linux-kernel - Re: [PATCH v3 5/7] kexec_file, ricv: print out debugging message if required

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Date:   Mon, 4 Dec 2023 16:14:45 +0000
From:   Conor Dooley <conor@...nel.org>
To:     Baoquan He <bhe@...hat.com>
Cc:     Conor Dooley <conor.dooley@...rochip.com>,
        linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
        x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
        linux-parisc@...r.kernel.org, akpm@...ux-foundation.org,
        joe@...ches.com, nathan@...nel.org
Subject: Re: [PATCH v3 5/7] kexec_file, ricv: print out debugging message if
 required

On Mon, Dec 04, 2023 at 11:38:05PM +0800, Baoquan He wrote:
> On 12/01/23 at 10:38am, Conor Dooley wrote:
> > On Thu, Nov 30, 2023 at 10:39:53AM +0800, Baoquan He wrote:
> > 
> > $subject has a typo in the arch bit :)
> 
> Indeed, will fix if need report. Thanks for careful checking.
> 
> > 
> > > Replace pr_debug() with the newly added kexec_dprintk() in kexec_file
> > > loading related codes.
> > 
> > Commit messages should be understandable in isolation, but this only
> > explains (part of) what is obvious in the diff. Why is this change
> > being made?
> 
> The purpose has been detailedly described in cover letter and patch 1
> log. Andrew has picked these patches into his tree and grabbed the cover
> letter log into the relevant commit for people's later checking. All
> these seven patches will be present in mainline together. This is common
> way when posting patch series? Please let me know if I misunderstand
> anything.

Each patch having a commit message that explains why a change is being
made is the expectation. It is especially useful to explain the why
here, since it is not just a mechanical conversion of pr_debug()s as the
commit message suggests.

> > 
> > > 
> > > And also remove kexec_image_info() because the content has been printed
> > > out in generic code.
> > > 
> > > Signed-off-by: Baoquan He <bhe@...hat.com>
> > > ---
> > >  arch/riscv/kernel/elf_kexec.c     | 11 ++++++-----
> > >  arch/riscv/kernel/machine_kexec.c | 26 --------------------------
> > >  2 files changed, 6 insertions(+), 31 deletions(-)
> > > 
> > > diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
> > > index e60fbd8660c4..5bd1ec3341fe 100644
> > > --- a/arch/riscv/kernel/elf_kexec.c
> > > +++ b/arch/riscv/kernel/elf_kexec.c
> > > @@ -216,7 +216,6 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
> > >  	if (ret)
> > >  		goto out;
> > >  	kernel_start = image->start;
> > > -	pr_notice("The entry point of kernel at 0x%lx\n", image->start);
> > >  
> > >  	/* Add the kernel binary to the image */
> > >  	ret = riscv_kexec_elf_load(image, &ehdr, &elf_info,
> > > @@ -252,8 +251,8 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
> > >  		image->elf_load_addr = kbuf.mem;
> > >  		image->elf_headers_sz = headers_sz;
> > >  
> > > -		pr_debug("Loaded elf core header at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
> > > -			 image->elf_load_addr, kbuf.bufsz, kbuf.memsz);
> > > +		kexec_dprintk("Loaded elf core header at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
> > > +			      image->elf_load_addr, kbuf.bufsz, kbuf.memsz);
> > >  
> > >  		/* Setup cmdline for kdump kernel case */
> > >  		modified_cmdline = setup_kdump_cmdline(image, cmdline,
> > > @@ -275,6 +274,8 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
> > >  		pr_err("Error loading purgatory ret=%d\n", ret);
> > >  		goto out;
> > >  	}
> > > +	kexec_dprintk("Loaded purgatory at 0x%lx\n", kbuf.mem);
> > > +
> > >  	ret = kexec_purgatory_get_set_symbol(image, "riscv_kernel_entry",
> > >  					     &kernel_start,
> > >  					     sizeof(kernel_start), 0);
> > > @@ -293,7 +294,7 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
> > >  		if (ret)
> > >  			goto out;
> > >  		initrd_pbase = kbuf.mem;
> > 
> > > -		pr_notice("Loaded initrd at 0x%lx\n", initrd_pbase);
> > > +		kexec_dprintk("Loaded initrd at 0x%lx\n", initrd_pbase);
> > 
> > This is not a pr_debug().
> > 
> > >  	}
> > >  
> > >  	/* Add the DTB to the image */
> > > @@ -318,7 +319,7 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
> > >  	}
> > >  	/* Cache the fdt buffer address for memory cleanup */
> > >  	image->arch.fdt = fdt;
> > 
> > > -	pr_notice("Loaded device tree at 0x%lx\n", kbuf.mem);
> > > +	kexec_dprintk("Loaded device tree at 0x%lx\n", kbuf.mem);
> > 
> > Neither is this. Why are they being moved from pr_notice()?
> 
> You are right. 
> 
> While always printing out the loaded location of purgatory and
> device tree doesn't make sense. It will be confusing when users
> see these even when they do normal kexec/kdump loading. It should be
> changed to pr_debug().
> 
> Which way do you suggest?
> 1) change it back to pr_debug(), fix it in another patch;
> 2) keep it as is in the patch;

Personally I think it is fine to change them all in one patch, but the
rationale for converting pr_notice() to your new debug infrastructure
needs to be in the commit message.

Thanks,
Conor.

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