MIPS: KVM: Wire up MSA capability

Now that the code is in place for KVM to support MIPS SIMD Architecutre
(MSA) in MIPS guests, wire up the new KVM_CAP_MIPS_MSA capability.

For backwards compatibility, the capability must be explicitly enabled
in order to detect or make use of MSA from the guest.

The capability is not supported if the hardware supports MSA vector
partitioning, since the extra support cannot be tested yet and it
extends the state that the userland program would have to save.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Cc: linux-api@vger.kernel.org
Cc: linux-doc@vger.kernel.org

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 35d3146895f1..bb68e8d520e8 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -880,6 +880,9 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
         case KVM_CAP_MIPS_FPU:
                 vcpu->arch.fpu_enabled = true;
                 break;
+        case KVM_CAP_MIPS_MSA:
+                vcpu->arch.msa_enabled = true;
+                break;
         default:
                 r = -EINVAL;
                 break;
@@ -1071,6 +1074,21 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
         case KVM_CAP_MIPS_FPU:
                 r = !!cpu_has_fpu;
                 break;
+        case KVM_CAP_MIPS_MSA:
+                /*
+                 * We don't support MSA vector partitioning yet:
+                 * 1) It would require explicit support which can't be tested
+                 *    yet due to lack of support in current hardware.
+                 * 2) It extends the state that would need to be saved/restored
+                 *    by e.g. QEMU for migration.
+                 *
+                 * When vector partitioning hardware becomes available, support
+                 * could be added by requiring a flag when enabling
+                 * KVM_CAP_MIPS_MSA capability to indicate that userland knows
+                 * to save/restore the appropriate extra state.
+                 */
+                r = cpu_has_msa && !(boot_cpu_data.msa_id & MSA_IR_WRPF);
+                break;
         default:
                 r = 0;
                 break;