linux-kernel - Re: [PATCH 2/3] Documentation: kvm: Convert cpuid.txt to .rst

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Date:   Mon, 8 Jul 2019 13:15:10 -0700
From:   Luke Nowakowski-Krijger <lnowakow@....ucsd.edu>
To:     Jonathan Corbet <corbet@....net>
Cc:     linux-kernel-mentees@...ts.linuxfoundation.org,
        pbonzini@...hat.com, rkrcmar@...hat.com, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] Documentation: kvm: Convert cpuid.txt to .rst

On Mon, Jul 08, 2019 at 02:00:22PM -0600, Jonathan Corbet wrote:
> On Sat,  6 Jul 2019 14:38:14 -0700
> Luke Nowakowski-Krijger <lnowakow@....ucsd.edu> wrote:
> 
> > From: Luke Nowakowski-Krijger <lnowakow@....ucsd.edu>
> > 
> > Convert cpuid.txt to .rst format to be parsable by sphinx. 
> > 
> > Change format and spacing to make function definitions and return values
> > much more clear. Also added a table that is parsable by sphinx and makes
> > the information much more clean. 
> > 
> > Signed-off-by: Luke Nowakowski-Krijger <lnowakow@....ucsd.edu>
> > ---
> >  Documentation/virtual/kvm/cpuid.rst | 99 +++++++++++++++++++++++++++++
> >  Documentation/virtual/kvm/cpuid.txt | 83 ------------------------
> >  2 files changed, 99 insertions(+), 83 deletions(-)
> >  create mode 100644 Documentation/virtual/kvm/cpuid.rst
> >  delete mode 100644 Documentation/virtual/kvm/cpuid.txt
> > 
> > diff --git a/Documentation/virtual/kvm/cpuid.rst b/Documentation/virtual/kvm/cpuid.rst
> > new file mode 100644
> > index 000000000000..1a03336a500e
> > --- /dev/null
> > +++ b/Documentation/virtual/kvm/cpuid.rst
> > @@ -0,0 +1,99 @@
> > +.. SPDX-License-Identifier: GPL-2.0
> 
> Do you know that this is the appropriate license for this file?  If so, you
> should say how you know that.  I appreciate that you thought to add the
> SPDX line, but we have to be sure that it actually matches the intent of
> the creator of this file.
> 

I do not know what the authors intent was. You are right. This is not my
work after all. Ill remove it in the next version.

> > +==============
> > +KVM CPUID bits
> > +==============
> > +
> > +:Author: Glauber Costa <glommer@...hat.com>, Red Hat Inc, 2010
> 
> I rather suspect that email address doesn't work these days.
> 

No I guess it wont :). We would still keep this correct? 

> > +A guest running on a kvm host, can check some of its features using
> > +cpuid. This is not always guaranteed to work, since userspace can
> > +mask-out some, or even all KVM-related cpuid features before launching
> > +a guest.
> > +
> > +KVM cpuid functions are:
> > +
> > +function: **KVM_CPUID_SIGNATURE (0x40000000)**
> 
> I wouldn't add the **markup** here, it doesn't really help.
> 

My intent was to make the "function" part more readable immediately
because otherwise it sort of looks like a wall of text. I might have
gotten a little too fancy here though. 

> > +
> > +returns::
> > + 
> > +   eax = 0x40000001
> > +   ebx = 0x4b4d564b
> > +   ecx = 0x564b4d56
> > +   edx = 0x4d
> > +
> > +Note that this value in ebx, ecx and edx corresponds to the string "KVMKVMKVM".
> > +The value in eax corresponds to the maximum cpuid function present in this leaf,
> > +and will be updated if more functions are added in the future.
> > +Note also that old hosts set eax value to 0x0. This should
> > +be interpreted as if the value was 0x40000001.
> > +This function queries the presence of KVM cpuid leafs.
> > +
> > +function: **define KVM_CPUID_FEATURES (0x40000001)**
> > +
> > +returns::
> > +
> > +          ebx, ecx
> > +          eax = an OR'ed group of (1 << flag)
> > +
> > +where ``flag`` is defined as below:
> > +
> > ++--------------------------------+------------+---------------------------------+
> > +| flag                           | value      | meaning                         |
> > ++================================+============+=================================+
> > +| KVM_FEATURE_CLOCKSOURCE        | 0          | kvmclock available at msrs      |
> > +|                                |            | 0x11 and 0x12                   |
> 
> You might consider using the
> 
>     ======= ===== ======
>     simpler table format
>     ======= ===== ======
> 
> here, it might be a bit easier to read and maintain.
>

Understood. 

> Thanks,
> 
> jon

Thanks for the review, 
- Luke