_hotplug_done();
 	return ret;
 }
+EXPORT_SYMBOL_GPL(add_memory_resource);
+
+int __ref add_memory(int nid, u64 start, u64 size)
+{
+	struct resource *res;
+	int ret;
+
+	res = register_memory_resource(start, size);
+	if (!res)
+		return -EEXIST;
+
+	ret = add_memory_resource(nid, res);
+	if (ret < 0)
+		release_memory_resource(res);
+	return ret;
+}
 EXPORT_SYMBOL_GPL(add_memory);
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
-- 
2.1.4

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Re: [PATCHv3 01/10] mm: memory hotplug with an existing resource

[Daniel Kiper]

On Thu, Jul 30, 2015 at 06:03:03PM +0100, David Vrabel wrote:
> Add add_memory_resource() to add memory using an existing "System RAM"
> resource.  This is useful if the memory region is being located by
> finding a free resource slot with allocate_resource().
>
> Xen guests will make use of this in their balloon driver to hotplug
> arbitrary amounts of memory in response to toolstack requests.
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>

Hmmm... Why do you remove my Reviewed-by line from this patch?

Daniel

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Re: [Xen-devel] [PATCHv3 01/10] mm: memory hotplug with an existing resource

[David Vrabel]

On 30/07/15 18:03, David Vrabel wrote:
> Add add_memory_resource() to add memory using an existing "System RAM"
> resource.  This is useful if the memory region is being located by
> finding a free resource slot with allocate_resource().
> 
> Xen guests will make use of this in their balloon driver to hotplug
> arbitrary amounts of memory in response to toolstack requests.

Ping?  This enables a useful feature for Xen guests.

> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> ---
>  include/linux/memory_hotplug.h |  2 ++
>  mm/memory_hotplug.c            | 28 +++++++++++++++++++++-------
>  2 files changed, 23 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 6ffa0ac..c76d371 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -11,6 +11,7 @@ struct zone;
>  struct pglist_data;
>  struct mem_section;
>  struct memory_block;
> +struct resource;
>  
>  #ifdef CONFIG_MEMORY_HOTPLUG
>  
> @@ -266,6 +267,7 @@ 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);
>  extern int zone_for_memory(int nid, u64 start, u64 size, int zone_default);
>  extern int arch_add_memory(int nid, u64 start, u64 size);
>  extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 003dbe4..169770a 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1224,23 +1224,21 @@ int zone_for_memory(int nid, u64 start, u64 size, int zone_default)
>  }
>  
>  /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
> -int __ref add_memory(int nid, u64 start, u64 size)
> +int __ref add_memory_resource(int nid, struct resource *res)
>  {
> +	u64 start, size;
>  	pg_data_t *pgdat = NULL;
>  	bool new_pgdat;
>  	bool new_node;
> -	struct resource *res;
>  	int ret;
>  
> +	start = res->start;
> +	size = resource_size(res);
> +
>  	ret = check_hotplug_memory_range(start, size);
>  	if (ret)
>  		return ret;
>  
> -	res = register_memory_resource(start, size);
> -	ret = -EEXIST;
> -	if (!res)
> -		return ret;
> -
>  	{	/* Stupid hack to suppress address-never-null warning */
>  		void *p = NODE_DATA(nid);
>  		new_pgdat = !p;
> @@ -1290,6 +1288,22 @@ out:
>  	mem_hotplug_done();
>  	return ret;
>  }
> +EXPORT_SYMBOL_GPL(add_memory_resource);
> +
> +int __ref add_memory(int nid, u64 start, u64 size)
> +{
> +	struct resource *res;
> +	int ret;
> +
> +	res = register_memory_resource(start, size);
> +	if (!res)
> +		return -EEXIST;
> +
> +	ret = add_memory_resource(nid, res);
> +	if (ret < 0)
> +		release_memory_resource(res);
> +	return ret;
> +}
>  EXPORT_SYMBOL_GPL(add_memory);
>  
>  #ifdef CONFIG_MEMORY_HOTREMOVE
> 

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Re: [Xen-devel] [PATCHv3 01/10] mm: memory hotplug with an existing resource

[Andrew Morton]

On Thu, 13 Aug 2015 11:21:43 +0100 David Vrabel <david.vrabel@citrix.com> wrote:

> On 30/07/15 18:03, David Vrabel wrote:
> > Add add_memory_resource() to add memory using an existing "System RAM"
> > resource.  This is useful if the memory region is being located by
> > finding a free resource slot with allocate_resource().
> > 
> > Xen guests will make use of this in their balloon driver to hotplug
> > arbitrary amounts of memory in response to toolstack requests.
> 
> Ping?  This enables a useful feature for Xen guests.
> 

Looks OK to me.  I've cc'ed some memory_hotplug.c developers.  If
they're OK with it, please add the patch to the (Xen?) tree which uses
it.




Add add_memory_resource() to add memory using an existing "System RAM"
resource.  This is useful if the memory region is being located by
finding a free resource slot with allocate_resource().

Xen guests will make use of this in their balloon driver to hotplug
arbitrary amounts of memory in response to toolstack requests.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
 include/linux/memory_hotplug.h |  2 ++
 mm/memory_hotplug.c            | 28 +++++++++++++++++++++-------
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 6ffa0ac..c76d371 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -11,6 +11,7 @@ struct zone;
 struct pglist_data;
 struct mem_section;
 struct memory_block;
+struct resource;
 
 #ifdef CONFIG_MEMORY_HOTPLUG
 
@@ -266,6 +267,7 @@ 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);
 extern int zone_for_memory(int nid, u64 start, u64 size, int zone_default);
 extern int arch_add_memory(int nid, u64 start, u64 size);
 extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 003dbe4..169770a 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1224,23 +1224,21 @@ int zone_for_memory(int nid, u64 start, u64 size, int zone_default)
 }
 
