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

[David Vrabel <david.vrabel@xxxxxxxxxx>]

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