[Xen-changelog] Fix injection of guest faults resulting from failed injection of a

[Xen patchbot -3.0-testing <patchbot-3.0-testing@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 24b81d9eb81c0a6b2f8acec42290536b0edf3aa4
# Parent  0d8d7071bb2fe9bb051440d3be03aa751a76510f
Fix injection of guest faults resulting from failed injection of a
previous event. We enter an infinite loop if the original failed
injection cannot be fixed up by Xen (e.g., because it's not a shadow
pagetable issue).

   The RHEL4 HVM guest hang issue was actually a side effect of
change-set 9699. In the rhel4 guest hang rc.sysinit init-script was
calls kmodule program to probe the hardware. The kmodule uses the kudzu
library call probeDevices(). For probing the graphics hardware in the
vbe_get_mode_info() function, sets up the environment and goes into the
vm86 mode to do the int x10 call. For returning back to protected mode
it sets up a int 0xff call. At the time of calling the int 0xff the
guest process pages were not filled up. And it was causing an infinite
loop of vmexits with the IDT_VECTORING_INFO on the int 0xff instruction.

        The reason for the infinite loop is changeset 9699. With that
the guest page fault was always getting overridden by the int 0xff gp
fault coming from the IDT_VECTORING_INFO. With the attached patch if VMM
is injecting exceptions like page faults or gp faults then
IDT_VECTORING_INFO field does not override it, and that breaks the
vmexit infinite loop for the rhel4.

Signed-off-by: Nitin A Kamble <nitin.a.kamble@xxxxxxxxx>
Signed-off-by: Jun Nakajima <jun.nakajima@xxxxxxxxx>
Signed-off-by: Edwin Zhai <edwin.zhai@xxxxxxxxx>

xen-unstable changeset:   9945:0c586a81d941ab0a18aecca87cffe1500a9185c5
xen-unstable date:        Fri May  5 14:05:31 2006 +0100

diff -r 0d8d7071bb2f -r 24b81d9eb81c xen/arch/x86/hvm/vmx/io.c
--- a/xen/arch/x86/hvm/vmx/io.c Fri May 05 14:02:40 2006 +0100
+++ b/xen/arch/x86/hvm/vmx/io.c Fri May 05 14:07:53 2006 +0100
@@ -166,20 +166,26 @@ asmlinkage void vmx_intr_assist(void)
     }
 
     has_ext_irq = cpu_has_pending_irq(v);
+
+    if (unlikely(v->arch.hvm_vmx.vector_injected)) {
+        v->arch.hvm_vmx.vector_injected=0;
+        if (unlikely(has_ext_irq)) enable_irq_window(v);
+        return;
+    }
+
     __vmread(IDT_VECTORING_INFO_FIELD, &idtv_info_field);
-    if (idtv_info_field & INTR_INFO_VALID_MASK) {
+    if (unlikely(idtv_info_field & INTR_INFO_VALID_MASK)) {
         __vmwrite(VM_ENTRY_INTR_INFO_FIELD, idtv_info_field);
 
         __vmread(VM_EXIT_INSTRUCTION_LEN, &inst_len);
-        if (inst_len >= 1 && inst_len <= 15)
-            __vmwrite(VM_ENTRY_INSTRUCTION_LEN, inst_len);
-
-        if (idtv_info_field & 0x800) { /* valid error code */
+        __vmwrite(VM_ENTRY_INSTRUCTION_LEN, inst_len);
+
+        if (unlikely(idtv_info_field & 0x800)) { /* valid error code */
             unsigned long error_code;
             __vmread(IDT_VECTORING_ERROR_CODE, &error_code);
             __vmwrite(VM_ENTRY_EXCEPTION_ERROR_CODE, error_code);
         }
-        if ( has_ext_irq )
+        if (unlikely(has_ext_irq))
             enable_irq_window(v);
 
         HVM_DBG_LOG(DBG_LEVEL_1, "idtv_info_field=%x", idtv_info_field);
@@ -187,8 +193,9 @@ asmlinkage void vmx_intr_assist(void)
         return;
     }
 
-    if ( !has_ext_irq ) return;
-    if ( is_interruptibility_state() ) {    /* pre-cleared for emulated 
instruction */
+    if (likely(!has_ext_irq)) return;
+
+    if (unlikely(is_interruptibility_state())) {    /* pre-cleared for 
emulated instruction */
         enable_irq_window(v);
         HVM_DBG_LOG(DBG_LEVEL_1, "interruptibility");
         return;
diff -r 0d8d7071bb2f -r 24b81d9eb81c xen/include/asm-x86/hvm/vmx/vmcs.h
--- a/xen/include/asm-x86/hvm/vmx/vmcs.h        Fri May 05 14:02:40 2006 +0100
+++ b/xen/include/asm-x86/hvm/vmx/vmcs.h        Fri May 05 14:07:53 2006 +0100
@@ -68,6 +68,7 @@ struct arch_vmx_struct {
     struct vmcs_struct      *vmcs;  /* VMCS pointer in virtual. */
     unsigned int            launch_cpu; /* VMCS is valid on this CPU. */
     u32                     exec_control; /* cache of cpu execution control */
+    u32                     vector_injected; /* if there is vector installed 
in the INTR_INFO_FIELD */
     unsigned long           flags;  /* VMCS flags */
     unsigned long           cpu_cr0; /* copy of guest CR0 */
     unsigned long           cpu_shadow_cr0; /* copy of guest read shadow CR0 */
diff -r 0d8d7071bb2f -r 24b81d9eb81c xen/include/asm-x86/hvm/vmx/vmx.h
--- a/xen/include/asm-x86/hvm/vmx/vmx.h Fri May 05 14:02:40 2006 +0100
+++ b/xen/include/asm-x86/hvm/vmx/vmx.h Fri May 05 14:07:53 2006 +0100
@@ -445,6 +445,7 @@ static inline int __vmx_inject_exception
 
 static inline int vmx_inject_exception(struct vcpu *v, int trap, int 
error_code)
 {
+    v->arch.hvm_vmx.vector_injected = 1;
     return __vmx_inject_exception(v, trap, INTR_TYPE_EXCEPTION, error_code);
 }
 

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