 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
-int __ref add_memory(int nid, u64 start, u64 size)
+int __ref add_memory_resource(int nid, struct resource *res)
 {
+	u64 start, size;
 	pg_data_t *pgdat = NULL;
 	bool new_pgdat;
 	bool new_node;
-	struct resource *res;
 	int ret;
 
+	start = res->start;
+	size = resource_size(res);
+
 	ret = check_hotplug_memory_range(start, size);
 	if (ret)
 		return ret;
 
-	res = register_memory_resource(start, size);
-	ret = -EEXIST;
-	if (!res)
-		return ret;
-
 	{	/* Stupid hack to suppress address-never-null warning */
 		void *p = NODE_DATA(nid);
 		new_pgdat = !p;
@@ -1290,6 +1288,22 @@ out:
 	mem_hotplug_done();
 	return ret;
 }
+EXPORT_SYMBOL_GPL(add_memory_resource);
+
+int __ref add_memory(int nid, u64 start, u64 size)
+{
+	struct resource *res;
+	int ret;
+
+	res = register_memory_resource(start, size);
+	if (!res)
+		return -EEXIST;
+
+	ret = add_memory_resource(nid, res);
+	if (ret < 0)
+		release_memory_resource(res);
+	return ret;
+}
 EXPORT_SYMBOL_GPL(add_memory);
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
-- 
2.1.4

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Re: [Xen-devel] [PATCHv3 01/10] mm: memory hotplug with an existing resource

[Tang Chen]

On 08/14/2015 04:40 AM, Andrew Morton wrote:
> On Thu, 13 Aug 2015 11:21:43 +0100 David Vrabel <david.vrabel@citrix.com> wrote:
>
>> On 30/07/15 18:03, David Vrabel wrote:
>>> Add add_memory_resource() to add memory using an existing "System RAM"
>>> resource.  This is useful if the memory region is being located by
>>> finding a free resource slot with allocate_resource().
>>>
>>> Xen guests will make use of this in their balloon driver to hotplug
>>> arbitrary amounts of memory in response to toolstack requests.
>> Ping?  This enables a useful feature for Xen guests.
>>
> Looks OK to me.  I've cc'ed some memory_hotplug.c developers.  If
> they're OK with it, please add the patch to the (Xen?) tree which uses
> it.
>
>
>
>
> Add add_memory_resource() to add memory using an existing "System RAM"
> resource.  This is useful if the memory region is being located by
> finding a free resource slot with allocate_resource().
>
> Xen guests will make use of this in their balloon driver to hotplug
> arbitrary amounts of memory in response to toolstack requests.
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> ---
>   include/linux/memory_hotplug.h |  2 ++
>   mm/memory_hotplug.c            | 28 +++++++++++++++++++++-------
>   2 files changed, 23 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 6ffa0ac..c76d371 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -11,6 +11,7 @@ struct zone;
>   struct pglist_data;
>   struct mem_section;
>   struct memory_block;
> +struct resource;
>   
>   #ifdef CONFIG_MEMORY_HOTPLUG
>   
> @@ -266,6 +267,7 @@ 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);
>   extern int zone_for_memory(int nid, u64 start, u64 size, int zone_default);
>   extern int arch_add_memory(int nid, u64 start, u64 size);
>   extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 003dbe4..169770a 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1224,23 +1224,21 @@ int zone_for_memory(int nid, u64 start, u64 size, int zone_default)
>   }
>   
>   /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
> -int __ref add_memory(int nid, u64 start, u64 size)
> +int __ref add_memory_resource(int nid, struct resource *res)
>   {
> +	u64 start, size;
>   	pg_data_t *pgdat = NULL;
>   	bool new_pgdat;
>   	bool new_node;
> -	struct resource *res;
>   	int ret;
>   
> +	start = res->start;
> +	size = resource_size(res);
> +
>   	ret = check_hotplug_memory_range(start, size);
>   	if (ret)
>   		return ret;
>   
> -	res = register_memory_resource(start, size);
> -	ret = -EEXIST;
> -	if (!res)
> -		return ret;
> -
>   	{	/* Stupid hack to suppress address-never-null warning */
>   		void *p = NODE_DATA(nid);
>   		new_pgdat = !p;
> @@ -1290,6 +1288,22 @@ out:
>   	mem_hotplug_done();
>   	return ret;
>   }
> +EXPORT_SYMBOL_GPL(add_memory_resource);
> +
> +int __ref add_memory(int nid, u64 start, u64 size)
> +{
> +	struct resource *res;
> +	int ret;
> +
> +	res = register_memory_resource(start, size);
> +	if (!res)
> +		return -EEXIST;
> +
> +	ret = add_memory_resource(nid, res);
> +	if (ret < 0)

Not a big deal, but I think  "if (ret)"  is enough.

The code looks good.

Reviewed-by: Tang Chen <tangchen@cn.fujitsu.com>

Thanks.

> +		release_memory_resource(res);
> +	return ret;
> +}
>   EXPORT_SYMBOL_GPL(add_memory);
>   
>   #ifdef CONFIG_MEMORY_HOTREMOVE

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[PATCHv3 02/10] xen/balloon: remove scratch page left overs

[David Vrabel]

Commit 0bb599fd30108883b00c7d4a226eeb49111e6932 (xen: remove scratch
frames for ballooned pages and m2p override) removed the use of the
scratch page for ballooned out pages.

