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author | Paul Mackerras <paulus@ozlabs.org> | 2020-05-28 10:56:42 +1000 |
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committer | Paul Mackerras <paulus@ozlabs.org> | 2020-05-28 10:56:42 +1000 |
commit | 11362b1befeadaae4d159a8cddcdaf6b8afe08f9 (patch) | |
tree | 31e28225720a47331b4f3544cbc110fe29a448bd | |
parent | 3d89c2ef24f0772b7806ed289bef482b24083de6 (diff) | |
download | linux-stable-11362b1befeadaae4d159a8cddcdaf6b8afe08f9.tar.gz linux-stable-11362b1befeadaae4d159a8cddcdaf6b8afe08f9.tar.bz2 linux-stable-11362b1befeadaae4d159a8cddcdaf6b8afe08f9.zip |
KVM: PPC: Book3S HV: Close race with page faults around memslot flushes
There is a potential race condition between hypervisor page faults
and flushing a memslot. It is possible for a page fault to read the
memslot before a memslot is updated and then write a PTE to the
partition-scoped page tables after kvmppc_radix_flush_memslot has
completed. (Note that this race has never been explicitly observed.)
To close this race, it is sufficient to increment the MMU sequence
number while the kvm->mmu_lock is held. That will cause
mmu_notifier_retry() to return true, and the page fault will then
return to the guest without inserting a PTE.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
-rw-r--r-- | arch/powerpc/kvm/book3s_64_mmu_radix.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c index bc3f795252fd..aa41183d2a97 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c @@ -1130,6 +1130,11 @@ void kvmppc_radix_flush_memslot(struct kvm *kvm, kvm->arch.lpid); gpa += PAGE_SIZE; } + /* + * Increase the mmu notifier sequence number to prevent any page + * fault that read the memslot earlier from writing a PTE. + */ + kvm->mmu_notifier_seq++; spin_unlock(&kvm->mmu_lock); } |