KVM: x86: Add support for saving&restoring debug registers

So far user space was not able to save and restore debug registers for
migration or after reset. Plug this hole.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/Documentation/kvm/api.txt b/Documentation/kvm/api.txt
index 9e5de5a..d170cb4 100644 (file)
--- a/Documentation/kvm/api.txt
+++ b/Documentation/kvm/api.txt
@@ -718,6 +718,37 @@ If KVM_CAP_INTR_SHADOW is available, KVM_VCPUEVENT_VALID_SHADOW can be set in
 the flags field to signal that interrupt.shadow contains a valid state and
 shall be written into the VCPU.
 
+4.32 KVM_GET_DEBUGREGS
+
+Capability: KVM_CAP_DEBUGREGS
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_debugregs (out)
+Returns: 0 on success, -1 on error
+
+Reads debug registers from the vcpu.
+
+struct kvm_debugregs {
+       __u64 db[4];
+       __u64 dr6;
+       __u64 dr7;
+       __u64 flags;
+       __u64 reserved[9];
+};
+
+4.33 KVM_SET_DEBUGREGS
+
+Capability: KVM_CAP_DEBUGREGS
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_debugregs (in)
+Returns: 0 on success, -1 on error
+
+Writes debug registers into the vcpu.
+
+See KVM_GET_DEBUGREGS for the data structure. The flags field is unused
+yet and must be cleared on entry.
+
 
 5. The kvm_run structure
 

diff --git a/arch/x86/include/asm/kvm.h b/arch/x86/include/asm/kvm.h
index fb61170..ff90055 100644 (file)
--- a/arch/x86/include/asm/kvm.h
+++ b/arch/x86/include/asm/kvm.h
@@ -21,6 +21,7 @@
 #define __KVM_HAVE_PIT_STATE2
 #define __KVM_HAVE_XEN_HVM
 #define __KVM_HAVE_VCPU_EVENTS
+#define __KVM_HAVE_DEBUGREGS
 
 /* Architectural interrupt line count. */
 #define KVM_NR_INTERRUPTS 256
@@ -289,4 +290,13 @@ struct kvm_vcpu_events {
        __u32 reserved[10];
 };
 
+/* for KVM_GET/SET_DEBUGREGS */
+struct kvm_debugregs {
+       __u64 db[4];
+       __u64 dr6;
+       __u64 dr7;
+       __u64 flags;
+       __u64 reserved[9];
+};
+
 #endif /* _ASM_X86_KVM_H */

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 84ffd95..efeeabd 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1548,6 +1548,7 @@ int kvm_dev_ioctl_check_extension(long ext)
        case KVM_CAP_HYPERV_VAPIC:
        case KVM_CAP_HYPERV_SPIN:
        case KVM_CAP_PCI_SEGMENT:
+       case KVM_CAP_DEBUGREGS:
        case KVM_CAP_X86_ROBUST_SINGLESTEP:
                r = 1;
                break;
@@ -2165,6 +2166,36 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
        return 0;
 }
 
+static void kvm_vcpu_ioctl_x86_get_debugregs(struct kvm_vcpu *vcpu,
+                                            struct kvm_debugregs *dbgregs)
+{
+       vcpu_load(vcpu);
+
+       memcpy(dbgregs->db, vcpu->arch.db, sizeof(vcpu->arch.db));
+       dbgregs->dr6 = vcpu->arch.dr6;
+       dbgregs->dr7 = vcpu->arch.dr7;
+       dbgregs->flags = 0;
+
+       vcpu_put(vcpu);
+}
+
+static int kvm_vcpu_ioctl_x86_set_debugregs(struct kvm_vcpu *vcpu,
+                                           struct kvm_debugregs *dbgregs)
+{
+       if (dbgregs->flags)
+               return -EINVAL;
+
+       vcpu_load(vcpu);
+
+       memcpy(vcpu->arch.db, dbgregs->db, sizeof(vcpu->arch.db));
+       vcpu->arch.dr6 = dbgregs->dr6;
+       vcpu->arch.dr7 = dbgregs->dr7;
+
+       vcpu_put(vcpu);
+
+       return 0;
+}
+
 long kvm_arch_vcpu_ioctl(struct file *filp,
                         unsigned int ioctl, unsigned long arg)
 {
@@ -2343,6 +2374,29 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
                r = kvm_vcpu_ioctl_x86_set_vcpu_events(vcpu, &events);
                break;
        }
+       case KVM_GET_DEBUGREGS: {
+               struct kvm_debugregs dbgregs;
+
+               kvm_vcpu_ioctl_x86_get_debugregs(vcpu, &dbgregs);
+
+               r = -EFAULT;
+               if (copy_to_user(argp, &dbgregs,
+                                sizeof(struct kvm_debugregs)))
+                       break;
+               r = 0;
+               break;
+       }
+       case KVM_SET_DEBUGREGS: {
+               struct kvm_debugregs dbgregs;
+
+               r = -EFAULT;
+               if (copy_from_user(&dbgregs, argp,
+                                  sizeof(struct kvm_debugregs)))
+                       break;
+
+               r = kvm_vcpu_ioctl_x86_set_debugregs(vcpu, &dbgregs);
+               break;
+       }
        default:
                r = -EINVAL;
        }

diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 48516a2..ce28767 100644 (file)
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -503,6 +503,9 @@ struct kvm_ioeventfd {
 #define KVM_CAP_PCI_SEGMENT 47
 #define KVM_CAP_PPC_PAIRED_SINGLES 48
 #define KVM_CAP_INTR_SHADOW 49
+#ifdef __KVM_HAVE_DEBUGREGS
+#define KVM_CAP_DEBUGREGS 50
+#endif
 #define KVM_CAP_X86_ROBUST_SINGLESTEP 51
 
 #ifdef KVM_CAP_IRQ_ROUTING
@@ -690,6 +693,9 @@ struct kvm_clock_data {
 /* Available with KVM_CAP_VCPU_EVENTS */
 #define KVM_GET_VCPU_EVENTS       _IOR(KVMIO,  0x9f, struct kvm_vcpu_events)
 #define KVM_SET_VCPU_EVENTS       _IOW(KVMIO,  0xa0, struct kvm_vcpu_events)
+/* Available with KVM_CAP_DEBUGREGS */
+#define KVM_GET_DEBUGREGS         _IOR(KVMIO,  0xa1, struct kvm_debugregs)
+#define KVM_SET_DEBUGREGS         _IOW(KVMIO,  0xa2, struct kvm_debugregs)
 
 #define KVM_DEV_ASSIGN_ENABLE_IOMMU    (1 << 0)