Remove some left over function definitions.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 include/xen/balloon.h | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/include/xen/balloon.h b/include/xen/balloon.h
index a4c1c6a..cc2e1a7 100644
--- a/include/xen/balloon.h
+++ b/include/xen/balloon.h
@@ -29,9 +29,6 @@ int alloc_xenballooned_pages(int nr_pages, struct page **pages,
 		bool highmem);
 void free_xenballooned_pages(int nr_pages, struct page **pages);
 
-struct page *get_balloon_scratch_page(void);
-void put_balloon_scratch_page(void);
-
 struct device;
 #ifdef CONFIG_XEN_SELFBALLOONING
 extern int register_xen_selfballooning(struct device *dev);
-- 
2.1.4

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[PATCHv3 03/10] x86/xen: discard RAM regions above the maximum reservation

[David Vrabel]

During setup, discard RAM regions that are above the maximum
reservation (instead of marking them as E820_UNUSABLE).  This allows
hotplug memory to be placed at these addresses.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 arch/x86/xen/setup.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 55f388e..32910c5 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -646,6 +646,7 @@ char * __init xen_memory_setup(void)
 		phys_addr_t addr = map[i].addr;
 		phys_addr_t size = map[i].size;
 		u32 type = map[i].type;
+		bool discard = false;
 
 		if (type == E820_RAM) {
 			if (addr < mem_end) {
@@ -656,10 +657,11 @@ char * __init xen_memory_setup(void)
 				xen_add_extra_mem(addr, size);
 				xen_max_p2m_pfn = PFN_DOWN(addr + size);
 			} else
-				type = E820_UNUSABLE;
+				discard = true;
 		}
 
-		xen_align_and_add_e820_region(addr, size, type);
+		if (!discard)
+			xen_align_and_add_e820_region(addr, size, type);
 
 		map[i].addr += size;
 		map[i].size -= size;
-- 
2.1.4

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[PATCHv3 04/10] xen/balloon: find non-conflicting regions to place hotplugged memory

[David Vrabel]

Instead of placing hotplugged memory at the end of RAM (which may
conflict with PCI devices or reserved regions) use allocate_resource()
to get a new, suitably aligned resource that does not conflict.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
v3:
- Remove stale comment.
---
 drivers/xen/balloon.c | 73 +++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 53 insertions(+), 20 deletions(-)

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index fd93369..7ecbbc5 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -54,6 +54,7 @@
 #include <linux/memory.h>
 #include <linux/memory_hotplug.h>
 #include <linux/percpu-defs.h>
+#include <linux/slab.h>
 
 #include <asm/page.h>
 #include <asm/pgalloc.h>
@@ -208,26 +209,56 @@ static bool balloon_is_inflated(void)
 		return false;
 }
 
-/*
- * reserve_additional_memory() adds memory region of size >= credit above
- * max_pfn. New region is section aligned and size is modified to be multiple
- * of section size. Those features allow optimal use of address space and
- * establish proper alignment when this function is called first time after
- * boot (last section not fully populated at boot time contains unused memory
- * pages with PG_reserved bit not set; online_pages_range() does not allow page
- * onlining in whole range if first onlined page does not have PG_reserved
- * bit set). Real size of added memory is established at page onlining stage.
- */
+static struct resource *additional_memory_resource(phys_addr_t size)
+{
+	struct resource *res;
+	int ret;
+
+	res = kzalloc(sizeof(*res), GFP_KERNEL);
+	if (!res)
+		return NULL;
+
+	res->name = "System RAM";
+	res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+
+	ret = allocate_resource(&iomem_resource, res,
+				size, 0, -1,
+				PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
+	if (ret < 0) {
+		pr_err("Cannot allocate new System RAM resource\n");
+		kfree(res);
+		return NULL;
+	}
+
+	return res;
+}
+
+static void release_memory_resource(struct resource *resource)
+{
+	if (!resource)
+		return;
+
+	/*
+	 * No need to reset region to identity mapped since we now
+	 * know that no I/O can be in this region
+	 */
+	release_resource(resource);
+	kfree(resource);
+}
 
 static enum bp_state reserve_additional_memory(long credit)
 {
+	struct resource *resource;
 	int nid, rc;
-	u64 hotplug_start_paddr;
-	unsigned long balloon_hotplug = credit;
+	unsigned long balloon_hotplug;
+
+	balloon_hotplug = round_up(credit, PAGES_PER_SECTION);
+
+	resource = additional_memory_resource(balloon_hotplug * PAGE_SIZE);
+	if (!resource)
+		goto err;
 
-	hotplug_start_paddr = PFN_PHYS(SECTION_ALIGN_UP(max_pfn));
-	balloon_hotplug = round_up(balloon_hotplug, PAGES_PER_SECTION);
-	nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
+	nid = memory_add_physaddr_to_nid(resource->start);
 
 #ifdef CONFIG_XEN_HAVE_PVMMU
         /*
@@ -242,21 +273,20 @@ static enum bp_state reserve_additional_memory(long credit)
 	if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 		unsigned long pfn, i;
 
-		pfn = PFN_DOWN(hotplug_start_paddr);
+		pfn = PFN_DOWN(resource->start);
 		for (i = 0; i < balloon_hotplug; i++) {
 			if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
 				pr_warn("set_phys_to_machine() failed, no memory added\n");
-				return BP_ECANCELED;
+				goto err;
 			}
                 }
 	}
 #endif
 
-	rc = add_memory(nid, hotplug_start_paddr, balloon_hotplug << PAGE_SHIFT);
-
+	rc = add_memory_resource(nid, resource);
 	if (rc) {
 		pr_warn("Cannot add additional memory (%i)\n", rc);
-		return BP_ECANCELED;
+		goto err;
 	}
 
 	balloon_hotplug -= credit;
@@ -265,6 +295,9 @@ static enum bp_state reserve_additional_memory(long credit)
 	balloon_stats.balloon_hotplug = balloon_hotplug;
 
 	return BP_DONE;
+  err:
+	release_memory_resource(resource);
+	return BP_ECANCELED;
 }
 
 static void xen_online_page(struct page *page)
-- 
2.1.4

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[PATCHv3 05/10] xen/balloon: rationalize memory hotplug stats

[David Vrabel]

The stats used for memory hotplug make no sense and are fiddled with
in odd ways.  Remove them and introduce total_pages to track the total
number of pages (both populated and unpopulated) including those within
hotplugged regions (note that this includes not yet onlined pages).

