Re: [Xen-devel] [PATCH v2 01/10] x86: add an flag to enable Intel Processor Trace in guest

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 03.07.18 at 12:18, <luwei.kang@xxxxxxxxx> wrote:
>> > --- a/docs/misc/xen-command-line.markdown
>> > +++ b/docs/misc/xen-command-line.markdown
>> > @@ -1215,6 +1215,16 @@ Rather than only mapping RAM pages for IOMMU
>> > accesses for Dom0, with this  option all pages not marked as unusable
>> > in the E820 table will get a mapping  established.
>> >
>> > +### ipt
>> > +> `= guest`
>> > +
>> > +> Default: `off`
>> > +
>> > +This option is use for switch on the Intel Processor Trace feature in
>> > +HVM guest when 'ipt=guest'. By default, this feature is disabled in
>> > +guest. Intel Processor Trace virtualization depend on EPT, so it can
>> > +only enabled in HVM guest at present.
>> > +
>> >  ### irq\_ratelimit (x86)
>> 
>> Did you not notice the (x86) here when re-basing?
> 
> So, the option should be "### ipt (x86)" ?

Yes.

>> > +#ifndef __ASM_X86_HVM_IPT_H_
>> > +#define __ASM_X86_HVM_IPT_H_
>> > +
>> > +#define IPT_MODE_OFF        0
>> > +#define IPT_MODE_GUEST      (1<<0)
>> > +
>> > +extern unsigned int ipt_mode;
>> 
>> At this point I can't see why the variable can't be bool. With the patch 
>> being placed first in the series it is also impossible (without
>> peeking into later patches) to judge whether its __read_mostly attribute is 
>> actually appropriate.
> 
> OK, will change it to bool. About __read_mostly attribute,  I will remove it 
> if not read frequency.

No, the point wasn't to remove it, but whether instead it could be
__initdata.

Jan



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