KVM: X86: Implement userspace interface to set virtual_tsc_khz

This patch implements two new vm-ioctls to get and set the
virtual_tsc_khz if the machine supports tsc-scaling. Setting
the tsc-frequency is only possible before userspace creates
any vcpu.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 579ce34e7904..1d5a7f418795 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -87,6 +87,11 @@ EXPORT_SYMBOL_GPL(kvm_x86_ops);
 int ignore_msrs = 0;
 module_param_named(ignore_msrs, ignore_msrs, bool, S_IRUGO | S_IWUSR);
 
+bool kvm_has_tsc_control;
+EXPORT_SYMBOL_GPL(kvm_has_tsc_control);
+u32  kvm_max_guest_tsc_khz;
+EXPORT_SYMBOL_GPL(kvm_max_guest_tsc_khz);
+
 #define KVM_NR_SHARED_MSRS 16
 
 struct kvm_shared_msrs_global {
@@ -1986,6 +1991,7 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_X86_ROBUST_SINGLESTEP:
         case KVM_CAP_XSAVE:
         case KVM_CAP_ASYNC_PF:
+        case KVM_CAP_GET_TSC_KHZ:
                 r = 1;
                 break;
         case KVM_CAP_COALESCED_MMIO:
@@ -2012,6 +2018,9 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_XCRS:
                 r = cpu_has_xsave;
                 break;
+        case KVM_CAP_TSC_CONTROL:
+                r = kvm_has_tsc_control;
+                break;
         default:
                 r = 0;
                 break;
@@ -3045,6 +3054,32 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
                 r = kvm_vcpu_ioctl_x86_set_xcrs(vcpu, u.xcrs);
                 break;
         }
+        case KVM_SET_TSC_KHZ: {
+                u32 user_tsc_khz;
+
+                r = -EINVAL;
+                if (!kvm_has_tsc_control)
+                        break;
+
+                user_tsc_khz = (u32)arg;
+
+                if (user_tsc_khz >= kvm_max_guest_tsc_khz)
+                        goto out;
+
+                kvm_x86_ops->set_tsc_khz(vcpu, user_tsc_khz);
+
+                r = 0;
+                goto out;
+        }
+        case KVM_GET_TSC_KHZ: {
+                r = -EIO;
+                if (check_tsc_unstable())
+                        goto out;
+
+                r = vcpu_tsc_khz(vcpu);
+
+                goto out;
+        }
         default:
                 r = -EINVAL;
         }