This will be used in a subsequent commit (xen/balloon: only hotplug
additional memory if required) when deciding whether additional memory
needs to be hotplugged.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 drivers/xen/balloon.c | 75 +++++++++------------------------------------------
 include/xen/balloon.h |  5 +---
 2 files changed, 13 insertions(+), 67 deletions(-)

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 7ecbbc5..932d232 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -194,21 +194,6 @@ static enum bp_state update_schedule(enum bp_state state)
 }
 
 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
-static long current_credit(void)
-{
-	return balloon_stats.target_pages - balloon_stats.current_pages -
-		balloon_stats.hotplug_pages;
-}
-
-static bool balloon_is_inflated(void)
-{
-	if (balloon_stats.balloon_low || balloon_stats.balloon_high ||
-			balloon_stats.balloon_hotplug)
-		return true;
-	else
-		return false;
-}
-
 static struct resource *additional_memory_resource(phys_addr_t size)
 {
 	struct resource *res;
@@ -289,10 +274,7 @@ static enum bp_state reserve_additional_memory(long credit)
 		goto err;
 	}
 
-	balloon_hotplug -= credit;
-
-	balloon_stats.hotplug_pages += credit;
-	balloon_stats.balloon_hotplug = balloon_hotplug;
+	balloon_stats.total_pages += balloon_hotplug;
 
 	return BP_DONE;
   err:
@@ -308,11 +290,6 @@ static void xen_online_page(struct page *page)
 
 	__balloon_append(page);
 
-	if (balloon_stats.hotplug_pages)
-		--balloon_stats.hotplug_pages;
-	else
-		--balloon_stats.balloon_hotplug;
-
 	mutex_unlock(&balloon_mutex);
 }
 
@@ -329,32 +306,22 @@ static struct notifier_block xen_memory_nb = {
 	.priority = 0
 };
 #else
-static long current_credit(void)
+static enum bp_state reserve_additional_memory(long credit)
 {
-	unsigned long target = balloon_stats.target_pages;
-
-	target = min(target,
-		     balloon_stats.current_pages +
-		     balloon_stats.balloon_low +
-		     balloon_stats.balloon_high);
-
-	return target - balloon_stats.current_pages;
+	balloon_stats.target_pages = balloon_stats.current_pages;
+	return BP_DONE;
 }
+#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
 
-static bool balloon_is_inflated(void)
+static long current_credit(void)
 {
-	if (balloon_stats.balloon_low || balloon_stats.balloon_high)
-		return true;
-	else
-		return false;
+	return balloon_stats.target_pages - balloon_stats.current_pages;
 }
 
-static enum bp_state reserve_additional_memory(long credit)
+static bool balloon_is_inflated(void)
 {
-	balloon_stats.target_pages = balloon_stats.current_pages;
-	return BP_DONE;
+	return balloon_stats.balloon_low || balloon_stats.balloon_high;
 }
-#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
 
 static enum bp_state increase_reservation(unsigned long nr_pages)
 {
@@ -367,15 +334,6 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
 		.domid        = DOMID_SELF
 	};
 
-#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
-	if (!balloon_stats.balloon_low && !balloon_stats.balloon_high) {
-		nr_pages = min(nr_pages, balloon_stats.balloon_hotplug);
-		balloon_stats.hotplug_pages += nr_pages;
-		balloon_stats.balloon_hotplug -= nr_pages;
-		return BP_DONE;
-	}
-#endif
-
 	if (nr_pages > ARRAY_SIZE(frame_list))
 		nr_pages = ARRAY_SIZE(frame_list);
 
@@ -438,15 +396,6 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
 		.domid        = DOMID_SELF
 	};
 
-#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
-	if (balloon_stats.hotplug_pages) {
-		nr_pages = min(nr_pages, balloon_stats.hotplug_pages);
-		balloon_stats.hotplug_pages -= nr_pages;
-		balloon_stats.balloon_hotplug += nr_pages;
-		return BP_DONE;
-	}
-#endif
-
 	if (nr_pages > ARRAY_SIZE(frame_list))
 		nr_pages = ARRAY_SIZE(frame_list);
 
@@ -636,6 +585,8 @@ static void __init balloon_add_region(unsigned long start_pfn,
 		   don't subtract from it. */
 		__balloon_append(page);
 	}
+
+	balloon_stats.total_pages += extra_pfn_end - start_pfn;
 }
 
 static int __init balloon_init(void)
@@ -653,6 +604,7 @@ static int __init balloon_init(void)
 	balloon_stats.target_pages  = balloon_stats.current_pages;
 	balloon_stats.balloon_low   = 0;
 	balloon_stats.balloon_high  = 0;
+	balloon_stats.total_pages   = balloon_stats.current_pages;
 
 	balloon_stats.schedule_delay = 1;
 	balloon_stats.max_schedule_delay = 32;
@@ -660,9 +612,6 @@ static int __init balloon_init(void)
 	balloon_stats.max_retry_count = RETRY_UNLIMITED;
 
 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
-	balloon_stats.hotplug_pages = 0;
-	balloon_stats.balloon_hotplug = 0;
-
 	set_online_page_callback(&xen_online_page);
 	register_memory_notifier(&xen_memory_nb);
 #endif
diff --git a/include/xen/balloon.h b/include/xen/balloon.h
index cc2e1a7..c8aee7a 100644
--- a/include/xen/balloon.h
+++ b/include/xen/balloon.h
@@ -11,14 +11,11 @@ struct balloon_stats {
 	/* Number of pages in high- and low-memory balloons. */
 	unsigned long balloon_low;
 	unsigned long balloon_high;
+	unsigned long total_pages;
 	unsigned long schedule_delay;
 	unsigned long max_schedule_delay;
 	unsigned long retry_count;
 	unsigned long max_retry_count;
-#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
-	unsigned long hotplug_pages;
-	unsigned long balloon_hotplug;
-#endif
 };
 
 extern struct balloon_stats balloon_stats;
-- 
2.1.4

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[PATCHv3 06/10] xen/balloon: only hotplug additional memory if required

[David Vrabel]

Now that we track the total number of pages (included hotplugged
regions), it is easy to determine if more memory needs to be
hotplugged.

