[Qemu-devel] a newbie question: code patches

[Qemu-devel] a newbie question: code patches

[cheetah]

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Hi folks,

I need to do some changes to qemu-kvm. However, on the kvm website, it is
suggested to develop against qemu.git. I am wondering if I develop against
qemu.git, because my fix may depend on some new patch that is only in
qemu.git, it seems very hard to generate a patch for the qemu-kvm. But my
goal is to generate a patch to qemu-kvm while contribute the patch to qemu.

Could you give me some advice? Should I develop again qemu.git or
qemu-kvm.git? How to manage the patch generating process less painful?

Thank you very much.

Regards,
Peter

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Re: [Qemu-devel] a newbie question: code patches

[Stefan Hajnoczi]

On Fri, Aug 5, 2011 at 9:56 AM, cheetah <xuwh06@gmail.com> wrote:
> I need to do some changes to qemu-kvm. However, on the kvm website, it is
> suggested to develop against qemu.git. I am wondering if I develop against
> qemu.git, because my fix may depend on some new patch that is only in
> qemu.git, it seems very hard to generate a patch for the qemu-kvm. But my
> goal is to generate a patch to qemu-kvm while contribute the patch to qemu.
> Could you give me some advice? Should I develop again qemu.git or
> qemu-kvm.git? How to manage the patch generating process less painful?

It depends what code you are changing.  If you are changing anything
non-KVM or PCI-passthrough specific, then the number of conflicts when
applying your patches against qemu-kvm.git will be low (or zero).

Which areas of the code are you going to touch?

Stefan

Re: [Qemu-devel] a newbie question: code patches

[cheetah]

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Thanks for the quickly reply.

I am going to change/add the block driver and some image format code. If I
develop against the qemu.git, can I easily generate a patch to apply to
qemu-kvm.git too? Do you have some "best practices" to recommend? ;) Thanks!

Regards,
Peter

On Fri, Aug 5, 2011 at 2:00 AM, Stefan Hajnoczi <stefanha@gmail.com> wrote:

> On Fri, Aug 5, 2011 at 9:56 AM, cheetah <xuwh06@gmail.com> wrote:
> > I need to do some changes to qemu-kvm. However, on the kvm website, it is
> > suggested to develop against qemu.git. I am wondering if I develop
> against
> > qemu.git, because my fix may depend on some new patch that is only in
> > qemu.git, it seems very hard to generate a patch for the qemu-kvm. But my
> > goal is to generate a patch to qemu-kvm while contribute the patch to
> qemu.
> > Could you give me some advice? Should I develop again qemu.git or
> > qemu-kvm.git? How to manage the patch generating process less painful?
>
> It depends what code you are changing.  If you are changing anything
> non-KVM or PCI-passthrough specific, then the number of conflicts when
> applying your patches against qemu-kvm.git will be low (or zero).
>
> Which areas of the code are you going to touch?
>
> Stefan
>

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Re: [Qemu-devel] a newbie question: code patches

[Paolo Bonzini]

On 08/05/2011 11:04 AM, cheetah wrote:
> Thanks for the quickly reply.
>
> I am going to change/add the block driver and some image format code. If
> I develop against the qemu.git, can I easily generate a patch to apply
> to qemu-kvm.git too?

Yes, or vice versa too.  You can develop against qemu-kvm.git if that's 
what you use, and retest with qemu.git before submitting.

Paolo

Re: [Qemu-devel] a newbie question: code patches

[cheetah]

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Sounds great. Thanks.
I am a newbie and still confusing on how to do it. Please excuse my
ignorance.

If I forked a my own branch on qemu.git and develop against it.
For instance I change qcow2.c which depends on some functions in block.c
which are different from qemu-kvm.git because qemu-kvm.git has an old
version of block.c

In this case I need to generate a patch for both qcow2.c and block.c by diff
with the qemu-kvm.git's version. This is done manually. And if more files
are involved, it becomes really painful.

Is there any better way to generate a patch for qemu-kvm.git easily?

Peter

On Fri, Aug 5, 2011 at 2:10 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:

> On 08/05/2011 11:04 AM, cheetah wrote:
>
>> Thanks for the quickly reply.
>>
>> I am going to change/add the block driver and some image format code. If
>> I develop against the qemu.git, can I easily generate a patch to apply
>> to qemu-kvm.git too?
>>
>
> Yes, or vice versa too.  You can develop against qemu-kvm.git if that's
> what you use, and retest with qemu.git before submitting.
>
> Paolo
>

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Re: [Qemu-devel] a newbie question: code patches

[Stefan Hajnoczi]

On Fri, Aug 5, 2011 at 10:19 AM, cheetah <xuwh06@gmail.com> wrote:
> Sounds great. Thanks.
> I am a newbie and still confusing on how to do it. Please excuse my
> ignorance.
> If I forked a my own branch on qemu.git and develop against it.
> For instance I change qcow2.c which depends on some functions in block.c
> which are different from qemu-kvm.git because qemu-kvm.git has an old
> version of block.c
> In this case I need to generate a patch for both qcow2.c and block.c by diff
> with the qemu-kvm.git's version. This is done manually. And if more files
> are involved, it becomes really painful.
> Is there any better way to generate a patch for qemu-kvm.git easily?

The block layer is the same in qemu-kvm.git.  The will be zero or very
few conflicts, so developing against qemu.git is the right thing.  For
performance testing you may wish to git format-patch and apply those
patches to a qemu-kvm.git tree.

Please share what you plan to work on with the community.  This can
save you a lot of time and avoid duplicating work.  Before you post,
check out the "block layer roadmap thread" which lists many of the
proposed changes that have been discussed:
http://lists.gnu.org/archive/html/qemu-devel/2011-07/msg03162.html

If you send an email explaining what you'd like to change you'll get
advice on how to get started.

Stefan

Re: [Qemu-devel] a newbie question: code patches

[cheetah]

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Thanks for the advice.
I will formalize my plan and send to the maillist.

Peter

On Fri, Aug 5, 2011 at 2:33 AM, Stefan Hajnoczi <stefanha@gmail.com> wrote:

> On Fri, Aug 5, 2011 at 10:19 AM, cheetah <xuwh06@gmail.com> wrote:
> > Sounds great. Thanks.
> > I am a newbie and still confusing on how to do it. Please excuse my
> > ignorance.
> > If I forked a my own branch on qemu.git and develop against it.
> > For instance I change qcow2.c which depends on some functions in block.c
> > which are different from qemu-kvm.git because qemu-kvm.git has an old
> > version of block.c
> > In this case I need to generate a patch for both qcow2.c and block.c by
> diff
> > with the qemu-kvm.git's version. This is done manually. And if more files
> > are involved, it becomes really painful.
> > Is there any better way to generate a patch for qemu-kvm.git easily?
>
> The block layer is the same in qemu-kvm.git.  The will be zero or very
> few conflicts, so developing against qemu.git is the right thing.  For
> performance testing you may wish to git format-patch and apply those
> patches to a qemu-kvm.git tree.
>
> Please share what you plan to work on with the community.  This can
> save you a lot of time and avoid duplicating work.  Before you post,
> check out the "block layer roadmap thread" which lists many of the
> proposed changes that have been discussed:
> http://lists.gnu.org/archive/html/qemu-devel/2011-07/msg03162.html
>
> If you send an email explaining what you'd like to change you'll get
> advice on how to get started.
>
> Stefan
>

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