From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <JBeulich@suse.com>
Subject: Re: [PATCH RFC V7 1/5] xen: Emulate with no writes
Date: Tue, 26 Aug 2014 14:56:56 +0100
Message-ID: <53FCAE48020000780002DA36@mail.emea.novell.com>
References: <1407943689-9249-1-git-send-email-rcojocaru@bitdefender.com>
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To: Razvan Cojocaru <rcojocaru@bitdefender.com>
Cc: kevin.tian@intel.com, ian.campbell@citrix.com, stefano.stabellini@eu.citrix.com, andrew.cooper3@citrix.com, eddie.dong@intel.com, xen-devel@lists.xen.org, jun.nakajima@intel.com, ian.jackson@eu.citrix.com
List-Id: xen-devel@lists.xenproject.org

>>> On 13.08.14 at 17:28, <rcojocaru@bitdefender.com> wrote:
> +void hvm_emulate_one_full(bool_t nowrite, unsigned int trapnr,
> +    unsigned int errcode)
> +{
> +    struct hvm_emulate_ctxt ctx = {{ 0 }};
> +    int rc;
> +
> +    hvm_emulate_prepare(&ctx, guest_cpu_user_regs());
> +
> +    if ( nowrite )
> +        rc = hvm_emulate_one_no_write(&ctx);
> +    else
> +        rc = hvm_emulate_one(&ctx);
> +
> +    switch ( rc )
> +    {
> +    case X86EMUL_UNHANDLEABLE:
> +        gdprintk(XENLOG_DEBUG, "Emulation failed @ %04x:%lx: "
> +               "%02x %02x %02x %02x %02x %02x %02x %02x %02x %02x\n",
> +               hvmemul_get_seg_reg(x86_seg_cs, &ctx)->sel,
> +               ctx.insn_buf_eip,
> +               ctx.insn_buf[0], ctx.insn_buf[1],
> +               ctx.insn_buf[2], ctx.insn_buf[3],
> +               ctx.insn_buf[4], ctx.insn_buf[5],
> +               ctx.insn_buf[6], ctx.insn_buf[7],
> +               ctx.insn_buf[8], ctx.insn_buf[9]);
> +        hvm_inject_hw_exception(trapnr, errcode);
> +        break;
> +    case X86EMUL_EXCEPTION:
> +        if ( ctx.exn_pending )
> +            hvm_inject_hw_exception(ctx.exn_vector, ctx.exn_error_code);
> +        break;

Shouldn't you act on X86EMUL_RETRY here? Or at least not fall through
to the writeback below?

Jan