Add a new BP_WAIT state to signal that the balloon process needs to
wait until kicked by the memory add notifier (when the new section is
onlined by userspace).

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
v3:
- Return BP_WAIT if enough sections are already hotplugged.

v2:
- New BP_WAIT status after adding new memory sections.
---
 drivers/xen/balloon.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 932d232..e8b45e8 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -75,12 +75,14 @@
  * balloon_process() state:
  *
  * BP_DONE: done or nothing to do,
+ * BP_WAIT: wait to be rescheduled,
  * BP_EAGAIN: error, go to sleep,
  * BP_ECANCELED: error, balloon operation canceled.
  */
 
 enum bp_state {
 	BP_DONE,
+	BP_WAIT,
 	BP_EAGAIN,
 	BP_ECANCELED
 };
@@ -167,6 +169,9 @@ static struct page *balloon_next_page(struct page *page)
 
 static enum bp_state update_schedule(enum bp_state state)
 {
+	if (state == BP_WAIT)
+		return BP_WAIT;
+
 	if (state == BP_ECANCELED)
 		return BP_ECANCELED;
 
@@ -231,12 +236,22 @@ static void release_memory_resource(struct resource *resource)
 	kfree(resource);
 }
 
-static enum bp_state reserve_additional_memory(long credit)
+static enum bp_state reserve_additional_memory(void)
 {
+	long credit;
 	struct resource *resource;
 	int nid, rc;
 	unsigned long balloon_hotplug;
 
+	credit = balloon_stats.target_pages - balloon_stats.total_pages;
+
+	/*
+	 * Already hotplugged enough pages?  Wait for them to be
+	 * onlined.
+	 */
+	if (credit <= 0)
+		return BP_WAIT;
+
 	balloon_hotplug = round_up(credit, PAGES_PER_SECTION);
 
 	resource = additional_memory_resource(balloon_hotplug * PAGE_SIZE);
@@ -276,7 +291,7 @@ static enum bp_state reserve_additional_memory(long credit)
 
 	balloon_stats.total_pages += balloon_hotplug;
 
-	return BP_DONE;
+	return BP_WAIT;
   err:
 	release_memory_resource(resource);
 	return BP_ECANCELED;
@@ -306,7 +321,7 @@ static struct notifier_block xen_memory_nb = {
 	.priority = 0
 };
 #else
-static enum bp_state reserve_additional_memory(long credit)
+static enum bp_state reserve_additional_memory(void)
 {
 	balloon_stats.target_pages = balloon_stats.current_pages;
 	return BP_DONE;
@@ -473,7 +488,7 @@ static void balloon_process(struct work_struct *work)
 			if (balloon_is_inflated())
 				state = increase_reservation(credit);
 			else
-				state = reserve_additional_memory(credit);
+				state = reserve_additional_memory();
 		}
 
 		if (credit < 0)
-- 
2.1.4

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Re: [PATCHv3 06/10] xen/balloon: only hotplug additional memory if required

[Daniel Kiper]

On Thu, Jul 30, 2015 at 06:03:08PM +0100, David Vrabel wrote:
> Now that we track the total number of pages (included hotplugged
> regions), it is easy to determine if more memory needs to be
> hotplugged.
>
> Add a new BP_WAIT state to signal that the balloon process needs to
> wait until kicked by the memory add notifier (when the new section is
> onlined by userspace).
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>

Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

Daniel

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[PATCHv3 07/10] xen/balloon: make alloc_xenballoon_pages() always allocate low pages

[David Vrabel]

All users of alloc_xenballoon_pages() wanted low memory pages, so
remove the option for high memory.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 arch/x86/xen/grant-table.c         |  2 +-
 drivers/xen/balloon.c              | 21 ++++++++-------------
 drivers/xen/grant-table.c          |  2 +-
 drivers/xen/privcmd.c              |  2 +-
 drivers/xen/xenbus/xenbus_client.c |  3 +--
 include/xen/balloon.h              |  3 +--
 6 files changed, 13 insertions(+), 20 deletions(-)

diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c
index 1580e7a..e079500 100644
--- a/arch/x86/xen/grant-table.c
+++ b/arch/x86/xen/grant-table.c
@@ -133,7 +133,7 @@ static int __init xlated_setup_gnttab_pages(void)
 		kfree(pages);
 		return -ENOMEM;
 	}
-	rc = alloc_xenballooned_pages(nr_grant_frames, pages, 0 /* lowmem */);
+	rc = alloc_xenballooned_pages(nr_grant_frames, pages);
 	if (rc) {
 		pr_warn("%s Couldn't balloon alloc %ld pfns rc:%d\n", __func__,
 			nr_grant_frames, rc);
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index e8b45e8..2a01da7 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -136,17 +136,16 @@ static void balloon_append(struct page *page)
 }
 
 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
-static struct page *balloon_retrieve(bool prefer_highmem)
+static struct page *balloon_retrieve(bool require_lowmem)
 {
 	struct page *page;
 
 	if (list_empty(&ballooned_pages))
 		return NULL;
 
