linux-kernel - Re: [PATCH v3 2/9] kexec_file: Generalize kexec_add

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Date:	Thu, 30 Jun 2016 12:49:44 -0300
From:	Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
To:	Dave Young <dyoung@...hat.com>
Cc:	kexec@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org,
	Eric Biederman <ebiederm@...ssion.com>
Subject: Re: [PATCH v3 2/9] kexec_file: Generalize kexec_add_buffer.

Am Donnerstag, 30 Juni 2016, 11:07:00 schrieb Dave Young:
> On 06/29/16 at 06:18pm, Thiago Jung Bauermann wrote:
> > Am Mittwoch, 29 Juni 2016, 15:47:51 schrieb Dave Young:
> > > On 06/28/16 at 07:18pm, Thiago Jung Bauermann wrote:
> > > > +/**
> > > > + * struct kexec_buf - parameters for finding a place for a buffer
> > > > in
> > > > memory + * @image:   kexec image in which memory to search.
> > > > + * @mem:     On return will have address of the buffer in memory.
> > > > + * @memsz:   Size for the buffer in memory.
> > > > + * @buf_align:       Minimum alignment needed.
> > > > + * @buf_min: The buffer can't be placed below this address.
> > > > + * @buf_max: The buffer can't be placed above this address.
> > > > + * @top_down:        Allocate from top of memory.
> > > > + */
> > > > +struct kexec_buf {
> > > > +     struct kimage *image;
> > > > +     unsigned long mem;
> > > > +     unsigned long memsz;
> > > > +     unsigned long buf_align;
> > > > +     unsigned long buf_min;
> > > > +     unsigned long buf_max;
> > > > +     bool top_down;
> > > > +};
> > > 
> > > Rethink about the first patch, you dropped the user buffer in
> > > kexec_buf
> > > But later your passing IMA digests buffer patchset may need use it.
> > > 
> > > So keep it in kexec_buf should be better.
> > 
> > I'm not following. The IMA buffer patchset doesn't use
> > kexec_locate_mem_hole nor struct kexec_buf.
> 
> It does not use kexec_locate_mem_hole, but the buffer being passed is
> very similar to a kexec_buf struct, no?

If what you're saying is that the arguments passed to 
kexec_add_handover_buffer in the IMA buffer patchset are very similar to the 
arguments passed to kexec_add_buffer then yes, it's true.

> So you may refactor kexec_add_buffer and your new function to pass only
> kimage and a kbuf, it will be better than passing all those arguments
> separately.

To be honest I think struct kexec_buf is an implementation detail inside 
kexec_locate_mem_hole, made necessary because the callback functions it uses 
need to access its arguments. Callers of kexec_locate_mem_hole, 
kexec_add_handover_buffer and kexec_add_buffer shouldn't need to know it 
exists.

[]'s
Thiago Jung Bauermann
IBM Linux Technology Center