From: Christian Borntraeger <borntraeger@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
---
arch/s390/kvm/kvm-s390.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 33161b4..f241e33 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);
--
1.7.12.4
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
