From ec70614e30f5b38cc958fcf2c034a7d58dcc5190 Mon Sep 17 00:00:00 2001
From: Jan Beulich <jbeulich@suse.com>
Date: Tue, 15 Dec 2015 15:36:01 +0100
Subject: [PATCH 12/43] 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>
master commit: 81a28f14009f4d8577a81b28dd06f6828112054b
master date: 2015-11-24 12:30:31 +0100
---
 xen/arch/x86/hvm/vmx/vmx.c | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 4540cdc..bfc6465 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -1463,16 +1463,7 @@ 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) )
-        current->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 )
@@ -1480,6 +1471,16 @@ static void vmx_inject_trap(struct hvm_trap *trap)
             __restore_debug_registers(curr);
             write_debugreg(6, read_debugreg(6) | 0x4000);
         }
+        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 */
@@ -1490,8 +1491,19 @@ 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) &&
          (((intr_info >> 8) & 7) == X86_EVENTTYPE_HW_EXCEPTION) )
     {
-- 
2.7.2