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KVM: s390/interrupt: do not pin adapter interrupt pages

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The adapter interrupt page containing the indicator bits is currently
pinned. That means that a guest with many devices can pin a lot of
memory pages in the host. This also complicates the reference tracking
which is needed for memory management handling of protected virtual
machines. It might also have some strange side effects for madvise
MADV_DONTNEED and other things.

We can simply try to get the userspace page set the bits and free the
page. By storing the userspace address in the irq routing entry instead
of the guest address we can actually avoid many lookups and list walks
so that this variant is very likely not slower.

If userspace messes around with the memory slots the worst thing that
can happen is that we write to some other memory within that process.
As we get the the page with FOLL_WRITE this can also not be used to
write to shared read-only pages.

Signed-off-by: Ulrich Weigand <Ulrich.Weigand@de.ibm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
[borntraeger@de.ibm.com: patch simplification]
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
This commit is contained in:
Ulrich Weigand
2020-02-04 08:51:58 -05:00
committed by Christian Borntraeger
parent f15587c834
commit f65470661f
3 changed files with 51 additions and 133 deletions
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11
Documentation/virt/kvm/devices/s390_flic.rst
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@@ -108,16 +108,9 @@ Groups:
mask or unmask the adapter, as specified in mask
KVM_S390_IO_ADAPTER_MAP
perform a gmap translation for the guest address provided in addr,
pin a userspace page for the translated address and add it to the
list of mappings
.. note:: A new mapping will be created unconditionally; therefore,
the calling code should avoid making duplicate mappings.
This is now a no-op. The mapping is purely done by the irq route.
KVM_S390_IO_ADAPTER_UNMAP
release a userspace page for the translated address specified in addr
from the list of mappings
This is now a no-op. The mapping is purely done by the irq route.
KVM_DEV_FLIC_AISM
modify the adapter-interruption-suppression mode for a given isc if the