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From: Konrad Rzeszutek Wilk on 6 Aug 2010 15:00
On Fri, Aug 06, 2010 at 01:11:47PM +0200, Daniel Kiper wrote:
> Hi,
>
> I am sending this e-mail once again because it probably
> has been lost in abyss of Xen-devel/LKLM list.
>
> Here is the second version of memory hotplug support
> for Xen guests patch. This one cleanly applies to
> git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git
> repository, xen/memory-hotplug head.
>
> Changes:
> - /sys/devices/system/memory/probe interface has been removed;
> /sys/devices/system/xen_memory/xen_memory0/{target,target_kb}
> are much better (I forgot about them),
> - most of the code have been moved to drivers/xen/balloon.c,
> - this changes forced me to export hotadd_new_pgdat and
> rollback_node_hotadd function from mm/memory_hotplug.c;
> could it be accepted by mm/memory_hotplug.c maintainers ???
> - PV on HVM mode is supported now; it was tested on
> git://xenbits.xen.org/people/sstabellini/linux-pvhvm.git
> repository, 2.6.34-pvhvm head,
> - most of Jeremy suggestions have been applied.
>
> On Wed, Jul 28, 2010 at 11:36:29AM +0400, Vasiliy G Tolstov wrote:
> [...]
> > Work's fine with opensuse 11.3 (dom0 and domU)
>
> Thx.
>
> On Thu, Jul 29, 2010 at 12:39:52PM -0700, Jeremy Fitzhardinge wrote:
> > On 07/26/2010 05:41 PM, Daniel Kiper wrote:
> > >Hi,
> > >
> > >Currently there is fully working version.
> > >It has been tested on Xen Ver. 4.0.0 in PV
> > >guest i386/x86_64 with Linux kernel Ver. 2.6.32.16
> > >and Ver. 2.6.34.1. This patch cleanly applys
> > >to Ver. 2.6.34.1
> >
> > Thanks. I've pushed this into xen.git as xen/memory-hotplug so people
> > can play with it more easily (but I haven't merged it into any of the
> > other branches yet).
>
> Thx.
>
> > >+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> > >+static inline unsigned long current_target(void)
> > >+{
> > >+ return balloon_stats.target_pages;
> >
> > Why does this need its own version?
>
> Because original version return values not bigger
> then initial memory allocation which does not allow
> memory hotplug to function.
>
> > >+int __ref xen_add_memory(int nid, u64 start, u64 size)
> > >+{
> > >+ pg_data_t *pgdat = NULL;
> > >+ int new_pgdat = 0, ret;
> > >+
> > >+ lock_system_sleep();
> > >+
> > >+ if (!node_online(nid)) {
> > >+ pgdat = hotadd_new_pgdat(nid, start);
> > >+ ret = -ENOMEM;
> > >+ if (!pgdat)
> > >+ goto out;
> > >+ new_pgdat = 1;
> > >+ }
> > >+
> > >+ /* call arch's memory hotadd */
> > >+ ret = arch_add_memory(nid, start, size);
> > >+
> > >+ if (ret< 0)
> > >+ goto error;
> > >+
> > >+ /* we online node here. we can't roll back from here. */
> > >+ node_set_online(nid);
> > >+
> > >+ if (new_pgdat) {
> > >+ ret = register_one_node(nid);
> > >+ /*
> > >+ * If sysfs file of new node can't create, cpu on the node
> > >+ * can't be hot-added. There is no rollback way now.
> > >+ * So, check by BUG_ON() to catch it reluctantly..
> > >+ */
> > >+ BUG_ON(ret);
> > >+ }
> >
> > This doesn't seem to be doing anything particularly xen-specific.
>
> In general it could be generic however I do not know
> it will be useful for others. If this function would
> be accepted by mm/memory_hotplug.c maintainers we could
> move it there. I removed from original add_memory funtion
> resource allocation (and deallocation after error), which
> must be done before XENMEM_populate_physmap in Xen. xen_add_memory
> is called after physmap is fully populated.
>
> If you have a questions please drop me a line.



Can you repost a patch that is on top of a virgin tree please?


