diff mbox series

[v2,1/1] of: fdt: Scan /memreserve/ last

Message ID 20230410120017.41664-2-tanure@linux.com
State New
Headers
Series Fix Random Kernel panic from when fail to reserve memory |

Commit Message

Lucas Tanure April 10, 2023, noon UTC 
  Change the order of scanning /memreserve/ and /reserved-memory node.
/reserved-memory node should go first, as it has a more updated
description of the memory regions and it can apply flags, like nomap.
Also, /memreserve/ should avoid reserving regions described in
/reserved-memory node.

Signed-off-by: Lucas Tanure <tanure@linux.com>
---
 drivers/of/fdt.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

Comments

Rob Herring April 10, 2023, 12:52 p.m. UTC | #1 
On Mon, Apr 10, 2023 at 7:00 AM Lucas Tanure <tanure@linux.com> wrote:
>
> Change the order of scanning /memreserve/ and /reserved-memory node.
> /reserved-memory node should go first, as it has a more updated
> description of the memory regions and it can apply flags, like nomap.
> Also, /memreserve/ should avoid reserving regions described in
> /reserved-memory node.

Like I said on v1, I think doing this has a high chance of causing
regressions on other platforms. It should probably not go to stable
for some time after a kernel release.

> Signed-off-by: Lucas Tanure <tanure@linux.com>
> ---
>  drivers/of/fdt.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index d1a68b6d03b3..26e608d8025d 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -635,16 +635,21 @@ void __init early_init_fdt_scan_reserved_mem(void)
>         if (!initial_boot_params)
>                 return;
>
> +       fdt_scan_reserved_mem();
> +       fdt_reserve_elfcorehdr();
> +
>         /* Process header /memreserve/ fields */
>         for (n = 0; ; n++) {
>                 fdt_get_mem_rsv(initial_boot_params, n, &base, &size);
>                 if (!size)
>                         break;
> +               if (memblock_overlaps_region(&memblock.memory, base, size) &&
> +                   memblock_is_region_reserved(base, size))

Just to make sure, a partial overlap will still get reserved?

> +                       break;

Shouldn't we continue to the next entry rather than stopping.

> +
>                 memblock_reserve(base, size);
>         }
>
> -       fdt_scan_reserved_mem();
> -       fdt_reserve_elfcorehdr();
>         fdt_init_reserved_mem();
>  }
>
> --
> 2.40.0
>
Lucas Tanure April 10, 2023, 2:58 p.m. UTC | #2 
On Mon, Apr 10, 2023 at 8:52 AM Rob Herring <robh+dt@kernel.org> wrote:
>
> On Mon, Apr 10, 2023 at 7:00 AM Lucas Tanure <tanure@linux.com> wrote:
> >
> > Change the order of scanning /memreserve/ and /reserved-memory node.
> > /reserved-memory node should go first, as it has a more updated
> > description of the memory regions and it can apply flags, like nomap.
> > Also, /memreserve/ should avoid reserving regions described in
> > /reserved-memory node.
>
> Like I said on v1, I think doing this has a high chance of causing
> regressions on other platforms. It should probably not go to stable
> for some time after a kernel release.
>
> > Signed-off-by: Lucas Tanure <tanure@linux.com>
> > ---
> >  drivers/of/fdt.c | 9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> > index d1a68b6d03b3..26e608d8025d 100644
> > --- a/drivers/of/fdt.c
> > +++ b/drivers/of/fdt.c
> > @@ -635,16 +635,21 @@ void __init early_init_fdt_scan_reserved_mem(void)
> >         if (!initial_boot_params)
> >                 return;
> >
> > +       fdt_scan_reserved_mem();
> > +       fdt_reserve_elfcorehdr();
> > +
> >         /* Process header /memreserve/ fields */
> >         for (n = 0; ; n++) {
> >                 fdt_get_mem_rsv(initial_boot_params, n, &base, &size);
> >                 if (!size)
> >                         break;
> > +               if (memblock_overlaps_region(&memblock.memory, base, size) &&
> > +                   memblock_is_region_reserved(base, size))
>
> Just to make sure, a partial overlap will still get reserved?
A partial overlap will get reserved if not already reserved by the
/reserved-memory node.
>
> > +                       break;
>
> Shouldn't we continue to the next entry rather than stopping.
Yes, my mistake; I will send v3.
>
> > +
> >                 memblock_reserve(base, size);
> >         }
> >
> > -       fdt_scan_reserved_mem();
> > -       fdt_reserve_elfcorehdr();
> >         fdt_init_reserved_mem();
> >  }
> >
> > --
> > 2.40.0
> >
Mike Rapoport April 10, 2023, 4:40 p.m. UTC | #3 
On Mon, Apr 10, 2023 at 08:00:17AM -0400, Lucas Tanure wrote:
> Change the order of scanning /memreserve/ and /reserved-memory node.
> /reserved-memory node should go first, as it has a more updated
> description of the memory regions and it can apply flags, like nomap.
> Also, /memreserve/ should avoid reserving regions described in
> /reserved-memory node.
> 
> Signed-off-by: Lucas Tanure <tanure@linux.com>
> ---
>  drivers/of/fdt.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index d1a68b6d03b3..26e608d8025d 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -635,16 +635,21 @@ void __init early_init_fdt_scan_reserved_mem(void)
>  	if (!initial_boot_params)
>  		return;
>  
> +	fdt_scan_reserved_mem();
> +	fdt_reserve_elfcorehdr();
> +
>  	/* Process header /memreserve/ fields */
>  	for (n = 0; ; n++) {
>  		fdt_get_mem_rsv(initial_boot_params, n, &base, &size);
>  		if (!size)
>  			break;
> +		if (memblock_overlaps_region(&memblock.memory, base, size) &&
> +		    memblock_is_region_reserved(base, size))
> +			break;

I don't think this is really needed, it's ok to reserve the same ranges
multiple times.
Both checks are not cheap, so it'll be better to just reserve everything
both from performance and simplicity points of view.

> +
>  		memblock_reserve(base, size);
>  	}
>  
> -	fdt_scan_reserved_mem();
> -	fdt_reserve_elfcorehdr();
>  	fdt_init_reserved_mem();
>  }
>  
> -- 
> 2.40.0
>
diff mbox series

Patch

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index d1a68b6d03b3..26e608d8025d 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -635,16 +635,21 @@  void __init early_init_fdt_scan_reserved_mem(void)
 	if (!initial_boot_params)
 		return;
 
+	fdt_scan_reserved_mem();
+	fdt_reserve_elfcorehdr();
+
 	/* Process header /memreserve/ fields */
 	for (n = 0; ; n++) {
 		fdt_get_mem_rsv(initial_boot_params, n, &base, &size);
 		if (!size)
 			break;
+		if (memblock_overlaps_region(&memblock.memory, base, size) &&
+		    memblock_is_region_reserved(base, size))
+			break;
+
 		memblock_reserve(base, size);
 	}
 
-	fdt_scan_reserved_mem();
-	fdt_reserve_elfcorehdr();
 	fdt_init_reserved_mem();
 }