linux-kernel - Re: [PATCH] openrisc: Reserve memblock for initrd

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Date:   Thu, 3 Sep 2020 23:31:35 +0900
From:   Stafford Horne <shorne@...il.com>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        openrisc@...ts.librecores.org
Subject: Re: [PATCH] openrisc: Reserve memblock for initrd

On Tue, Sep 01, 2020 at 03:11:30PM +0300, Mike Rapoport wrote:
> On Tue, Sep 01, 2020 at 07:20:44PM +0900, Stafford Horne wrote:
> > On Tue, Sep 01, 2020 at 08:59:24AM +0300, Mike Rapoport wrote:
> > > On Tue, Sep 01, 2020 at 06:21:01AM +0900, Stafford Horne wrote:
> > > > Recently OpenRISC added support for external initrd images, but I found
> > > > some instability when using larger buildroot initrd images. It turned
> > > > out that I forgot to reserve the memblock space for the initrd image.
> > > > 
> > > > This patch fixes the instability issue by reserving memblock space.
> > > > 
> > > > Fixes: ff6c923dbec3 ("openrisc: Add support for external initrd images")
> > > > Signed-off-by: Stafford Horne <shorne@...il.com>
> > > > ---
> > > >  arch/openrisc/kernel/setup.c | 9 +++++++++
> > > >  1 file changed, 9 insertions(+)
> > > > 
> > > > diff --git a/arch/openrisc/kernel/setup.c b/arch/openrisc/kernel/setup.c
> > > > index b18e775f8be3..2c8aa53cc7ba 100644
> > > > --- a/arch/openrisc/kernel/setup.c
> > > > +++ b/arch/openrisc/kernel/setup.c
> > > > @@ -80,6 +80,15 @@ static void __init setup_memory(void)
> > > >  	 */
> > > >  	memblock_reserve(__pa(_stext), _end - _stext);
> > > >  
> > > > +#ifdef CONFIG_BLK_DEV_INITRD
> > > > +	/* Then reserve the initrd, if any */
> > > > +	if (initrd_start && (initrd_end > initrd_start)) {
> > > > + 	memblock_reserve(ALIGN_DOWN(__pa(initrd_start), PAGE_SIZE),
> > > > +		ALIGN(initrd_end, PAGE_SIZE) -
> > > > +		ALIGN_DOWN(initrd_start, PAGE_SIZE));
> > > > +	}
> > > 
> > > The core mm takes care of reserving the entrire pages for the memory
> > > reserved with memblock, so it is not necessary to do it here.
> > 
> > Thanks for the pointer
> > 
> > I guess what you mean is it is not required to do the page alignment.
> 
> Right. 
> 
> > I used other architectures as an example and most do the alignment, I
> > think for most architectures this can be pulled out to generic code.
> 
> You are more than welcome :)
> We already have a generic free_initrd_mem(), maybe it's time to have a
> generic reserve_initrd_mem().
> 
> I'm ok with openrisc doing the alignment, but I think using local
> variables would make the core more readable, e.g
> 
> 	if (initd_start && (initrd_end)) {
> 		unsigned long aligned_start = ALIGN_DOWN(initrd_start, PAGE_SIZE);
> 		unsigned long aligned_end = ALIGN(end, PAGE_SIZE);
> 
> 		memblock_reserve(aligned_start, aligned_end);
> 	}
> 
> What do you say?

Well, if the alignment is not needed I rather not do it.  That would make the
code as simple as:

        if (initrd_start && (initrd_end > initrd_start)) {
                memblock_reserve(__pa(initrd_start), initrd_end - initrd_start);
        }

Let me look what is involved in making a reserve_initrd_mem().

-Stafford

> > -Stafford
> > 
> > > > +#endif /* CONFIG_BLK_DEV_INITRD */
> > > > +
> > > >  	early_init_fdt_reserve_self();
> > > >  	early_init_fdt_scan_reserved_mem();
> > > >  
> > > > -- 
> > > > 2.26.2
> > > > 
> > > 
> > > -- 
> > > Sincerely yours,
> > > Mike.
> 
> -- 
> Sincerely yours,
> Mike.