On Tue, May 11, 2021, Ben Gardon wrote:
> Add a new lock to protect the arch-specific fields of memslots if they
> need to be modified in a kvm->srcu read critical section. A future
> commit will use this lock to lazily allocate memslot rmaps for x86.
>
> Signed-off-by: Ben Gardon <bgardon@xxxxxxxxxx>
> ---
> include/linux/kvm_host.h | 9 +++++++++
> virt/kvm/kvm_main.c | 31 ++++++++++++++++++++++++++-----
> 2 files changed, 35 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 8895b95b6a22..2d5e797fbb08 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -472,6 +472,15 @@ struct kvm {
> #endif /* KVM_HAVE_MMU_RWLOCK */
>
> struct mutex slots_lock;
> +
> + /*
> + * Protects the arch-specific fields of struct kvm_memory_slots in
> + * use by the VM. To be used under the slots_lock (above) or in a
> + * kvm->srcu read cirtical section where acquiring the slots_lock
^^^^^^^^
critical
> + * would lead to deadlock with the synchronize_srcu in
> + * install_new_memslots.
> + */
> + struct mutex slots_arch_lock;
> struct mm_struct *mm; /* userspace tied to this vm */
> struct kvm_memslots __rcu *memslots[KVM_ADDRESS_SPACE_NUM];
> struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