-	if (prefer_highmem)
-		page = list_entry(ballooned_pages.prev, struct page, lru);
-	else
-		page = list_entry(ballooned_pages.next, struct page, lru);
+	page = list_entry(ballooned_pages.next, struct page, lru);
+	if (require_lowmem && PageHighMem(page))
+		return NULL;
 	list_del(&page->lru);
 
 	if (PageHighMem(page))
@@ -522,24 +521,20 @@ EXPORT_SYMBOL_GPL(balloon_set_new_target);
  * alloc_xenballooned_pages - get pages that have been ballooned out
  * @nr_pages: Number of pages to get
  * @pages: pages returned
- * @highmem: allow highmem pages
  * @return 0 on success, error otherwise
  */
-int alloc_xenballooned_pages(int nr_pages, struct page **pages, bool highmem)
+int alloc_xenballooned_pages(int nr_pages, struct page **pages)
 {
 	int pgno = 0;
 	struct page *page;
 	mutex_lock(&balloon_mutex);
 	while (pgno < nr_pages) {
-		page = balloon_retrieve(highmem);
-		if (page && (highmem || !PageHighMem(page))) {
+		page = balloon_retrieve(true);
+		if (page) {
 			pages[pgno++] = page;
 		} else {
 			enum bp_state st;
-			if (page)
-				balloon_append(page);
-			st = decrease_reservation(nr_pages - pgno,
-					highmem ? GFP_HIGHUSER : GFP_USER);
+			st = decrease_reservation(nr_pages - pgno, GFP_USER);
 			if (st != BP_DONE)
 				goto out_undo;
 		}
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 62f591f..a4b702c 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -687,7 +687,7 @@ int gnttab_alloc_pages(int nr_pages, struct page **pages)
 	int i;
 	int ret;
 
-	ret = alloc_xenballooned_pages(nr_pages, pages, false);
+	ret = alloc_xenballooned_pages(nr_pages, pages);
 	if (ret < 0)
 		return ret;
 
diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 5a29616..59cfec9 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -401,7 +401,7 @@ static int alloc_empty_pages(struct vm_area_struct *vma, int numpgs)
 	if (pages == NULL)
 		return -ENOMEM;
 
-	rc = alloc_xenballooned_pages(numpgs, pages, 0);
+	rc = alloc_xenballooned_pages(numpgs, pages);
 	if (rc != 0) {
 		pr_warn("%s Could not alloc %d pfns rc:%d\n", __func__,
 			numpgs, rc);
diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index 9ad3272..2a2da04 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -614,8 +614,7 @@ static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
 	if (!node)
 		return -ENOMEM;
 
-	err = alloc_xenballooned_pages(nr_grefs, node->hvm.pages,
-				       false /* lowmem */);
+	err = alloc_xenballooned_pages(nr_grefs, node->hvm.pages);
 	if (err)
 		goto out_err;
 
diff --git a/include/xen/balloon.h b/include/xen/balloon.h
index c8aee7a..83efdeb 100644
--- a/include/xen/balloon.h
+++ b/include/xen/balloon.h
@@ -22,8 +22,7 @@ extern struct balloon_stats balloon_stats;
 
 void balloon_set_new_target(unsigned long target);
 
-int alloc_xenballooned_pages(int nr_pages, struct page **pages,
-		bool highmem);
+int alloc_xenballooned_pages(int nr_pages, struct page **pages);
 void free_xenballooned_pages(int nr_pages, struct page **pages);
 
 struct device;
-- 
2.1.4

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[PATCHv3 08/10] xen/balloon: use hotplugged pages for foreign mappings etc.

[David Vrabel]

alloc_xenballooned_pages() is used to get ballooned pages to back
foreign mappings etc.  Instead of having to balloon out real pages,
use (if supported) hotplugged memory.

This makes more memory available to the guest and reduces
fragmentation in the p2m.

This is only enabled if the xen.balloon.hotplug_unpopulated sysctl is
set to 1.  This sysctl defaults to 0 in case the udev rules to
automatically online hotplugged memory do not exist.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
v3:
- Add xen.balloon.hotplug_unpopulated sysctl to enable use of hotplug
  for unpopulated pages.
---
 drivers/xen/balloon.c | 87 +++++++++++++++++++++++++++++++++++++++++++++------
 include/xen/balloon.h |  1 +
 2 files changed, 79 insertions(+), 9 deletions(-)

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 2a01da7..3094f38f 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -55,6 +55,7 @@
 #include <linux/memory_hotplug.h>
 #include <linux/percpu-defs.h>
 #include <linux/slab.h>
+#include <linux/sysctl.h>
 
 #include <asm/page.h>
 #include <asm/pgalloc.h>
@@ -71,6 +72,46 @@
 #include <xen/features.h>
 #include <xen/page.h>
 
+static int xen_hotplug_unpopulated;
+
+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
+
+static int zero;
+static int one = 1;
+
+static struct ctl_table balloon_table[] = {
+	{
+		.procname	= "hotplug_unpopulated",
+		.data		= &xen_hotplug_unpopulated,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1         = &zero,
+		.extra2         = &one,
+	},
+	{ }
+};
+
+static struct ctl_table balloon_root[] = {
+	{
+		.procname	= "balloon",
+		.mode		= 0555,
+		.child		= balloon_table,
+	},
+	{ }
+};
+
+static struct ctl_table xen_root[] = {
+	{
+		.procname	= "xen",
+		.mode		= 0555,
+		.child		= balloon_root,
+	},
+	{ }
+};
+
+#endif
+
 /*
  * balloon_process() state:
  *
@@ -99,6 +140,7 @@ static xen_pfn_t frame_list[PAGE_SIZE / sizeof(unsigned long)];
 
 /* List of ballooned pages, threaded through the mem_map array. */
 static LIST_HEAD(ballooned_pages);
+static DECLARE_WAIT_QUEUE_HEAD(balloon_wq);
 
 /* Main work function, always executed in process context. */
 static void balloon_process(struct work_struct *work);
@@ -127,6 +169,7 @@ static void __balloon_append(struct page *page)
 		list_add(&page->lru, &ballooned_pages);
 		balloon_stats.balloon_low++;
 	}
+	wake_up(&balloon_wq);
 }
 
 static void balloon_append(struct page *page)
@@ -242,7 +285,8 @@ static enum bp_state reserve_additional_memory(void)
 	int nid, rc;
 	unsigned long balloon_hotplug;
 
