KVM: local APIC TPR access reporting facility

Add a facility to report on accesses to the local apic tpr even if the
local apic is emulated in the kernel.  This is basically a hack that
allows userspace to patch Windows which tends to bang on the tpr a lot.

Signed-off-by: Avi Kivity <avi@qumranet.com>

2 files changed, 46 insertions, 0 deletions

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 4076331b01ee..50c3f3a8dd3d 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -551,6 +551,23 @@ static u32 apic_get_tmcct(struct kvm_lapic *apic)
         return tmcct;
 }
 
+static void __report_tpr_access(struct kvm_lapic *apic, bool write)
+{
+        struct kvm_vcpu *vcpu = apic->vcpu;
+        struct kvm_run *run = vcpu->run;
+
+        set_bit(KVM_REQ_REPORT_TPR_ACCESS, &vcpu->requests);
+        kvm_x86_ops->cache_regs(vcpu);
+        run->tpr_access.rip = vcpu->arch.rip;
+        run->tpr_access.is_write = write;
+}
+
+static inline void report_tpr_access(struct kvm_lapic *apic, bool write)
+{
+        if (apic->vcpu->arch.tpr_access_reporting)
+                __report_tpr_access(apic, write);
+}
+
 static u32 __apic_read(struct kvm_lapic *apic, unsigned int offset)
 {
         u32 val = 0;
@@ -568,6 +585,9 @@ static u32 __apic_read(struct kvm_lapic *apic, unsigned int offset)
                 val = apic_get_tmcct(apic);
                 break;
 
+        case APIC_TASKPRI:
+                report_tpr_access(apic, false);
+                /* fall thru */
         default:
                 apic_update_ppr(apic);
                 val = apic_get_reg(apic, offset);
@@ -677,6 +697,7 @@ static void apic_mmio_write(struct kvm_io_device *this,
                 break;
 
         case APIC_TASKPRI:
+                report_tpr_access(apic, true);
                 apic_set_tpr(apic, val & 0xff);
                 break;
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 513258c797ca..c2b80884447e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -684,6 +684,7 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_USER_MEMORY:
         case KVM_CAP_SET_TSS_ADDR:
         case KVM_CAP_EXT_CPUID:
+        case KVM_CAP_VAPIC:
                 r = 1;
                 break;
         default:
@@ -1055,6 +1056,15 @@ static int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu,
         return 0;
 }
 
+static int vcpu_ioctl_tpr_access_reporting(struct kvm_vcpu *vcpu,
+                                           struct kvm_tpr_access_ctl *tac)
+{
+        if (tac->flags)
+                return -EINVAL;
+        vcpu->arch.tpr_access_reporting = !!tac->enabled;
+        return 0;
+}
+
 long kvm_arch_vcpu_ioctl(struct file *filp,
                          unsigned int ioctl, unsigned long arg)
 {
@@ -1148,6 +1158,21 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
         case KVM_SET_MSRS:
                 r = msr_io(vcpu, argp, do_set_msr, 0);
                 break;
+        case KVM_TPR_ACCESS_REPORTING: {
+                struct kvm_tpr_access_ctl tac;
+
+                r = -EFAULT;
+                if (copy_from_user(&tac, argp, sizeof tac))
+                        goto out;
+                r = vcpu_ioctl_tpr_access_reporting(vcpu, &tac);
+                if (r)
+                        goto out;
+                r = -EFAULT;
+                if (copy_to_user(argp, &tac, sizeof tac))
+                        goto out;
+                r = 0;
+                break;
+        };
         default:
                 r = -EINVAL;
         }