[PATCH 2/2] RISC-V: KVM: Disallow GPA-width changes after AIA init

[Pengpeng Hou]

KVM_ENABLE_CAP(KVM_CAP_VM_GPA_BITS) allows userspace to reduce the
stage-2 GPA width while a VM has no vCPUs or memory slots.

AIA initialization can still complete with an APLIC and no vCPUs or
memory slots.  In that state, the APLIC MMIO device has already been
registered, but the existing checks allow userspace to shrink the GPA
width below its address.

Reject GPA-width changes after AIA initialization.  Both paths hold
kvm->lock, so the check also closes the race between final AIA address
validation and publication.

Fixes: 7263b4fdb0b2 ("RISC-V: KVM: Reuse KVM_CAP_VM_GPA_BITS to select HGATP.MODE")
Signed-off-by: Pengpeng Hou <pengpeng at iscas.ac.cn>
---
 arch/riscv/kvm/vm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c
index a9f083feeb76..66edfaa86243 100644
--- a/arch/riscv/kvm/vm.c
+++ b/arch/riscv/kvm/vm.c
@@ -250,7 +250,8 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
 		mutex_lock(&kvm->lock);
 		mutex_lock(&kvm->slots_lock);
 
-		if (kvm->created_vcpus || !kvm_are_all_memslots_empty(kvm))
+		if (kvm->created_vcpus || !kvm_are_all_memslots_empty(kvm) ||
+		    kvm_riscv_aia_initialized(kvm))
 			r = -EBUSY;
 		else
 			kvm->arch.pgd_levels = new_levels;
-- 
2.50.1 (Apple Git-155)