linux-kernel - Re: [PATCH 01/11] kexec_file: allow archs to handle special regions while locating memory hole

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Message-ID: <20200701074659.GA3878@dhcp-128-65.nay.redhat.com>
Date:   Wed, 1 Jul 2020 15:46:59 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Hari Bathini <hbathini@...ux.ibm.com>
Cc:     Petr Tesarik <ptesarik@...e.cz>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Pingfan Liu <piliu@...hat.com>,
        Kexec-ml <kexec@...ts.infradead.org>,
        Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        lkml <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...abs.org>,
        Sourabh Jain <sourabhjain@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vivek Goyal <vgoyal@...hat.com>,
        Eric Biederman <ebiederm@...ssion.com>
Subject: Re: [PATCH 01/11] kexec_file: allow archs to handle special regions
 while locating memory hole

On 06/29/20 at 05:26pm, Hari Bathini wrote:
> Hi Petr,
> 
> On 29/06/20 5:09 pm, Petr Tesarik wrote:
> > Hi Hari,
> > 
> > is there any good reason to add two more functions with a very similar
> > name to an existing function? AFAICS all you need is a way to call a
> > PPC64-specific function from within kexec_add_buffer (PATCH 4/11), so
> > you could add something like this:
> > 
> > int __weak arch_kexec_locate_mem_hole(struct kexec_buf *kbuf)
> > {
> > 	return 0;
> > }
> > 
> > Call this function from kexec_add_buffer where appropriate and then
> > override it for PPC64 (it roughly corresponds to your
> > kexec_locate_mem_hole_ppc64() from PATCH 4/11).
> > 
> > FWIW it would make it easier for me to follow the resulting code.
> 
> Right, Petr.
> 
> I was trying out a few things before I ended up with what I sent here.
> Bu yeah.. I did realize arch_kexec_locate_mem_hole() would have been better
> after sending out v1. Will take care of that in v2.

Another way is use arch private function to locate mem hole, then set
kbuf->mem, and then call kexec_add_buf, it will skip the common locate
hole function.

But other than that I have some confusion about those excluded ranges.
Replied a question to patch 4.

Thanks
Dave