MIPS: KVM: Add count frequency KVM register

Expose the KVM guest CP0_Count frequency to userland via a new
KVM_REG_MIPS_COUNT_HZ register accessible with the KVM_{GET,SET}_ONE_REG
ioctls.

When the frequency is altered the bias is adjusted such that the guest
CP0_Count doesn't jump discontinuously or lose any timer interrupts.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: kvm@vger.kernel.org
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: David Daney <david.daney@cavium.com>
Cc: Sanjay Lal <sanjayl@kymasys.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/mips/kvm/kvm_mips.c b/arch/mips/kvm/kvm_mips.c
index a2d5d4243f51..7ccb7a532c55 100644
--- a/arch/mips/kvm/kvm_mips.c
+++ b/arch/mips/kvm/kvm_mips.c
@@ -546,6 +546,7 @@ static u64 kvm_mips_get_one_regs[] = {
 
         KVM_REG_MIPS_COUNT_CTL,
         KVM_REG_MIPS_COUNT_RESUME,
+        KVM_REG_MIPS_COUNT_HZ,
 };
 
 static int kvm_mips_get_reg(struct kvm_vcpu *vcpu,
@@ -627,6 +628,7 @@ static int kvm_mips_get_reg(struct kvm_vcpu *vcpu,
         case KVM_REG_MIPS_CP0_COUNT:
         case KVM_REG_MIPS_COUNT_CTL:
         case KVM_REG_MIPS_COUNT_RESUME:
+        case KVM_REG_MIPS_COUNT_HZ:
                 ret = kvm_mips_callbacks->get_one_reg(vcpu, reg, &v);
                 if (ret)
                         return ret;
@@ -724,6 +726,7 @@ static int kvm_mips_set_reg(struct kvm_vcpu *vcpu,
         case KVM_REG_MIPS_CP0_CAUSE:
         case KVM_REG_MIPS_COUNT_CTL:
         case KVM_REG_MIPS_COUNT_RESUME:
+        case KVM_REG_MIPS_COUNT_HZ:
                 return kvm_mips_callbacks->set_one_reg(vcpu, reg, v);
         default:
                 return -EINVAL;