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

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Date:	Thu, 19 Mar 2015 15:31:02 +0100
From:	Juergen Gross <jgross@...e.com>
To:	linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
	konrad.wilk@...cle.com, david.vrabel@...rix.com,
	boris.ostrovsky@...cle.com, daniel.kiper@...cle.com
Cc:	Juergen Gross <jgross@...e.com>
Subject: [PATCH 2/2] xen: before ballooning hotplugged memory, set frames to invalid

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@...rix.com>
Signed-off-by: Juergen Gross <jgross@...e.com>
---
 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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