[PATCH 6/7] x86: Extend x86_event with a pending_dbg field

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

... using the Intel VMCS PENDING_DBG semantics, and sharing storage with cr2.

This requires working around anonymous union bugs in obsolete versions of GCC,
which in turn needs to drop unnecessary const qualifiers.

Also introduce a pv_inject_DB() wrapper use this field nicely.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Jinoh Kang <jinoh.kang.kr@xxxxxxxxx>

v2:
 * Split out of prior patch.
---
 xen/arch/x86/include/asm/domain.h      | 18 ++++++++++++++++--
 xen/arch/x86/include/asm/hvm/hvm.h     |  3 ++-
 xen/arch/x86/x86_emulate/x86_emulate.h |  5 ++++-
 3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/include/asm/domain.h 
b/xen/arch/x86/include/asm/domain.h
index c2d9fc333be5..fd1f306222be 100644
--- a/xen/arch/x86/include/asm/domain.h
+++ b/xen/arch/x86/include/asm/domain.h
@@ -729,15 +729,29 @@ static inline void pv_inject_hw_exception(unsigned int 
vector, int errcode)
     pv_inject_event(&event);
 }
 
+static inline void pv_inject_DB(unsigned long pending_dbg)
+{
+    struct x86_event event = {
+        .vector      = X86_EXC_DB,
+        .type        = X86_EVENTTYPE_HW_EXCEPTION,
+        .error_code  = X86_EVENT_NO_EC,
+    };
+
+    event.pending_dbg = pending_dbg;
+
+    pv_inject_event(&event);
+}
+
 static inline void pv_inject_page_fault(int errcode, unsigned long cr2)
 {
-    const struct x86_event event = {
+    struct x86_event event = {
         .vector = X86_EXC_PF,
         .type = X86_EVENTTYPE_HW_EXCEPTION,
         .error_code = errcode,
-        .cr2 = cr2,
     };
 
+    event.cr2 = cr2;
+
     pv_inject_event(&event);
 }
 
diff --git a/xen/arch/x86/include/asm/hvm/hvm.h 
b/xen/arch/x86/include/asm/hvm/hvm.h
index 6d53713fc3a9..ea966f4429f9 100644
--- a/xen/arch/x86/include/asm/hvm/hvm.h
+++ b/xen/arch/x86/include/asm/hvm/hvm.h
@@ -532,9 +532,10 @@ static inline void hvm_inject_page_fault(int errcode, 
unsigned long cr2)
         .vector = X86_EXC_PF,
         .type = X86_EVENTTYPE_HW_EXCEPTION,
         .error_code = errcode,
-        .cr2 = cr2,
     };
 
+    event.cr2 = cr2;
+
     hvm_inject_event(&event);
 }
 
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.h 
b/xen/arch/x86/x86_emulate/x86_emulate.h
index fbc023c37e34..e567a9b635d9 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.h
+++ b/xen/arch/x86/x86_emulate/x86_emulate.h
@@ -78,7 +78,10 @@ struct x86_event {
     uint8_t       type;         /* X86_EVENTTYPE_* */
     uint8_t       insn_len;     /* Instruction length */
     int32_t       error_code;   /* X86_EVENT_NO_EC if n/a */
-    unsigned long cr2;          /* Only for X86_EXC_PF h/w exception */
+    union {
+        unsigned long cr2;         /* #PF */
+        unsigned long pending_dbg; /* #DB (new DR6 bits, positive polarity) */
+    };
 };
 
 /*
-- 
2.30.2