Re: [Xen-devel] [PATCH RFC 7/9] xen: Handle resumed instruction based on previous mem_event reply

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.07.14 at 15:33, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
> In a scenario where a page fault that triggered a mem_event occured,
> p2m_mem_access_check() will now be able to either 1) emulate the
> current instruction, 2) skip the current instruction, or 3) emulate
> it, but don't allow it to perform any writes. Since some SSE2
> instructions are problematic to emulate (Firefox uses some),
> support for setting the A and D (accessed and dirty) bits has been
> added (please see p2m_set_ad_bits()).

Sadly that reference is useless - the function doesn't have any
explanation what all this is about either.

> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -1372,6 +1372,16 @@ void hvm_emulate_one_full(bool_t nowrite)
>      switch ( rc )
>      {
>      case X86EMUL_UNHANDLEABLE:
> +        printk("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(TRAP_invalid_op, HVM_DELIVER_NO_ERROR_CODE);
>          break;

Since this is non-fatal to the guest, this must get its log level lowered.

> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -121,6 +121,9 @@ struct vcpu *alloc_vcpu(
>      v->domain = d;
>      v->vcpu_id = vcpu_id;
>  
> +    v->sse_pg_dirty.eip = 0;
> +    v->sse_pg_dirty.gla = 0;
> +

All fields start out as zero already. And this is hardly arch-independent
code.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel