[Xen-devel] [PATCH 09/15] x86/emul: Avoid raising faults behind the emulators back

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Introduce a new x86_emul_pagefault() similar to x86_emul_hw_exception(), and
use this instead of hvm_inject_page_fault() from emulation codepaths.

Replace one hvm_inject_hw_exception() in the shadow emulation codepaths.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Paul Durrant <paul.durrant@xxxxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
CC: George Dunlap <george.dunlap@xxxxxxxxxxxxx>

NOTE: this is a functional change for the shadow code, as a #PF previously
raised properly with the guest will now cause X86EMUL_UNHANDLABLE. It is my
understanding after a discusion with Tim that this is ok, but I haven't done
extenstive testing yet.
---
 xen/arch/x86/hvm/emulate.c             |  4 ++--
 xen/arch/x86/mm/shadow/common.c        |  5 +++--
 xen/arch/x86/x86_emulate/x86_emulate.h | 13 +++++++++++++
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index c0fbde1..3ebb200 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -459,7 +459,7 @@ static int hvmemul_linear_to_phys(
     {
         if ( pfec & (PFEC_page_paged | PFEC_page_shared) )
             return X86EMUL_RETRY;
-        hvm_inject_page_fault(pfec, addr);
+        x86_emul_pagefault(pfec, addr, &hvmemul_ctxt->ctxt);
         return X86EMUL_EXCEPTION;
     }
 
@@ -483,7 +483,7 @@ static int hvmemul_linear_to_phys(
                 ASSERT(!reverse);
                 if ( npfn != gfn_x(INVALID_GFN) )
                     return X86EMUL_UNHANDLEABLE;
-                hvm_inject_page_fault(pfec, addr & PAGE_MASK);
+                x86_emul_pagefault(pfec, addr & PAGE_MASK, 
&hvmemul_ctxt->ctxt);
                 return X86EMUL_EXCEPTION;
             }
             *reps = done;
diff --git a/xen/arch/x86/mm/shadow/common.c b/xen/arch/x86/mm/shadow/common.c
index 6f6668d..c8b61b9 100644
--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -162,8 +162,9 @@ static int hvm_translate_linear_addr(
 
     if ( !okay )
     {
-        hvm_inject_hw_exception(
-            (seg == x86_seg_ss) ? TRAP_stack_error : TRAP_gp_fault, 0);
+        x86_emul_hw_exception(
+            (seg == x86_seg_ss) ? TRAP_stack_error : TRAP_gp_fault,
+            0, &sh_ctxt->ctxt);
         return X86EMUL_EXCEPTION;
     }
 
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.h 
b/xen/arch/x86/x86_emulate/x86_emulate.h
index ddcd93c..cc26e9d 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.h
+++ b/xen/arch/x86/x86_emulate/x86_emulate.h
@@ -600,6 +600,19 @@ static inline void x86_emul_hw_exception(
     ctxt->event_pending = true;
 }
 
+static inline void x86_emul_pagefault(
+    unsigned int error_code, unsigned long cr2, struct x86_emulate_ctxt *ctxt)
+{
+    ASSERT(!ctxt->event_pending);
+
+    ctxt->event.vector = 14; /* TRAP_page_fault */
+    ctxt->event.type = X86_EVENTTYPE_HW_EXCEPTION;
+    ctxt->event.error_code = error_code;
+    ctxt->event.cr2 = cr2;
+
+    ctxt->event_pending = true;
+}
+
 static inline void x86_emul_software_event(
     enum x86_swint_type type, uint8_t vector, uint8_t insn_len,
     struct x86_emulate_ctxt *ctxt)
-- 
2.1.4


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