-	credit = balloon_stats.target_pages - balloon_stats.total_pages;
+	credit = balloon_stats.target_pages + balloon_stats.target_unpopulated
+		- balloon_stats.total_pages;
 
 	/*
 	 * Already hotplugged enough pages?  Wait for them to be
@@ -323,7 +367,7 @@ static struct notifier_block xen_memory_nb = {
 static enum bp_state reserve_additional_memory(void)
 {
 	balloon_stats.target_pages = balloon_stats.current_pages;
-	return BP_DONE;
+	return BP_ECANCELED;
 }
 #endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
 
@@ -517,6 +561,28 @@ void balloon_set_new_target(unsigned long target)
 }
 EXPORT_SYMBOL_GPL(balloon_set_new_target);
 
+static int add_ballooned_pages(int nr_pages)
+{
+	enum bp_state st;
+
+	if (xen_hotplug_unpopulated) {
+		st = reserve_additional_memory();
+		if (st != BP_ECANCELED) {
+			mutex_unlock(&balloon_mutex);
+			wait_event(balloon_wq,
+				   !list_empty(&ballooned_pages));
+			mutex_lock(&balloon_mutex);
+			return 0;
+		}
+	}
+
+	st = decrease_reservation(nr_pages, GFP_USER);
+	if (st != BP_DONE)
+		return -ENOMEM;
+
+	return 0;
+}
+
 /**
  * alloc_xenballooned_pages - get pages that have been ballooned out
  * @nr_pages: Number of pages to get
@@ -527,26 +593,26 @@ int alloc_xenballooned_pages(int nr_pages, struct page **pages)
 {
 	int pgno = 0;
 	struct page *page;
+
 	mutex_lock(&balloon_mutex);
+
+	balloon_stats.target_unpopulated += nr_pages;
+
 	while (pgno < nr_pages) {
 		page = balloon_retrieve(true);
 		if (page) {
 			pages[pgno++] = page;
 		} else {
-			enum bp_state st;
-			st = decrease_reservation(nr_pages - pgno, GFP_USER);
-			if (st != BP_DONE)
+			ret = add_ballooned_pages(nr_pages - pgno);
+			if (ret < 0)
 				goto out_undo;
 		}
 	}
 	mutex_unlock(&balloon_mutex);
 	return 0;
  out_undo:
-	while (pgno)
-		balloon_append(pages[--pgno]);
-	/* Free the memory back to the kernel soon */
-	schedule_delayed_work(&balloon_worker, 0);
 	mutex_unlock(&balloon_mutex);
+	free_xenballooned_pages(pgno, pages);
 	return -ENOMEM;
 }
 EXPORT_SYMBOL(alloc_xenballooned_pages);
@@ -567,6 +633,8 @@ void free_xenballooned_pages(int nr_pages, struct page **pages)
 			balloon_append(pages[i]);
 	}
 
+	balloon_stats.target_unpopulated -= nr_pages;
+
 	/* The balloon may be too large now. Shrink it if needed. */
 	if (current_credit())
 		schedule_delayed_work(&balloon_worker, 0);
@@ -624,6 +692,7 @@ static int __init balloon_init(void)
 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 	set_online_page_callback(&xen_online_page);
 	register_memory_notifier(&xen_memory_nb);
+	register_sysctl_table(xen_root);
 #endif
 
 	/*
diff --git a/include/xen/balloon.h b/include/xen/balloon.h
index 83efdeb..d1767df 100644
--- a/include/xen/balloon.h
+++ b/include/xen/balloon.h
@@ -8,6 +8,7 @@ struct balloon_stats {
 	/* We aim for 'current allocation' == 'target allocation'. */
 	unsigned long current_pages;
 	unsigned long target_pages;
+	unsigned long target_unpopulated;
 	/* Number of pages in high- and low-memory balloons. */
 	unsigned long balloon_low;
 	unsigned long balloon_high;
-- 
2.1.4

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Re: [PATCHv3 08/10] xen/balloon: use hotplugged pages for foreign mappings etc.

[Daniel Kiper]

On Thu, Jul 30, 2015 at 06:03:10PM +0100, David Vrabel wrote:
> alloc_xenballooned_pages() is used to get ballooned pages to back
> foreign mappings etc.  Instead of having to balloon out real pages,
> use (if supported) hotplugged memory.
>
> This makes more memory available to the guest and reduces
> fragmentation in the p2m.
>
> This is only enabled if the xen.balloon.hotplug_unpopulated sysctl is
> set to 1.  This sysctl defaults to 0 in case the udev rules to
> automatically online hotplugged memory do not exist.
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>

Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

Daniel

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[PATCHv3 09/10] x86/xen: export xen_alloc_p2m_entry()

[David Vrabel]

Rename alloc_p2m() to xen_alloc_p2m_entry() and export it.

This is useful for ensuring that a p2m entry is allocated (i.e., not a
shared missing or identity entry) so that subsequent set_phys_to_machine()
calls will require no further allocations.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
v3:
- Make xen_alloc_p2m_entry() a nop on auto-xlate guests.
---
 arch/x86/include/asm/xen/page.h |  2 ++
 arch/x86/xen/p2m.c              | 19 +++++++++++++------
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index c44a5d5..960b380 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -45,6 +45,8 @@ extern unsigned long *xen_p2m_addr;
 extern unsigned long  xen_p2m_size;
 extern unsigned long  xen_max_p2m_pfn;
 