>
> Daniel
>
> Signed-off-by: Daniel Kiper <dkiper(a)net-space.pl>
> ---
> arch/x86/Kconfig | 2 +-
> drivers/base/memory.c | 23 ---
> drivers/xen/Kconfig | 2 +-
> drivers/xen/balloon.c | 416 ++++++++++++++++++++++------------------
> include/linux/memory_hotplug.h | 10 +-
> include/xen/balloon.h | 6 -
> mm/Kconfig | 9 -
> mm/memory_hotplug.c | 146 +--------------
> 8 files changed, 240 insertions(+), 374 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 38434da..beb1aa7 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1273,7 +1273,7 @@ config ARCH_SELECT_MEMORY_MODEL
> depends on ARCH_SPARSEMEM_ENABLE
>
> config ARCH_MEMORY_PROBE
> - def_bool y
> + def_bool X86_64 && !XEN


Why?
> depends on MEMORY_HOTPLUG
>
> config ILLEGAL_POINTER_VALUE
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index 709457b..933442f 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -27,14 +27,6 @@
> #include <asm/atomic.h>
> #include <asm/uaccess.h>
>
> -#ifdef CONFIG_XEN_MEMORY_HOTPLUG
> -#include <xen/xen.h>
> -#endif
> -
> -#if defined(CONFIG_XEN_MEMORY_HOTPLUG) && defined(CONFIG_XEN_BALLOON)
> -#include <xen/balloon.h>
> -#endif
> -
> #define MEMORY_CLASS_NAME "memory"
>
> static struct sysdev_class memory_sysdev_class = {
> @@ -223,10 +215,6 @@ memory_block_action(struct memory_block *mem, unsigned long action)
> case MEM_ONLINE:
> start_pfn = page_to_pfn(first_page);
> ret = online_pages(start_pfn, PAGES_PER_SECTION);
> -#if defined(CONFIG_XEN_MEMORY_HOTPLUG) && defined(CONFIG_XEN_BALLOON)
> - if (xen_domain() && !ret)
> - balloon_update_stats(PAGES_PER_SECTION);
> -#endif
> break;
> case MEM_OFFLINE:
> mem->state = MEM_GOING_OFFLINE;
> @@ -237,10 +225,6 @@ memory_block_action(struct memory_block *mem, unsigned long action)
> mem->state = old_state;
> break;
> }
> -#if defined(CONFIG_XEN_MEMORY_HOTPLUG) && defined(CONFIG_XEN_BALLOON)
> - if (xen_domain())
> - balloon_update_stats(-PAGES_PER_SECTION);
> -#endif
> break;
> default:
> WARN(1, KERN_WARNING "%s(%p, %ld) unknown action: %ld\n",
> @@ -357,13 +341,6 @@ memory_probe_store(struct class *class, struct class_attribute *attr,
>
> phys_addr = simple_strtoull(buf, NULL, 0);
>
> -#ifdef CONFIG_XEN_MEMORY_HOTPLUG
> - if (xen_domain()) {
> - ret = xen_memory_probe(phys_addr);
> - return ret ? ret : count;
> - }
> -#endif
> -
> nid = memory_add_physaddr_to_nid(phys_addr);
> ret = add_memory(nid, phys_addr, PAGES_PER_SECTION << PAGE_SHIFT);
>
> diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
> index 9713048..4f35eaf 100644
> --- a/drivers/xen/Kconfig
> +++ b/drivers/xen/Kconfig
> @@ -11,8 +11,8 @@ config XEN_BALLOON
>
> config XEN_BALLOON_MEMORY_HOTPLUG
> bool "Xen memory balloon driver with memory hotplug support"
> - depends on EXPERIMENTAL && XEN_BALLOON && MEMORY_HOTPLUG
> default n
> + depends on XEN_BALLOON && MEMORY_HOTPLUG
> help
> Xen memory balloon driver with memory hotplug support allows expanding
> memory available for the system above limit declared at system startup.
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index f80bba0..31edc26 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -45,6 +45,8 @@
> #include <linux/list.h>
> #include <linux/sysdev.h>
> #include <linux/gfp.h>
> +#include <linux/memory.h>
> +#include <linux/suspend.h>
>
> #include <asm/page.h>
> #include <asm/pgalloc.h>
> @@ -62,10 +64,6 @@
> #include <xen/features.h>
