linux-kernel - Re: [PATCH] mm/sparse: fix check_usemap_section

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Message-ID: <1620797600.14730.7.camel@mtkswgap22>
Date:   Wed, 12 May 2021 13:33:20 +0800
From:   Miles Chen <miles.chen@...iatek.com>
To:     Mike Rapoport <rppt@...nel.org>
CC:     Andrew Morton <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <wsd_upstream@...iatek.com>
Subject: Re: [PATCH] mm/sparse: fix check_usemap_section_nr warnings

On Tue, 2021-05-11 at 13:24 +0300, Mike Rapoport wrote:
> On Tue, May 11, 2021 at 05:31:14PM +0800, Miles Chen wrote:
> > In current implementation of node_data, if CONFIG_NEED_MULTIPLE_NODES=y,
> > node_data is allocated by kzmalloc. If CONFIG_NEED_MULTIPLE_NODES=n,
> > we use a global variable named "contig_page_data".
> > 
> > If CONFIG_DEBUG_VIRTUAL is not enabled. __pa() can handle both kzalloc and
> > symbol cases. But if CONFIG_DEBUG_VIRTUAL is set, we will have the
> > "virt_to_phys used for non-linear address" warning when booting.
> 
> Maybe we'll just allocate pgdat for CONFIG_NEED_MULTIPLE_NODES=n (which is
> essentially !NUMA) case in, say, free_area_init()?


thanks for your comment.

I check the source tree and found that contig_page_data is used by
crash_core.c as a symbol. I am not familiar with crash_core but I guess
allocate pgdat may break this crash_core users.

For example: some userspace scripts want to read the address of
contig_page_data symbol from a corefile.

kernel/crash_core.c:460:        VMCOREINFO_SYMBOL(contig_page_data);

#ifndef CONFIG_NEED_MULTIPLE_NODES
        VMCOREINFO_SYMBOL(mem_map);
        VMCOREINFO_SYMBOL(contig_page_data);
#endif


Perhaps we should use current simple approach?


>  
> > To fix it, create a small function to handle both translation.
> > 
> > Warning message:
> > [    0.000000] ------------[ cut here ]------------
> > [    0.000000] virt_to_phys used for non-linear address: (____ptrval____) (contig_page_data+0x0/0x1c00)
> > [    0.000000] WARNING: CPU: 0 PID: 0 at arch/arm64/mm/physaddr.c:15 __virt_to_phys+0x58/0x68
> > [    0.000000] Modules linked in:
> > [    0.000000] CPU: 0 PID: 0 Comm: swapper Tainted: G        W         5.13.0-rc1-00074-g1140ab592e2e #3
> > [    0.000000] Hardware name: linux,dummy-virt (DT)
> > [    0.000000] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO BTYPE=--)
> > [    0.000000] pc : __virt_to_phys+0x58/0x68
> > [    0.000000] lr : __virt_to_phys+0x54/0x68
> > [    0.000000] sp : ffff800011833e70
> > [    0.000000] x29: ffff800011833e70 x28: 00000000418a0018 x27: 0000000000000000
> > [    0.000000] x26: 000000000000000a x25: ffff800011b70000 x24: ffff800011b70000
> > [    0.000000] x23: fffffc0001c00000 x22: ffff800011b70000 x21: 0000000047ffffb0
> > [    0.000000] x20: 0000000000000008 x19: ffff800011b082c0 x18: ffffffffffffffff
> > [    0.000000] x17: 0000000000000000 x16: ffff800011833bf9 x15: 0000000000000004
> > [    0.000000] x14: 0000000000000fff x13: ffff80001186a548 x12: 0000000000000000
> > [    0.000000] x11: 0000000000000000 x10: 00000000ffffffff x9 : 0000000000000000
> > [    0.000000] x8 : ffff8000115c9000 x7 : 737520737968705f x6 : ffff800011b62ef8
> > [    0.000000] x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000
> > [    0.000000] x2 : 0000000000000000 x1 : ffff80001159585e x0 : 0000000000000058
> > [    0.000000] Call trace:
> > [    0.000000]  __virt_to_phys+0x58/0x68
> > [    0.000000]  check_usemap_section_nr+0x50/0xfc
> > [    0.000000]  sparse_init_nid+0x1ac/0x28c
> > [    0.000000]  sparse_init+0x1c4/0x1e0
> > [    0.000000]  bootmem_init+0x60/0x90
> > [    0.000000]  setup_arch+0x184/0x1f0
> > [    0.000000]  start_kernel+0x78/0x488
> > [    0.000000] ---[ end trace f68728a0d3053b60 ]---
> > 
> > Signed-off-by: Miles Chen <miles.chen@...iatek.com>
> > ---
> >  mm/sparse.c | 13 +++++++++++--
> >  1 file changed, 11 insertions(+), 2 deletions(-)
> > 
> > diff --git a/mm/sparse.c b/mm/sparse.c
> > index b2ada9dc00cb..55c18aff3e42 100644
> > --- a/mm/sparse.c
> > +++ b/mm/sparse.c
> > @@ -344,6 +344,15 @@ size_t mem_section_usage_size(void)
> >  	return sizeof(struct mem_section_usage) + usemap_size();
> >  }
> >  
> > +static inline phys_addr_t pgdat_to_phys(struct pglist_data *pgdat)
> > +{
> > +#ifndef CONFIG_NEED_MULTIPLE_NODES
> > +	return __pa_symbol(pgdat);
> > +#else
> > +	return __pa(pgdat);
> > +#endif
> > +}
> > +
> >  #ifdef CONFIG_MEMORY_HOTREMOVE
> >  static struct mem_section_usage * __init
> >  sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
> > @@ -362,7 +371,7 @@ sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
> >  	 * from the same section as the pgdat where possible to avoid
> >  	 * this problem.
> >  	 */
> > -	goal = __pa(pgdat) & (PAGE_SECTION_MASK << PAGE_SHIFT);
> > +	goal = pgdat_to_phys(pgdat) & (PAGE_SECTION_MASK << PAGE_SHIFT);
> >  	limit = goal + (1UL << PA_SECTION_SHIFT);
> >  	nid = early_pfn_to_nid(goal >> PAGE_SHIFT);
> >  again:
> > @@ -390,7 +399,7 @@ static void __init check_usemap_section_nr(int nid,
> >  	}
> >  
> >  	usemap_snr = pfn_to_section_nr(__pa(usage) >> PAGE_SHIFT);
> > -	pgdat_snr = pfn_to_section_nr(__pa(pgdat) >> PAGE_SHIFT);
> > +	pgdat_snr = pfn_to_section_nr(pgdat_to_phys(pgdat) >> PAGE_SHIFT);
> >  	if (usemap_snr == pgdat_snr)
> >  		return;
> >  
> > -- 
> > 2.18.0
>