• Paul Mackerras's avatar
    KVM: PPC: Book3S: Use new mutex to synchronize access to rtas token list · 9b3bd09b
    Paul Mackerras authored
    [ Upstream commit 1659e27d ]
    
    Currently the Book 3S KVM code uses kvm->lock to synchronize access
    to the kvm->arch.rtas_tokens list.  Because this list is scanned
    inside kvmppc_rtas_hcall(), which is called with the vcpu mutex held,
    taking kvm->lock cause a lock inversion problem, which could lead to
    a deadlock.
    
    To fix this, we add a new mutex, kvm->arch.rtas_token_lock, which nests
    inside the vcpu mutexes, and use that instead of kvm->lock when
    accessing the rtas token list.
    
    This removes the lockdep_assert_held() in kvmppc_rtas_tokens_free().
    At this point we don't hold the new mutex, but that is OK because
    kvmppc_rtas_tokens_free() is only called when the whole VM is being
    destroyed, and at that point nothing can be looking up a token in
    the list.
    Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
    Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
    9b3bd09b
book3s.c 27.3 KB