Re: [Xen-devel] [PATCH v2 2/3] x86/svm: Improve diagnostics when svm_get_insn_len() fails

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx]
> Sent: 13 December 2018 20:23
> To: Xen-devel <xen-devel@xxxxxxxxxxxxx>
> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Jan Beulich
> <JBeulich@xxxxxxxx>; Wei Liu <wei.liu2@xxxxxxxxxx>; Roger Pau Monne
> <roger.pau@xxxxxxxxxx>; Paul Durrant <Paul.Durrant@xxxxxxxxxx>; Boris
> Ostrovsky <boris.ostrovsky@xxxxxxxxxx>; Suravee Suthikulpanit
> <suravee.suthikulpanit@xxxxxxx>; Brian Woods <brian.woods@xxxxxxx>
> Subject: [PATCH v2 2/3] 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.
> 
> 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>

> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Wei Liu <wei.liu2@xxxxxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Paul Durrant <paul.durrant@xxxxxxxxxx>
> CC: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> CC: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
> CC: Brian Woods <brian.woods@xxxxxxx>
> 
> v2:
>  * Drop anonymous union
>  * Rebase
> ---
>  xen/arch/x86/hvm/svm/emulate.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/arch/x86/hvm/svm/emulate.c
> b/xen/arch/x86/hvm/svm/emulate.c
> index 3f695b9..73cef5b 100644
> --- a/xen/arch/x86/hvm/svm/emulate.c
> +++ b/xen/arch/x86/hvm/svm/emulate.c
> @@ -143,8 +143,17 @@ int svm_get_insn_len(struct vcpu *v, enum
> instruction_index insn)
>      }
> 
>      gdprintk(XENLOG_WARNING,
> -             "%s: Mismatch between expected and actual instruction: "
> -             "eip = %lx\n",  __func__, (unsigned long)vmcb->rip);
> +             "%s: Mismatch between expected and actual instruction:\n",
> +             __func__);
> +    gdprintk(XENLOG_WARNING,
> +             "  insn_index %d, opcode %#x modrm %#x\n",
> +             insn, opc_tab[insn].opcode, ((opc_tab[insn].modrm.rm  << 6)
> |
> +                                          (opc_tab[insn].modrm.reg << 3)
> |
> +                                          (opc_tab[insn].modrm.mod)));
> +    gdprintk(XENLOG_WARNING, "  rip %#lx, nextrip %#lx, len %lu\n",
> +             vmcb->rip, vmcb->nextrip, vmcb->nextrip - vmcb->rip);
> +    hvm_dump_emulation_state(XENLOG_G_WARNING, "SVM Insn len",
> +                             &ctxt, X86EMUL_UNHANDLEABLE);
> 
>   out:
>      hvm_inject_hw_exception(TRAP_gp_fault, 0);
> --
> 2.1.4

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