x86/hvm: Avoid __hvm_copy() raising #PF behind the emulators back

Drop the call to hvm_inject_page_fault() in __hvm_copy(), and require callers
to inject the pagefault themselves.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Tim Deegan <tim@xen.org>
Acked-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>

xen/arch/x86/hvm/emulate.c

@@ -799,6 +799,7 @@ static int __hvmemul_read(
     case HVMCOPY_okay:
         break;
     case HVMCOPY_bad_gva_to_gfn:
+        x86_emul_pagefault(pfinfo.ec, pfinfo.linear, &hvmemul_ctxt->ctxt);
         return X86EMUL_EXCEPTION;
     case HVMCOPY_bad_gfn_to_mfn:
         if ( access_type == hvm_access_insn_fetch )
@@ -905,6 +906,7 @@ static int hvmemul_write(
     case HVMCOPY_okay:
         break;
     case HVMCOPY_bad_gva_to_gfn:
+        x86_emul_pagefault(pfinfo.ec, pfinfo.linear, &hvmemul_ctxt->ctxt);
         return X86EMUL_EXCEPTION;
     case HVMCOPY_bad_gfn_to_mfn:
         return hvmemul_linear_mmio_write(addr, bytes, p_data, pfec, hvmemul_ctxt, 0);

xen/arch/x86/hvm/hvm.c

@@ -2927,6 +2927,8 @@ void hvm_task_switch(
 
     rc = hvm_copy_from_guest_linear(
         &tss, prev_tr.base, sizeof(tss), PFEC_page_present, &pfinfo);
+    if ( rc == HVMCOPY_bad_gva_to_gfn )
+        hvm_inject_page_fault(pfinfo.ec, pfinfo.linear);
     if ( rc != HVMCOPY_okay )
         goto out;
 
@@ -2965,11 +2967,15 @@ void hvm_task_switch(
                                   offsetof(typeof(tss), trace) -
                                   offsetof(typeof(tss), eip),
                                   PFEC_page_present, &pfinfo);
+    if ( rc == HVMCOPY_bad_gva_to_gfn )
+        hvm_inject_page_fault(pfinfo.ec, pfinfo.linear);
     if ( rc != HVMCOPY_okay )
         goto out;
 
     rc = hvm_copy_from_guest_linear(
         &tss, tr.base, sizeof(tss), PFEC_page_present, &pfinfo);
+    if ( rc == HVMCOPY_bad_gva_to_gfn )
+        hvm_inject_page_fault(pfinfo.ec, pfinfo.linear);
     /*
      * Note: The HVMCOPY_gfn_shared case could be optimised, if the callee
      * functions knew we want RO access.
@@ -3012,7 +3018,10 @@ void hvm_task_switch(
                                       &tss.back_link, sizeof(tss.back_link), 0,
                                       &pfinfo);
         if ( rc == HVMCOPY_bad_gva_to_gfn )
+        {
+            hvm_inject_page_fault(pfinfo.ec, pfinfo.linear);
             exn_raised = 1;
+        }
         else if ( rc != HVMCOPY_okay )
             goto out;
     }
@@ -3050,7 +3059,10 @@ void hvm_task_switch(
             rc = hvm_copy_to_guest_linear(linear_addr, &errcode, opsz, 0,
                                           &pfinfo);
             if ( rc == HVMCOPY_bad_gva_to_gfn )
+            {
+                hvm_inject_page_fault(pfinfo.ec, pfinfo.linear);
                 exn_raised = 1;
+            }
             else if ( rc != HVMCOPY_okay )
                 goto out;
         }
@@ -3114,8 +3126,6 @@ static enum hvm_copy_result __hvm_copy(
                 {
                     pfinfo->linear = addr;
                     pfinfo->ec = pfec;
-
-                    hvm_inject_page_fault(pfec, addr);
                 }
                 return HVMCOPY_bad_gva_to_gfn;
             }

xen/arch/x86/hvm/vmx/vvmx.c

@@ -396,7 +396,6 @@ static int decode_vmx_inst(struct cpu_user_regs *regs,
     struct vcpu *v = current;
     union vmx_inst_info info;
     struct segment_register seg;
-    pagefault_info_t pfinfo;
     unsigned long base, index, seg_base, disp, offset;
     int scale, size;
 
@@ -451,10 +450,17 @@ static int decode_vmx_inst(struct cpu_user_regs *regs,
               offset + size - 1 > seg.limit) )
             goto gp_fault;
 
-        if ( poperandS != NULL &&
-             hvm_copy_from_guest_linear(poperandS, base, size, 0, &pfinfo)
-                  != HVMCOPY_okay )
-            return X86EMUL_EXCEPTION;
+        if ( poperandS != NULL )
+        {
+            pagefault_info_t pfinfo;
+            int rc = hvm_copy_from_guest_linear(poperandS, base, size,
+                                                0, &pfinfo);
+
+            if ( rc == HVMCOPY_bad_gva_to_gfn )
+                hvm_inject_page_fault(pfinfo.ec, pfinfo.linear);
+            if ( rc != HVMCOPY_okay )
+                return X86EMUL_EXCEPTION;
+        }
         decode->mem = base;
         decode->len = size;
     }
@@ -1623,6 +1629,8 @@ int nvmx_handle_vmptrst(struct cpu_user_regs *regs)
     gpa = nvcpu->nv_vvmcxaddr;
 
     rc = hvm_copy_to_guest_linear(decode.mem, &gpa, decode.len, 0, &pfinfo);
+    if ( rc == HVMCOPY_bad_gva_to_gfn )
+        hvm_inject_page_fault(pfinfo.ec, pfinfo.linear);
     if ( rc != HVMCOPY_okay )
         return X86EMUL_EXCEPTION;
 
@@ -1694,6 +1702,8 @@ int nvmx_handle_vmread(struct cpu_user_regs *regs)
     switch ( decode.type ) {
     case VMX_INST_MEMREG_TYPE_MEMORY:
         rc = hvm_copy_to_guest_linear(decode.mem, &value, decode.len, 0, &pfinfo);
+        if ( rc == HVMCOPY_bad_gva_to_gfn )
+            hvm_inject_page_fault(pfinfo.ec, pfinfo.linear);
         if ( rc != HVMCOPY_okay )
             return X86EMUL_EXCEPTION;
         break;

xen/arch/x86/mm/shadow/common.c

@@ -198,6 +198,7 @@ hvm_read(enum x86_segment seg,
     case HVMCOPY_okay:
         return X86EMUL_OKAY;
     case HVMCOPY_bad_gva_to_gfn:
+        x86_emul_pagefault(pfinfo.ec, pfinfo.linear, &sh_ctxt->ctxt);
         return X86EMUL_EXCEPTION;
     case HVMCOPY_bad_gfn_to_mfn:
     case HVMCOPY_unhandleable:

xen/include/asm-x86/hvm/support.h

@@ -85,9 +85,7 @@ enum hvm_copy_result hvm_copy_from_guest_phys(
  *  HVMCOPY_bad_gva_to_gfn: Some guest virtual address did not have a valid
  *                          mapping to a guest physical address.  The
  *                          pagefault_info_t structure will be filled in if
- *                          provided, and a page fault exception is
- *                          automatically queued for injection into the
- *                          current HVM VCPU.
+ *                          provided.
  */
 typedef struct pagefault_info
 {