[Xen-changelog] [xen staging] x86/svm: Improve diagnostics when svm_get_insn_len() fails

[patchbot@xxxxxxx]

commit b58ddf5ed9deca528fadc4befd07b21b98e040a4
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri Nov 30 13:50:54 2018 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Feb 1 11:25:32 2019 +0000

    x86/svm: Improve diagnostics when svm_get_insn_len() fails
    
    Sadly, a lone:
    
      (XEN) emulate.c:156:d2v0 svm_get_insn_len: Mismatch between expected and 
actual instruction: eip = fffff804564139c0
    
    on the console is of no use trying to identify what went wrong.  Dump as 
much
    state as we can to help identify what went wrong.
    
      (XEN) Insn mismatch: Expected opcode 0xf0031, modrm 0, got nrip_len 3, 
emul_len 3
      (XEN) SVM Insn len emulation failed (1): d1v0 64bit @ 0008:0010475f -> 0f 
01 f9 0f 31 5b 31 ff 31 c0 e9 c2 db ff ff 00
    
    Drop the debug-only early exit if the sources of length disagree, because 
the
    only effect it has it to avoid the more detailed analysis of what went 
wrong.
    
    Reported-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Brian Woods <brian.woods@xxxxxxx>
    Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
    Release-acked-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/arch/x86/hvm/svm/emulate.c | 19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/xen/arch/x86/hvm/svm/emulate.c b/xen/arch/x86/hvm/svm/emulate.c
index e01402210a..3e52592847 100644
--- a/xen/arch/x86/hvm/svm/emulate.c
+++ b/xen/arch/x86/hvm/svm/emulate.c
@@ -64,7 +64,6 @@ static unsigned long svm_nextrip_insn_length(struct vcpu *v)
  */
 unsigned int svm_get_insn_len(struct vcpu *v, unsigned int instr_enc)
 {
-    struct vmcb_struct *vmcb = v->arch.hvm.svm.vmcb;
     struct hvm_emulate_ctxt ctxt;
     struct x86_emulate_state *state;
     unsigned long nrip_len, emul_len;
@@ -92,15 +91,6 @@ unsigned int svm_get_insn_len(struct vcpu *v, unsigned int 
instr_enc)
     modrm_mod = x86_insn_modrm(state, &modrm_rm, &modrm_reg);
     x86_emulate_free_state(state);
 
-#ifndef NDEBUG
-    if ( nrip_len && nrip_len != emul_len )
-    {
-        gprintk(XENLOG_WARNING, "insn-len[%02x]=%lu (exp %lu)\n",
-                ctxt.ctxt.opcode, nrip_len, emul_len);
-        return nrip_len;
-    }
-#endif
-
     /* Extract components from instr_enc. */
     instr_modrm  = instr_enc & 0xff;
     instr_opcode = instr_enc >> 8;
@@ -116,9 +106,12 @@ unsigned int svm_get_insn_len(struct vcpu *v, unsigned int 
instr_enc)
             return emul_len;
     }
 
-    gdprintk(XENLOG_WARNING,
-             "%s: Mismatch between expected and actual instruction: "
-             "eip = %lx\n",  __func__, (unsigned long)vmcb->rip);
+    printk(XENLOG_G_WARNING
+           "Insn mismatch: Expected opcode %#x, modrm %#x, got nrip_len %lu, 
emul_len %lu\n",
+           instr_opcode, instr_modrm, nrip_len, emul_len);
+    hvm_dump_emulation_state(XENLOG_G_WARNING, "SVM Insn len",
+                             &ctxt, X86EMUL_UNHANDLEABLE);
+
     hvm_inject_hw_exception(TRAP_gp_fault, 0);
     return 0;
 }
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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