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author | Marc Zyngier <maz@kernel.org> | 2022-09-26 15:51:15 +0100 |
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committer | Marc Zyngier <maz@kernel.org> | 2022-09-29 10:23:08 +0100 |
commit | 8929bc9659640f35dd2ef8373263cbd885b4a072 (patch) | |
tree | 387c5d5d8eea6e87da003f2757aa93b9ff09ae67 /arch/x86/kvm | |
parent | b90cb1053190353cc30f0fef0ef1f378ccc063c5 (diff) | |
download | linux-8929bc9659640f35dd2ef8373263cbd885b4a072.tar.bz2 |
KVM: Use acquire/release semantics when accessing dirty ring GFN state
The current implementation of the dirty ring has an implicit requirement
that stores to the dirty ring from userspace must be:
- be ordered with one another
- visible from another CPU executing a ring reset
While these implicit requirements work well for x86 (and any other
TSO-like architecture), they do not work for more relaxed architectures
such as arm64 where stores to different addresses can be freely
reordered, and loads from these addresses not observing writes from
another CPU unless the required barriers (or acquire/release semantics)
are used.
In order to start fixing this, upgrade the ring reset accesses:
- the kvm_dirty_gfn_harvested() helper now uses acquire semantics
so it is ordered after all previous writes, including that from
userspace
- the kvm_dirty_gfn_set_invalid() helper now uses release semantics
so that the next_slot and next_offset reads don't drift past
the entry invalidation
This is only a partial fix as the userspace side also need upgrading.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/20220926145120.27974-2-maz@kernel.org
Diffstat (limited to 'arch/x86/kvm')
0 files changed, 0 insertions, 0 deletions