From: Dominik Dingel <dingel@linux.vnet.ibm.com>
Date: Mon, 24 Mar 2014 13:27:58 +0000 (+0100)
Subject: KVM: s390/mm: new gmap_test_and_clear_dirty function
X-Git-Tag: v3.16-rc4~21^2^2~35^2~48
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=a0bf4f149bbfa2e31b5f4172c817afdb7b986733;p=linux.git

KVM: s390/mm: new gmap_test_and_clear_dirty function

For live migration kvm needs to test and clear the dirty bit of guest pages.

That for is ptep_test_and_clear_user_dirty, to be sure we are not racing with
other code, we protect the pte. This needs to be done within
the architecture memory management code.

Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index b2c630df0ca5..fcba5e03839f 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -838,6 +838,8 @@ unsigned long __gmap_fault(unsigned long address, struct gmap *);
 unsigned long gmap_fault(unsigned long address, struct gmap *);
 void gmap_discard(unsigned long from, unsigned long to, struct gmap *);
 void __gmap_zap(unsigned long address, struct gmap *);
+bool gmap_test_and_clear_dirty(unsigned long address, struct gmap *);
+
 
 void gmap_register_ipte_notifier(struct gmap_notifier *);
 void gmap_unregister_ipte_notifier(struct gmap_notifier *);
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 1ddf975352a0..ea4a31b95990 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -1401,6 +1401,27 @@ void s390_enable_skey(void)
 }
 EXPORT_SYMBOL_GPL(s390_enable_skey);
 
+/*
+ * Test and reset if a guest page is dirty
+ */
+bool gmap_test_and_clear_dirty(unsigned long address, struct gmap *gmap)
+{
+	pte_t *pte;
+	spinlock_t *ptl;
+	bool dirty = false;
+
+	pte = get_locked_pte(gmap->mm, address, &ptl);
+	if (unlikely(!pte))
+		return false;
+
+	if (ptep_test_and_clear_user_dirty(gmap->mm, address, pte))
+		dirty = true;
+
+	spin_unlock(ptl);
+	return dirty;
+}
+EXPORT_SYMBOL_GPL(gmap_test_and_clear_dirty);
+
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 int pmdp_clear_flush_young(struct vm_area_struct *vma, unsigned long address,
 			   pmd_t *pmdp)