[PATCH v1 20/28] x86/hvm: rework XEN_DOMCTL_debug_op

[dmukhin@xxxxxxxx]

From: Denis Mukhin <dmukhin@xxxxxxxx>

Currently, XEN_DOMCTL_debug_op assumes operations on VCPUs only
and only for Intel VMX-supported HVM domains. This limits its
usability in the test infrastructure.

Generalize XEN_DOMCTL_debug_op to allow operations on any x86 HVM
domain.

Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
 xen/arch/x86/domctl.c              | 24 ++++--------
 xen/arch/x86/hvm/hvm.c             | 59 ++++++++++++++++++++----------
 xen/arch/x86/include/asm/hvm/hvm.h |  3 +-
 xen/include/public/domctl.h        |  1 +
 4 files changed, 49 insertions(+), 38 deletions(-)

diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index 12c14bb3f514..7a52aff71620 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -912,23 +912,13 @@ long arch_do_domctl(
 
     case XEN_DOMCTL_debug_op:
     {
-        struct vcpu *v;
-
-        ret = -EOPNOTSUPP;
-        if ( !IS_ENABLED(CONFIG_HVM) )
-            break;
-
-        ret = -EINVAL;
-        if ( (domctl->u.debug_op.vcpu >= d->max_vcpus) ||
-             ((v = d->vcpu[domctl->u.debug_op.vcpu]) == NULL) )
-            break;
-
-        ret = -EINVAL;
-        if ( (v == curr) || /* no vcpu_pause() */
-             !is_hvm_domain(d) )
-            break;
-
-        ret = hvm_debug_op(v, domctl->u.debug_op.op);
+        if ( IS_ENABLED(CONFIG_HVM) )
+            ret = hvm_debug_op(d,
+                               domctl->u.debug_op.op,
+                               domctl->u.debug_op.vcpu,
+                               domctl->u.debug_op.arg);
+        else
+            ret = -EOPNOTSUPP;
         break;
     }
 
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index ef9c7cd05777..42139837904a 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -5200,32 +5200,52 @@ long do_hvm_op(unsigned long op, 
XEN_GUEST_HANDLE_PARAM(void) arg)
     return rc;
 }
 
-int hvm_debug_op(struct vcpu *v, int32_t op)
+static int hvm_debug_op_single_step_allowed(const struct domain *d,
+                                            unsigned int vcpu)
 {
+    if ( (vcpu >= d->max_vcpus) || (d->vcpu[vcpu] == NULL) )
+        return -EINVAL;
+
+    if ( (d->vcpu[vcpu] == current) || /* no vcpu_pause() */
+         !is_hvm_domain(d) )
+        return -EINVAL;
+
+    if ( !IS_ENABLED(CONFIG_INTEL_VMX) || !cpu_has_monitor_trap_flag )
+        return -EOPNOTSUPP;
+
+    return 0;
+}
+
+int hvm_debug_op(struct domain *d, unsigned int op, unsigned int vcpu,
+                 unsigned int arg)
+{
+    struct vcpu *v;
     int rc = 0;
 
-    switch ( op )
-    {
-        case XEN_DOMCTL_DEBUG_OP_SINGLE_STEP_ON:
-        case XEN_DOMCTL_DEBUG_OP_SINGLE_STEP_OFF:
-            if ( !cpu_has_monitor_trap_flag )
-                return -EOPNOTSUPP;
-            break;
-        default:
-            return -ENOSYS;
-    }
-
-    BUILD_ERROR_IF_NOT(CONFIG_INTEL_VMX);
-
-    vcpu_pause(v);
-
     switch ( op )
     {
     case XEN_DOMCTL_DEBUG_OP_SINGLE_STEP_ON:
+        rc = hvm_debug_op_single_step_allowed(d, vcpu);
+        if ( rc )
+            break;
+
+        v = d->vcpu[vcpu];
+
+        vcpu_pause(v);
         v->arch.hvm.single_step = true;
+        vcpu_unpause(v); /* guest will latch new state */
+
         break;
 
     case XEN_DOMCTL_DEBUG_OP_SINGLE_STEP_OFF:
+        rc = hvm_debug_op_single_step_allowed(d, vcpu);
+        if ( rc )
+            break;
+
+        v = d->vcpu[vcpu];
+
+        vcpu_pause(v);
+
         v->arch.hvm.single_step = false;
 
 #ifdef CONFIG_ALTP2M
@@ -5233,15 +5253,14 @@ int hvm_debug_op(struct vcpu *v, int32_t op)
         v->arch.hvm.fast_single_step.p2midx = 0;
 #endif
 
+        vcpu_unpause(v); /* guest will latch new state */
+
         break;
 
-    default: /* Excluded above */
-        ASSERT_UNREACHABLE();
+    default:
         return -ENOSYS;
     }
 
-    vcpu_unpause(v); /* guest will latch new state */
-
     return rc;
 }
 
diff --git a/xen/arch/x86/include/asm/hvm/hvm.h 
b/xen/arch/x86/include/asm/hvm/hvm.h
index 1f0f7749b579..6efc533b35df 100644
--- a/xen/arch/x86/include/asm/hvm/hvm.h
+++ b/xen/arch/x86/include/asm/hvm/hvm.h
@@ -369,7 +369,8 @@ void *hvm_map_guest_frame_ro(unsigned long gfn, bool 
permanent);
 void hvm_unmap_guest_frame(void *p, bool permanent);
 void hvm_mapped_guest_frames_mark_dirty(struct domain *d);
 
-int hvm_debug_op(struct vcpu *v, int32_t op);
+int hvm_debug_op(struct domain *d, unsigned int op, unsigned int vcpu,
+                 unsigned int arg);
 
 /* Caller should pause vcpu before calling this function */
 void hvm_toggle_singlestep(struct vcpu *v);
diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 4ca8a2d7ca65..546d9a8ac9c0 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -768,6 +768,7 @@ struct xen_domctl_subscribe {
 struct xen_domctl_debug_op {
     uint32_t op;   /* IN */
     uint32_t vcpu; /* IN */
+    uint32_t arg;  /* IN */
 };
 
 /*
-- 
2.55.0