linux-kernel - Re: Is: axe read_tscp pvops call. Was: Re: [RFC] ACPI S3 and Xen (suprisingly small\!).

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Message-ID: <20121017165452.GA22740@phenom.dumpdata.com>
Date:	Wed, 17 Oct 2012 12:54:52 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
	lenb@...nel.org, linux-acpi@...r.kernel.org, x86@...nel.org
Subject: Re: Is: axe read_tscp pvops call. Was: Re: [RFC] ACPI S3 and Xen
 (suprisingly small\!).

On Wed, Oct 17, 2012 at 09:50:11AM -0700, H. Peter Anvin wrote:
> On 10/17/2012 09:10 AM, Konrad Rzeszutek Wilk wrote:
> >On Wed, Oct 17, 2012 at 09:03:12AM -0700, H. Peter Anvin wrote:
> >>On 10/17/2012 06:49 AM, Konrad Rzeszutek Wilk wrote:
> >>>
> >>>Note: These are the other patches that went in 3.7-rc1:
> >>>xen/bootup: allow {read|write}_cr8 pvops call [https://lkml.org/lkml/2012/10/10/339]
> >>>xen/bootup: allow read_tscp call for Xen PV guests. [https://lkml.org/lkml/2012/10/10/340]
> >>>
> >>
> >>So WTF do we have a read_tscp PV call?  Again, if there isn't a user
> >>we should just axe it...
> >
> >Let me spin off a patch to see if that can be done.
> >
> 
> Could you do an audit for other pvops calls that have no users?  If
> the *only* user is lguest, we should talk about it, too...

I can do that - but I don't want to be hasty here. There is a bit of
danger here - for example the read_pmc (or read_tsc) is not in use right
now. But it might be when one starts looking at making perf be able to
analyze the hypervisor (hand-waving the implementation details). So while
removing read_pmc now sounds good, it might be needed in the future.

Or maybe not :-)

Let me do a candidate list and get some conversation going.
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