+extern int xen_alloc_p2m_entry(unsigned long pfn);
+
 extern unsigned long get_phys_to_machine(unsigned long pfn);
 extern bool set_phys_to_machine(unsigned long pfn, unsigned long mfn);
 extern bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn);
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 8b7f18e..0215897 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -503,7 +503,7 @@ static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *pte_pg)
  * the new pages are installed with cmpxchg; if we lose the race then
  * simply free the page we allocated and use the one that's there.
  */
-static bool alloc_p2m(unsigned long pfn)
+int xen_alloc_p2m_entry(unsigned long pfn)
 {
 	unsigned topidx, mididx;
 	unsigned long *top_mfn_p, *mid_mfn;
@@ -513,6 +513,9 @@ static bool alloc_p2m(unsigned long pfn)
 	unsigned long addr = (unsigned long)(xen_p2m_addr + pfn);
 	unsigned long p2m_pfn;
 
+	if (xen_feature(XENFEAT_auto_translated_physmap))
+		return 0;
+
 	topidx = p2m_top_index(pfn);
 	mididx = p2m_mid_index(pfn);
 
@@ -524,7 +527,7 @@ static bool alloc_p2m(unsigned long pfn)
 		/* PMD level is missing, allocate a new one */
 		ptep = alloc_p2m_pmd(addr, pte_pg);
 		if (!ptep)
-			return false;
+			return -ENOMEM;
 	}
 
 	if (p2m_top_mfn) {
@@ -541,7 +544,7 @@ static bool alloc_p2m(unsigned long pfn)
 
 			mid_mfn = alloc_p2m_page();
 			if (!mid_mfn)
-				return false;
+				return -ENOMEM;
 
 			p2m_mid_mfn_init(mid_mfn, p2m_missing);
 
@@ -567,7 +570,7 @@ static bool alloc_p2m(unsigned long pfn)
 
 		p2m = alloc_p2m_page();
 		if (!p2m)
-			return false;
+			return -ENOMEM;
 
 		if (p2m_pfn == PFN_DOWN(__pa(p2m_missing)))
 			p2m_init(p2m);
@@ -590,8 +593,9 @@ static bool alloc_p2m(unsigned long pfn)
 			free_p2m_page(p2m);
 	}
 
-	return true;
+	return 0;
 }
+EXPORT_SYMBOL(xen_alloc_p2m_entry);
 
 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
 				      unsigned long pfn_e)
@@ -648,7 +652,10 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 {
 	if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
-		if (!alloc_p2m(pfn))
+		int ret;
+
+		ret = xen_alloc_p2m_entry(pfn);
+		if (ret < 0)
 			return false;
 
 		return __set_phys_to_machine(pfn, mfn);
-- 
2.1.4

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Re: [PATCHv3 09/10] x86/xen: export xen_alloc_p2m_entry()

[Daniel Kiper]

On Thu, Jul 30, 2015 at 06:03:11PM +0100, David Vrabel wrote:
> Rename alloc_p2m() to xen_alloc_p2m_entry() and export it.
>
> This is useful for ensuring that a p2m entry is allocated (i.e., not a
> shared missing or identity entry) so that subsequent set_phys_to_machine()
> calls will require no further allocations.
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>

Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

Daniel

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[PATCHv3 10/10] xen/balloon: pre-allocate p2m entries for ballooned pages

[David Vrabel]

Pages returned by alloc_xenballooned_pages() will be used for grant
mapping which will call set_phys_to_machine() (in PV guests).

Ballooned pages are set as INVALID_P2M_ENTRY in the p2m and thus may
be using the (shared) missing tables and a subsequent
set_phys_to_machine() will need to allocate new tables.

Since the grant mapping may be done from a context that cannot sleep,
the p2m entries must already be allocated.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 drivers/xen/balloon.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 3094f38f..e040cf4 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -593,6 +593,7 @@ int alloc_xenballooned_pages(int nr_pages, struct page **pages)
 {
 	int pgno = 0;
 	struct page *page;
+	int ret = -ENOMEM;
 
 	mutex_lock(&balloon_mutex);
 
@@ -602,6 +603,11 @@ int alloc_xenballooned_pages(int nr_pages, struct page **pages)
 		page = balloon_retrieve(true);
 		if (page) {
 			pages[pgno++] = page;
+#ifdef CONFIG_XEN_HAVE_PVMMU
+			ret = xen_alloc_p2m_entry(page_to_pfn(page));
+			if (ret < 0)
+				goto out_undo;
+#endif
 		} else {
 			ret = add_ballooned_pages(nr_pages - pgno);
 			if (ret < 0)
@@ -613,7 +619,7 @@ int alloc_xenballooned_pages(int nr_pages, struct page **pages)
  out_undo:
 	mutex_unlock(&balloon_mutex);
 	free_xenballooned_pages(pgno, pages);
-	return -ENOMEM;
+	return ret;
 }
 EXPORT_SYMBOL(alloc_xenballooned_pages);
 
-- 
2.1.4

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Re: [PATCHv3 10/10] xen/balloon: pre-allocate p2m entries for ballooned pages

[Daniel Kiper]

On Thu, Jul 30, 2015 at 06:03:12PM +0100, David Vrabel wrote:
> Pages returned by alloc_xenballooned_pages() will be used for grant
> mapping which will call set_phys_to_machine() (in PV guests).
>
> Ballooned pages are set as INVALID_P2M_ENTRY in the p2m and thus may
> be using the (shared) missing tables and a subsequent
> set_phys_to_machine() will need to allocate new tables.
>
> Since the grant mapping may be done from a context that cannot sleep,
> the p2m entries must already be allocated.
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>

Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

Daniel

PS FYI, next week I am on vacation.

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Re: [Xen-devel] [PATCHv3 00/10] mm, xen/balloon: memory hotplug improvements

[David Vrabel]

On 30/07/15 18:03, David Vrabel wrote:
> The series improves the use of hotplug memory in the Xen balloon
> driver.
> 
> - Reliably find a non-conflicting location for the hotplugged memory
>   (this fixes memory hotplug in a number of cases, particularly in
>   dom0).
> 
> - Use hotplugged memory for alloc_xenballooned_pages() (keeping more
>   memory available for the domain and reducing fragmentation of the
>   p2m).

Applied to for-linus-4.4.

David

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