mem_event: Revert pointless, unrelated, and broken (on i386) change in 23434:ef410f262299

vcpu_pause() is nestable in the hypervisor, hence checking for
already-paused is not required.

Signed-off-by: Keir Fraser <keir@xen.org>
xen-unstable changeset:   23435:c15f06b99bbe
xen-unstable date:        Sat May 28 08:33:54 2011 +0100


mem_event: Allow memory access listener to perform single step execution.

Add a new memory event that handles single step. This allows the
memory access listener to handle instructions that modify data within
the execution page.  This can be enabled in the listener by doing:
xc_set_hvm_param(xch, domain_id, HVM_PARAM_MEMORY_EVENT_SINGLE_STEP,
HVMPME_mode_sync)

Now the listener can start single stepping by:
xc_domain_debug_control(xch, domain_id,
XEN_DOMCTL_DEBUG_OP_SINGLE_STEP_ON, vcpu_id)

And stop single stepping by: xc_domain_debug_control(xch, domain_id,
XEN_DOMCTL_DEBUG_OP_SINGLE_STEP_OFF, vcpu_id)

Signed-off-by: Aravindh Puthiyaparambil <aravindh@virtuata.com>
Acked-by: Tim Deegan <Tim.Deegan@citrix.com>
xen-unstable changeset:   23434:ef410f262299
xen-unstable date:        Fri May 27 18:44:26 2011 +0100

6 files changed, 37 insertions, 10 deletions

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index ce3caa4fcb..bb086bcb22 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3257,7 +3257,8 @@ long do_hvm_op(unsigned long op, XEN_GUEST_HANDLE(void) arg)
                     rc = -EPERM;
                 break;
             case HVM_PARAM_MEMORY_EVENT_INT3:
-                if ( d == current->domain ) 
+            case HVM_PARAM_MEMORY_EVENT_SINGLE_STEP:
+                if ( d == current->domain )
                 {
                     rc = -EPERM;
                     break;
@@ -3274,6 +3275,7 @@ long do_hvm_op(unsigned long op, XEN_GUEST_HANDLE(void) arg)
                 switch( a.index )
                 {
                 case HVM_PARAM_MEMORY_EVENT_INT3:
+                case HVM_PARAM_MEMORY_EVENT_SINGLE_STEP:
                 {
                     domain_pause(d);
                     domain_unpause(d); /* Causes guest to latch new status */
@@ -3885,6 +3887,18 @@ int hvm_memory_event_int3(unsigned long gla)
                                   MEM_EVENT_REASON_INT3,
                                   gfn, 0, 1, gla);
 }
+
+int hvm_memory_event_single_step(unsigned long gla)
+{
+    uint32_t pfec = PFEC_page_present;
+    unsigned long gfn;
+    gfn = paging_gva_to_gfn(current, gla, &pfec);
+
+    return hvm_memory_event_traps(current->domain->arch.hvm_domain
+            .params[HVM_PARAM_MEMORY_EVENT_SINGLE_STEP],
+            MEM_EVENT_REASON_SINGLESTEP,
+            gfn, 0, 1, gla);
+}
 #endif /* __x86_64__ */
 
 /*
diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 18e7055157..e51dcdaf11 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -1083,8 +1083,9 @@ void vmx_do_resume(struct vcpu *v)
         hvm_asid_flush_vcpu(v);
     }
 
-    debug_state = v->domain->debugger_attached 
-                  || v->domain->arch.hvm_domain.params[HVM_PARAM_MEMORY_EVENT_INT3];
+    debug_state = v->domain->debugger_attached
+                  || v->domain->arch.hvm_domain.params[HVM_PARAM_MEMORY_EVENT_INT3]
+                  || v->domain->arch.hvm_domain.params[HVM_PARAM_MEMORY_EVENT_SINGLE_STEP];
 