> #include <xen/page.h>
>
> -#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> -#include <linux/memory.h>
> -#endif
> -
> #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
>
> #define BALLOON_CLASS_NAME "xen_memory"
> @@ -199,6 +197,196 @@ static inline unsigned long current_target(void)
> {
> return balloon_stats.target_pages;
> }
> +
> +static inline u64 is_memory_resource_reserved(void)
> +{
> + return balloon_stats.hotplug_start_paddr;
> +}
> +
> +/* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
> +static int __ref xen_add_memory(int nid, u64 start, u64 size)
> +{
> + pg_data_t *pgdat = NULL;
> + int new_pgdat = 0, ret;
> +
> + lock_system_sleep();
> +
> + if (!node_online(nid)) {
> + pgdat = hotadd_new_pgdat(nid, start);
> + ret = -ENOMEM;
> + if (!pgdat)
> + goto out;
> + new_pgdat = 1;
> + }
> +
> + /* call arch's memory hotadd */
> + ret = arch_add_memory(nid, start, size);
> +
> + if (ret < 0)
> + goto error;
> +
> + /* we online node here. we can't roll back from here. */
> + node_set_online(nid);
> +
> + if (new_pgdat) {
> + ret = register_one_node(nid);
> + /*
> + * If sysfs file of new node can't create, cpu on the node
> + * can't be hot-added. There is no rollback way now.
> + * So, check by BUG_ON() to catch it reluctantly..
> + */
> + BUG_ON(ret);
> + }
> +
> + goto out;
> +
> +error:
> + /* rollback pgdat allocation */
> + if (new_pgdat)
> + rollback_node_hotadd(nid, pgdat);
> +
> +out:
> + unlock_system_sleep();
> + return ret;
> +}
> +
> +static int allocate_additional_memory(unsigned long nr_pages)
> +{
> + long rc;
> + resource_size_t r_min, r_size;
> + struct resource *r;
> + struct xen_memory_reservation reservation = {
> + .address_bits = 0,
> + .extent_order = 0,
> + .domid = DOMID_SELF
> + };
> + unsigned long flags, i, pfn;
> +
> + if (nr_pages > ARRAY_SIZE(frame_list))
> + nr_pages = ARRAY_SIZE(frame_list);
> +
> + spin_lock_irqsave(&balloon_lock, flags);
> +
> + if (!is_memory_resource_reserved()) {
> +
> + /*
> + * Look for first unused memory region starting at page
> + * boundary. Skip last memory section created at boot time
> + * becuase it may contains unused memory pages with PG_reserved
> + * bit not set (online_pages require PG_reserved bit set).
> + */
> +
> + r = kzalloc(sizeof(struct resource), GFP_KERNEL);



You are holding a spinlock here. Kzalloc can sleep
> +
> + if (!r) {
> + rc = -ENOMEM;
> + goto out;
> + }
> +
> + r->name = "System RAM";
> + r->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
> + r_min = PFN_PHYS(section_nr_to_pfn(pfn_to_section_nr(balloon_stats.boot_max_pfn) + 1));
> + r_size = (balloon_stats.target_pages - balloon_stats.current_pages) << PAGE_SHIFT;
> +
> + rc = allocate_resource(&iomem_resource, r, r_size, r_min,
> + ULONG_MAX, PAGE_SIZE, NULL, NULL);



Ditto here. This can sleep and with a spinlock in place.
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From: Konrad Rzeszutek Wilk on 6 Aug 2010 17:20
> >Can you repost a patch that is on top of a virgin tree please?
>
> I just thanked him for posting a delta ;) I've pushed this into
> xen/memory-hotplug so you can easily generate a complete diff with
> "git diff v2.6.34..xen/memory-hotplug".

Ahh, I didn't know you had it in your tree already. Will use the git
diff for a more careful analysis.
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