From 2cef4deb4018c02fb3cd08f76c8a988f7ddee480 Mon Sep 17 00:00:00 2001 From: Christian Borntraeger Date: Mon, 25 Mar 2013 17:22:48 +0100 Subject: [PATCH] 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 Signed-off-by: Cornelia Huck Signed-off-by: Gleb Natapov --- 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); -- 2.7.4