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authorChristian Borntraeger <borntraeger@de.ibm.com>2013-03-25 17:22:48 +0100
committerGleb Natapov <gleb@redhat.com>2013-04-02 16:14:07 +0300
commit2cef4deb4018c02fb3cd08f76c8a988f7ddee480 (patch)
tree8a97a4fa75b0b1c03afdb55b213e72b402e90673
parent9a6d77d553856f461cdb5b6969b48da3a2b1f8e9 (diff)
KVM: s390: Dont do a gmap update on minor memslot changes
Some memslot updates dont affect the gmap implementation, e.g. setting/unsetting dirty tracking. Since a gmap update will cause tlb flushes and segment table invalidations we want to avoid that. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
-rw-r--r--arch/s390/kvm/kvm-s390.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 33161b4a8280..f241e3315ebb 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1007,6 +1007,16 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
{
int rc;
+ /* If the basics of the memslot do not change, we do not want
+ * to update the gmap. Every update causes several unnecessary
+ * segment translation exceptions. This is usually handled just
+ * fine by the normal fault handler + gmap, but it will also
+ * cause faults on the prefix page of running guest CPUs.
+ */
+ if (old->userspace_addr == mem->userspace_addr &&
+ old->base_gfn * PAGE_SIZE == mem->guest_phys_addr &&
+ old->npages * PAGE_SIZE == mem->memory_size)
+ return;
rc = gmap_map_segment(kvm->arch.gmap, mem->userspace_addr,
mem->guest_phys_addr, mem->memory_size);