Re: [Xen-devel] [v2 02/11] doc: add description for new PML boot parameter

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 16/04/15 05:47, Kai Huang wrote:
>
>
> On 04/15/2015 06:15 PM, Andrew Cooper wrote:
>> On 15/04/15 08:03, Kai Huang wrote:
>>> This patch adds doc description for new boot parameter 'ept=pml'.
>>>
>>> Signed-off-by: Kai Huang <kai.huang@xxxxxxxxxxxxxxx>
>> Personally, I would fold this patch into the previous so the
>> documentation is in the same patch as introduces the parameter.
> Thanks for suggestion. Will do in the next version.
>
>>
>>> ---
>>>   docs/misc/xen-command-line.markdown | 14 ++++++++++++++
>>>   1 file changed, 14 insertions(+)
>>>
>>> diff --git a/docs/misc/xen-command-line.markdown
>>> b/docs/misc/xen-command-line.markdown
>>> index 1dda1f0..ae30d02 100644
>>> --- a/docs/misc/xen-command-line.markdown
>>> +++ b/docs/misc/xen-command-line.markdown
>>> @@ -685,6 +685,20 @@ requirement can be relaxed.  This option is
>>> particularly useful for nested
>>>   virtualization, to allow the L1 hypervisor to use EPT even if the
>>> L0 hypervisor
>>>   does not provide VM\_ENTRY\_LOAD\_GUEST\_PAT.
>>>   +### ept (Intel)
>>> +> `= List of [ pml ]`
>>> +
>>> +> Sub-options:
>>> +
>>> +> `pml`
>>> +
>>> +> This sub-option is boolean type and can be prefixed with `no-` to
>>> effect the
>>> +> inverse meaning.
>>> +
>>> +> Default: `false`
>>> +
>>> +>> Control the use of Page Modification Logging for log-dirty.
>> Can you follow the same style as the "psr" option?  Specifically, I
>> don't think you need to re-describe what a boolean parameter is.
> Thanks for suggestion. I chose to follow the "iommu=" style parameter
> as to me the "ept=" parameter is more likely to the "iommu=" parameter
> -- both of them intend to have various sub-boolean types, within which
> some may or may not be independent to each other.
>
> Referring to 'psr' parameter, does below change look good to you?
>
> +### ept (Intel)
> +> `= List of ( pml<boolean> )`
> +
> +> Default: `false`
> +
> +Controls EPT related features. Currently only Page Modification
> Logging (PML) is
> +the controllable feature as boolean type.
> +
> +PML is a new hardware feature in Intel's Broadwell Server and further
> platforms
> +which reduces hypervisor overhead of log-dirty mechanism by
> automatically
> +recording GPAs (guest physical addresses) when guest memory gets
> dirty, and
> +therefore significantly reducing number of EPT violation caused by write
> +protection of guest memory, which is a necessity to implement log-dirty
> +mechanism before PML.
>
> Thanks,
> -Kai

Yep - that looks good.

~Andrew

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