[Xen-devel] [PATCH 2/2] xen: before ballooning hotplugged memory, set frames to invalid

[Juergen Gross <jgross@xxxxxxxx>]

Commit 25b884a83d487fd62c3de7ac1ab5549979188482 ("x86/xen: set
regions above the end of RAM as 1:1") introduced a regression.

To be able to add memory pages which were added via memory hotplug to
a pv domain, the pages must be "invalid" instead of "identity" in the
p2m list before they can be added.

Suggested-by: David Vrabel <david.vrabel@xxxxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 drivers/xen/balloon.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 0b52d92..52e331f 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -221,15 +221,24 @@ static bool balloon_is_inflated(void)
 
 static enum bp_state reserve_additional_memory(long credit)
 {
-       int nid, rc;
+       int nid, rc = 0;
        u64 hotplug_start_paddr;
        unsigned long balloon_hotplug = credit;
+       unsigned long pfn;
 
        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);
 
-       rc = add_memory(nid, hotplug_start_paddr, balloon_hotplug << 
PAGE_SHIFT);
+       for (pfn = PFN_DOWN(hotplug_start_paddr);
+            !rc && pfn < PFN_DOWN(hotplug_start_paddr) + balloon_hotplug;
+            pfn++)
+               if (!set_phys_to_machine(pfn, INVALID_P2M_ENTRY))
+                       rc = 1;
+
+       if (!rc)
+               rc = add_memory(nid, hotplug_start_paddr,
+                               balloon_hotplug << PAGE_SHIFT);
 
        if (rc) {
                pr_warn("Cannot add additional memory (%i)\n", rc);
-- 
2.1.4


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