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

[Kai Huang <kai.huang@xxxxxxxxxxxxxxx>]

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
> ~Andrew
>
> > +
> >   ### gdb
> >   > `= <baud>[/<clock_hz>][,DPS[,<io-base>[,<irq>[,<port-bdf>[,<bridge-bdf>]]]] 
> > | pci | amt ] `
> >   
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