VMX: fix/adjust trap injection

In the course of investigating the 4.1.6 backport issue of the XSA-156
patch I realized that #DB injection has always been broken, but with it
now getting always intercepted the problem has got worse: Documentation
clearly states that neither DR7.GD nor DebugCtl.LBR get cleared before
the intercept, so this is something we need to do before reflecting the
intercepted exception.

While adjusting this (and also with 4.1.6's strange use of
X86_EVENTTYPE_SW_EXCEPTION for #DB in mind) I further realized that
the special casing of individual vectors shouldn't be done for
software interrupts (resulting from INT $nn).

And then some code movement: Setting of CR2 for #PF can be done in the
same switch() statement (no need for a separate if()), and reading of
intr_info is better done close the the consumption of the variable
(allowing the compiler to generate better code / use fewer registers
for variables).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 4b8d2fa85929b8ab1d124a09ef338fd7c10ad019..326d80313c208bff67ae64106e85f005c05f03b7 100644 (file)
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -1506,16 +1506,7 @@ static void vmx_inject_trap(struct hvm_trap *trap)
     struct vcpu *curr = current;
     struct hvm_trap _trap = *trap;
 
-    if ( (_trap.vector == TRAP_page_fault) &&
-         (_trap.type == X86_EVENTTYPE_HW_EXCEPTION) )
-        curr->arch.hvm_vcpu.guest_cr[2] = _trap.cr2;
-
-    if ( nestedhvm_vcpu_in_guestmode(curr) )
-        intr_info = vcpu_2_nvmx(curr).intr.intr_info;
-    else
-        __vmread(VM_ENTRY_INTR_INFO, &intr_info);
-
-    switch ( _trap.vector )
+    switch ( _trap.vector | -(_trap.type == X86_EVENTTYPE_SW_INTERRUPT) )
     {
     case TRAP_debug:
         if ( guest_cpu_user_regs()->eflags & X86_EFLAGS_TF )
@@ -1523,6 +1514,16 @@ static void vmx_inject_trap(struct hvm_trap *trap)
             __restore_debug_registers(curr);
             write_debugreg(6, read_debugreg(6) | DR_STEP);
         }
+        if ( !nestedhvm_vcpu_in_guestmode(curr) ||
+             !nvmx_intercepts_exception(curr, TRAP_debug, _trap.error_code) )
+        {
+            unsigned long val;
+
+            __vmread(GUEST_DR7, &val);
+            __vmwrite(GUEST_DR7, val & ~DR_GENERAL_DETECT);
+            __vmread(GUEST_IA32_DEBUGCTL, &val);
+            __vmwrite(GUEST_IA32_DEBUGCTL, val & ~IA32_DEBUGCTLMSR_LBR);
+        }
         if ( cpu_has_monitor_trap_flag )
             break;
         /* fall through */
@@ -1533,8 +1534,19 @@ static void vmx_inject_trap(struct hvm_trap *trap)
             domain_pause_for_debugger();
             return;
         }
+        break;
+
+    case TRAP_page_fault:
+        ASSERT(_trap.type == X86_EVENTTYPE_HW_EXCEPTION);
+        curr->arch.hvm_vcpu.guest_cr[2] = _trap.cr2;
+        break;
     }
 
+    if ( nestedhvm_vcpu_in_guestmode(curr) )
+        intr_info = vcpu_2_nvmx(curr).intr.intr_info;
+    else
+        __vmread(VM_ENTRY_INTR_INFO, &intr_info);
+
     if ( unlikely(intr_info & INTR_INFO_VALID_MASK) &&
          (MASK_EXTR(intr_info, INTR_INFO_INTR_TYPE_MASK) ==
           X86_EVENTTYPE_HW_EXCEPTION) )