[Xen-changelog] [xen-3.2-testing] SVM: handle page faults in emulated instruction fetches

["Xen patchbot-3.2-testing" <patchbot-3.2-testing@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1205754053 0
# Node ID 0e23995db2eba0052f2ef05f67b845721eef65db
# Parent  28e0d4a37bb43079e5db0095a0eed70fc7fa8c13
SVM: handle page faults in emulated instruction fetches

Deal with failures in hvm_copy_from_guest_virt when fetching
instructions in the various SVM emulation paths.  Since we know that
the instruction was fetchable by the hardware, we can usually just
return from the VMEXIT and try again; whatever caused us to fail will
cause the hardware to fail next time and we'll get the correct exit
code.

Signed-off-by: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
xen-unstable changeset:   17202:8325f200e19414d998b7625f2e3cf786a6d3d3a3
xen-unstable date:        Mon Mar 17 11:39:50 2008 +0000
---
 xen/arch/x86/hvm/svm/emulate.c |    4 +++-
 xen/arch/x86/hvm/svm/svm.c     |   27 +++++++++++++++++++--------
 2 files changed, 22 insertions(+), 9 deletions(-)

diff -r 28e0d4a37bb4 -r 0e23995db2eb xen/arch/x86/hvm/svm/emulate.c
--- a/xen/arch/x86/hvm/svm/emulate.c    Wed Mar 05 16:49:33 2008 +0000
+++ b/xen/arch/x86/hvm/svm/emulate.c    Mon Mar 17 11:40:53 2008 +0000
@@ -435,7 +435,9 @@ int __get_instruction_length_from_list(s
     }
     else
     {
-        inst_copy_from_guest(buffer, svm_rip2pointer(v), MAX_INST_LEN);
+        if ( inst_copy_from_guest(buffer, svm_rip2pointer(v), MAX_INST_LEN)
+             != MAX_INST_LEN )
+            return 0;
         buf = buffer;
     }
 
diff -r 28e0d4a37bb4 -r 0e23995db2eb xen/arch/x86/hvm/svm/svm.c
--- a/xen/arch/x86/hvm/svm/svm.c        Wed Mar 05 16:49:33 2008 +0000
+++ b/xen/arch/x86/hvm/svm/svm.c        Mon Mar 17 11:40:53 2008 +0000
@@ -1128,7 +1128,7 @@ static void svm_dr_access(struct vcpu *v
 }
 
 
-static void svm_get_prefix_info(struct vcpu *v, unsigned int dir, 
+static int svm_get_prefix_info(struct vcpu *v, unsigned int dir, 
                                 svm_segment_register_t **seg, 
                                 unsigned int *asize)
 {
@@ -1141,8 +1141,7 @@ static void svm_get_prefix_info(struct v
         != MAX_INST_LEN) 
     {
         gdprintk(XENLOG_ERR, "get guest instruction failed\n");
-        domain_crash(current->domain);
-        return;
+        return 0;
     }
 
     for (i = 0; i < MAX_INST_LEN; i++)
@@ -1200,8 +1199,9 @@ static void svm_get_prefix_info(struct v
         default:
             break;
         }
-        return;
-    }
+        break;
+    }
+    return 1;
 }
 
 
@@ -1236,7 +1236,8 @@ static int svm_get_io_address(
         isize --;
 
     if (isize > 1) 
-        svm_get_prefix_info(v, info.fields.type, &seg, &asize);
+        if ( !svm_get_prefix_info(v, info.fields.type, &seg, &asize) )
+            return 0;
 
     if (info.fields.type == IOREQ_WRITE)
     {
@@ -1591,7 +1592,10 @@ static void svm_cr_access(
     enum instruction_index list_b[] = {INSTR_MOVCR2, INSTR_SMSW};
     enum instruction_index match;
 
-    inst_copy_from_guest(buffer, svm_rip2pointer(v), sizeof(buffer));
+    if ( inst_copy_from_guest(buffer, svm_rip2pointer(v), sizeof(buffer))
+         != sizeof buffer )
+        /* #PF will have been delivered if appropriate. */
+        return;
 
     /* get index to first actual instruction byte - as we will need to know 
        where the prefix lives later on */
@@ -1607,6 +1611,9 @@ static void svm_cr_access(
         inst_len = __get_instruction_length_from_list(
             v, list_b, ARRAY_SIZE(list_b), &buffer[index], &match);
     }
+
+    if ( inst_len == 0 )
+        return;
 
     inst_len += index;
 
@@ -1940,7 +1947,7 @@ void svm_handle_invlpg(const short invlp
     if ( inst_copy_from_guest(opcode, svm_rip2pointer(v), length) < length )
     {
         gdprintk(XENLOG_ERR, "Error reading memory %d bytes\n", length);
-        goto crash;
+        return;
     }
 
     if ( invlpga )
@@ -2055,6 +2062,8 @@ asmlinkage void svm_vmexit_handler(struc
             goto exit_and_crash;
         /* AMD Vol2, 15.11: INT3, INTO, BOUND intercepts do not update RIP. */
         inst_len = __get_instruction_length(v, INSTR_INT3, NULL);
+        if ( inst_len == 0 )
+            break;
         __update_guest_eip(regs, inst_len);
         domain_pause_for_debugger();
         break;
@@ -2131,6 +2140,8 @@ asmlinkage void svm_vmexit_handler(struc
 
     case VMEXIT_VMMCALL:
         inst_len = __get_instruction_length(v, INSTR_VMCALL, NULL);
+        if ( inst_len == 0 ) 
+            break;
         HVMTRACE_1D(VMMCALL, v, regs->eax);
         rc = hvm_do_hypercall(regs);
         if ( rc != HVM_HCALL_preempted )

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