Re: [PATCH 3/3] tools: introduce parameter max_ranges.

[Wei Liu <wei.liu2@citrix.com>]

On Tue, Jan 19, 2016 at 05:27:58PM +0800, Yu Zhang wrote:
> A new parameter - max_ranges is added to set the upper limit of ranges
> to be tracked inside one ioreq server rangeset.
> 
> Ioreq server uses a group of rangesets to track the I/O or memory
> resources to be emulated. The default value of this limit is set to
> 256. Yet there are circumstances under which the limit should exceed
> the default one. E.g. in XenGT, when tracking the per-process graphic
> translation tables on intel broadwell platforms, the number of page
> tables concerned will be several thousand(normally in this case, 8192
> could be a big enough value). Users who set his item explicitly are
> supposed to know the specific scenarios that necessitate this
> configuration.
> 
> Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
> ---
>  docs/man/xl.cfg.pod.5           | 17 +++++++++++++++++
>  tools/libxl/libxl_dom.c         |  3 +++
>  tools/libxl/libxl_types.idl     |  1 +
>  tools/libxl/xl_cmdimpl.c        |  4 ++++
>  xen/arch/x86/hvm/hvm.c          |  7 ++++++-
>  xen/include/public/hvm/params.h |  5 ++++-
>  6 files changed, 35 insertions(+), 2 deletions(-)
> 
> diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
> index 8899f75..562563d 100644
> --- a/docs/man/xl.cfg.pod.5
> +++ b/docs/man/xl.cfg.pod.5
> @@ -962,6 +962,23 @@ FIFO-based event channel ABI support up to 131,071 event channels.
>  Other guests are limited to 4095 (64-bit x86 and ARM) or 1023 (32-bit
>  x86).
>  
> +=item B<max_ranges=N>
> +

This name is too generic. I don't have better suggestion though.

> +Limit the maximum ranges that can be tracked inside one ioreq server
> +rangeset.
> +
> +Ioreq server uses a group of rangesets to track the I/O or memory
> +resources to be emulated. By default, this item is not set. Not
> +configuring this item, or setting its value to 0 will result in the
> +upper limit set to its default value - 256. Yet there are circumstances

No need to say 256 because this might change in the future in
hypervisor.

> +under which the upper limit inside one rangeset should exceed the
> +default one. E.g. in XenGT, when tracking the per-process graphic
> +translation tables on intel broadwell platforms, the number of page
> +tables concerned will be several thousand(normally in this case, 8192
> +could be a big enough value). Users who set his item explicitly are
> +supposed to know the specific scenarios that necessitate this
> +configuration.
> +
>  =back
>  
>  =head2 Paravirtualised (PV) Guest Specific Options
> diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
> index 47971a9..607b0c4 100644
> --- a/tools/libxl/libxl_dom.c
> +++ b/tools/libxl/libxl_dom.c
> @@ -288,6 +288,9 @@ static void hvm_set_conf_params(xc_interface *handle, uint32_t domid,
>                      libxl_defbool_val(info->u.hvm.nested_hvm));
>      xc_hvm_param_set(handle, domid, HVM_PARAM_ALTP2M,
>                      libxl_defbool_val(info->u.hvm.altp2m));
> +    if (info->u.hvm.max_ranges > 0)
> +        xc_hvm_param_set(handle, domid, HVM_PARAM_MAX_RANGES,
> +                        info->u.hvm.max_ranges);
>  }
>  
>  int libxl__build_pre(libxl__gc *gc, uint32_t domid,
> diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
> index 9ad7eba..c936265 100644
> --- a/tools/libxl/libxl_types.idl
> +++ b/tools/libxl/libxl_types.idl
> @@ -518,6 +518,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
>                                         ("serial_list",      libxl_string_list),
>                                         ("rdm", libxl_rdm_reserve),
>                                         ("rdm_mem_boundary_memkb", MemKB),
> +                                       ("max_ranges", uint32),

This also needs a better name.

Another thing is that you need to define LIBXL_HAVE_XXX in libxl.h to
indicate we introduce a new field.

Wei.