     if ( unlikely(v->arch.hvm_vcpu.debug_state_latch != debug_state) )
     {
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index cd5545b368..ab903a354b 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2626,8 +2626,12 @@ asmlinkage void vmx_vmexit_handler(struct cpu_user_regs *regs)
     case EXIT_REASON_MONITOR_TRAP_FLAG:
         v->arch.hvm_vmx.exec_control &= ~CPU_BASED_MONITOR_TRAP_FLAG;
         vmx_update_cpu_exec_control(v);
-        if ( v->domain->debugger_attached && v->arch.hvm_vcpu.single_step )
-            domain_pause_for_debugger();
+        if ( v->arch.hvm_vcpu.single_step ) {
+          hvm_memory_event_single_step(regs->eip);
+          if ( v->domain->debugger_attached )
+              domain_pause_for_debugger();
+        }
+
         break;
 
     case EXIT_REASON_PAUSE_INSTRUCTION:
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index 46baf2c894..fd79ba2032 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -380,6 +380,10 @@ void hvm_memory_event_cr4(unsigned long value, unsigned long old);
 
 /* Called for current VCPU on int3: returns -1 if no listener */
 int hvm_memory_event_int3(unsigned long gla);
+
+/* Called for current VCPU on single step: returns -1 if no listener */
+int hvm_memory_event_single_step(unsigned long gla);
+
 #else
 static inline void hvm_memory_event_cr0(unsigned long value, unsigned long old)
 { }
@@ -389,6 +393,8 @@ static inline void hvm_memory_event_cr4(unsigned long value, unsigned long old)
 { }
 static inline int hvm_memory_event_int3(unsigned long gla)
 { return 0; }
+static inline int hvm_memory_event_single_step(unsigned long gla)
+{ return 0; }
 #endif
 
 #endif /* __ASM_X86_HVM_HVM_H__ */
diff --git a/xen/include/public/hvm/params.h b/xen/include/public/hvm/params.h
index 45b9a63980..1c98277d78 100644
--- a/xen/include/public/hvm/params.h
+++ b/xen/include/public/hvm/params.h
@@ -126,10 +126,11 @@
 
 /* Enable blocking memory events, async or sync (pause vcpu until response) 
  * onchangeonly indicates messages only on a change of value */
-#define HVM_PARAM_MEMORY_EVENT_CR0   20
-#define HVM_PARAM_MEMORY_EVENT_CR3   21
-#define HVM_PARAM_MEMORY_EVENT_CR4   22
-#define HVM_PARAM_MEMORY_EVENT_INT3  23
+#define HVM_PARAM_MEMORY_EVENT_CR0          20
+#define HVM_PARAM_MEMORY_EVENT_CR3          21
+#define HVM_PARAM_MEMORY_EVENT_CR4          22
+#define HVM_PARAM_MEMORY_EVENT_INT3         23
+#define HVM_PARAM_MEMORY_EVENT_SINGLE_STEP  25
 
 #define HVMPME_MODE_MASK       (3 << 0)
 #define HVMPME_mode_disabled   0
@@ -137,6 +138,6 @@
 #define HVMPME_mode_sync       2
 #define HVMPME_onchangeonly    (1 << 2)
 
-#define HVM_NR_PARAMS          24
+#define HVM_NR_PARAMS          26
 
 #endif /* __XEN_PUBLIC_HVM_PARAMS_H__ */
diff --git a/xen/include/public/mem_event.h b/xen/include/public/mem_event.h
index 93c824b867..45c15d3ef2 100644
--- a/xen/include/public/mem_event.h
+++ b/xen/include/public/mem_event.h
@@ -46,6 +46,7 @@
 #define MEM_EVENT_REASON_CR3         3    /* CR3 was hit: gfn is CR3 value */
 #define MEM_EVENT_REASON_CR4         4    /* CR4 was hit: gfn is CR4 value */
 #define MEM_EVENT_REASON_INT3        5    /* int3 was hit: gla/gfn are RIP */
+#define MEM_EVENT_REASON_SINGLESTEP  6    /* single step was invoked: gla/gfn are RIP */
 
 typedef struct mem_event_shared_page {
     uint32_t port;