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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>
This commit is contained in:
Christian Borntraeger 2013-03-25 17:22:48 +01:00 committed by Gleb Natapov
parent 9a6d77d553
commit 2cef4deb40
1 changed files with 10 additions and 0 deletions
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10
arch/s390/kvm/kvm-s390.c
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@ -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);