linux-kernel - Re: [PATCH v4 5/5] x86: implement crashkernel cma reservation

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Message-ID: <aD7w/YfdKMqa7m89@MiWiFi-R3L-srv>
Date: Tue, 3 Jun 2025 20:56:43 +0800
From: Baoquan He <bhe@...hat.com>
To: Jiri Bohac <jbohac@...e.cz>
Cc: Vivek Goyal <vgoyal@...hat.com>, Dave Young <dyoung@...hat.com>,
	kexec@...ts.infradead.org, Philipp Rudo <prudo@...hat.com>,
	Donald Dutile <ddutile@...hat.com>, Pingfan Liu <piliu@...hat.com>,
	Tao Liu <ltao@...hat.com>, linux-kernel@...r.kernel.org,
	David Hildenbrand <dhildenb@...hat.com>,
	Michal Hocko <mhocko@...e.cz>
Subject: Re: [PATCH v4 5/5] x86: implement crashkernel cma reservation

On 06/03/25 at 02:11pm, Jiri Bohac wrote:
> On Tue, Jun 03, 2025 at 07:02:06PM +0800, Baoquan He wrote:
> > On 05/30/25 at 10:31pm, Jiri Bohac wrote:
> > ......snip.. 
> > > @@ -582,7 +582,7 @@ static void __init arch_reserve_crashkernel(void)
> > >  
> > >  	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
> > >  				&crash_size, &crash_base,
> > > -				&low_size, NULL, &high);
> > > +				&low_size, &cma_size, &high);
> > >  	if (ret)
> > >  		return;
> > >  
> > > @@ -592,6 +592,7 @@ static void __init arch_reserve_crashkernel(void)
> > >  	}
> > >  
> > >  	reserve_crashkernel_generic(crash_size, crash_base, low_size, high);
> > > +	reserve_crashkernel_cma(cma_size);
> > 
> > Wondering if ,high|low is still allowed (or needed) when ,cma is specified.
> 
> Probably not needed but it works, totally independent of the
> extra CMA-reserved area.

Allowing it can simplify the current code, while I can't imagine what
cases need people to specify
"crashkernel=xM,high crashkernel=xM,low crashkernel=zM,cma" at one time.

Just personal thought, I haven't think of a strong reason to prevent it
too.

> 
> I saw no reason to artificially prevent it.
> 
> -- 
> Jiri Bohac <jbohac@...e.cz>
> SUSE Labs, Prague, Czechia
>