linux-kernel - [Patch V2 1/2] xen: prepare p2m list for memory hotplug

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Message-Id: <1426856139-3359-2-git-send-email-jgross@suse.com>
Date:	Fri, 20 Mar 2015 13:55:38 +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,
	pebolle@...cali.nl
Cc:	Juergen Gross <jgross@...e.com>
Subject: [Patch V2 1/2] xen: prepare p2m list for memory hotplug

Commit 054954eb051f35e74b75a566a96fe756015352c8 ("xen: switch to linear
virtual mapped sparse p2m list") introduced a regression regarding to
memory hotplug for a pv-domain: as the virtual space for the p2m list
is allocated for the to be expected memory size of the domain only,
hotplugged memory above that size will not be usable by the domain.

Correct this by using a configurable size for the p2m list in case of
memory hotplug enabled (default supported memory size is 512 GB for
64 bit domains and 4 GB for 32 bit domains).

Signed-off-by: Juergen Gross <jgross@...e.com>
---
 arch/x86/xen/p2m.c  | 10 +++++++++-
 drivers/xen/Kconfig | 14 ++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 9f93af5..b47124d 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -91,6 +91,12 @@ EXPORT_SYMBOL_GPL(xen_p2m_size);
 unsigned long xen_max_p2m_pfn __read_mostly;
 EXPORT_SYMBOL_GPL(xen_max_p2m_pfn);
 
+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
+#define P2M_LIMIT CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
+#else
+#define P2M_LIMIT 0
+#endif
+
 static DEFINE_SPINLOCK(p2m_update_lock);
 
 static unsigned long *p2m_mid_missing_mfn;
@@ -385,9 +391,11 @@ static void __init xen_rebuild_p2m_list(unsigned long *p2m)
 void __init xen_vmalloc_p2m_tree(void)
 {
 	static struct vm_struct vm;
+	unsigned long p2m_limit;
 
+	p2m_limit = (phys_addr_t)P2M_LIMIT * 1024 * 1024 * 1024 / PAGE_SIZE;
 	vm.flags = VM_ALLOC;
-	vm.size = ALIGN(sizeof(unsigned long) * xen_max_p2m_pfn,
+	vm.size = ALIGN(sizeof(unsigned long) * max(xen_max_p2m_pfn, p2m_limit),
 			PMD_SIZE * PMDS_PER_MID_PAGE);
 	vm_area_register_early(&vm, PMD_SIZE * PMDS_PER_MID_PAGE);
 	pr_notice("p2m virtual area at %p, size is %lx\n", vm.addr, vm.size);
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index b812462..0f1b509 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -55,6 +55,20 @@ config XEN_BALLOON_MEMORY_HOTPLUG
 
 	  In that case step 3 should be omitted.
 
+config XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
+	int
+	default 512 if X86_64
+	default 4 if X86_32
+	range 0 64 if X86_32
+	depends on XEN_HAVE_PVMMU
+	depends on XEN_BALLOON_MEMORY_HOTPLUG
+	help
+	  Upper limit in GBs a pv domain can be expanded to using memory
+	  hotplug.
+
+	  This value is used to allocate enough space in internal tables needed
+	  for physical memory administration.
+
 config XEN_SCRUB_PAGES
 	bool "Scrub pages before returning them to system"
 	depends on XEN_BALLOON
-- 
2.1.4

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