On Tue, Apr 12, 2022 at 12:39:32AM +0530, Faiyaz Mohammed wrote:
> This 'commit 86588296acbf ("fdt: Properly handle "no-map" field in the
> memory region")' is keeping the no-map regions in memblock.memory with
> MEMBLOCK_NOMAP flag set to use no-map memory for EFI using memblock api's,
> but during the initialization sparse_init mark all memblock.memory as
> present using for_each_mem_pfn_range, which is creating the memmap for
> no-map memblock regions. To avoid it skiping the memblock.memory regions
> set with MEMBLOCK_NOMAP set and with this change we will be able to save
> ~11MB memory for ~612MB carve out.
The MEMBLOCK_NOMAP is very fragile and caused a lot of issues already. I
really don't like the idea if adding more implicit assumptions about how
NOMAP memory may or may not be used in a generic iterator function.
--
Sincerely yours,
Mike.
On 4/12/2022 10:56 PM, Mike Rapoport wrote:
> On Tue, Apr 12, 2022 at 12:39:32AM +0530, Faiyaz Mohammed wrote:
>> This 'commit 86588296acbf ("fdt: Properly handle "no-map" field in the
>> memory region")' is keeping the no-map regions in memblock.memory with
>> MEMBLOCK_NOMAP flag set to use no-map memory for EFI using memblock api's,
>> but during the initialization sparse_init mark all memblock.memory as
>> present using for_each_mem_pfn_range, which is creating the memmap for
>> no-map memblock regions. To avoid it skiping the memblock.memory regions
>> set with MEMBLOCK_NOMAP set and with this change we will be able to save
>> ~11MB memory for ~612MB carve out.
> The MEMBLOCK_NOMAP is very fragile and caused a lot of issues already. I
> really don't like the idea if adding more implicit assumptions about how
> NOMAP memory may or may not be used in a generic iterator function.
Sorry for delayed response.
Yes, it is possible that implicit assumption can create
misunderstanding. How about adding command line option and control the
no-map region in fdt.c driver, to decide whether to keep "no-map" region
with NOMAP flag or remove?. Something like below
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -1180,8 +1180,10 @@ int __init __weak
early_init_dt_reserve_memory_arch(phys_addr_t base,
*/
if (memblock_is_region_reserved(base, size))
return -EBUSY;
-
- return memblock_mark_nomap(base, size);
+ if (remove_nomap_region)
+ return memblock_remove(base, size);
+ else
+ return memblock_mark_nomap(base, size);
Thanks and regards,
Mohammed Faiyaz
On Thu, May 5, 2022 at 10:17 AM Faiyaz Mohammed
<[email protected]> wrote:
>
>
> On 4/12/2022 10:56 PM, Mike Rapoport wrote:
> > On Tue, Apr 12, 2022 at 12:39:32AM +0530, Faiyaz Mohammed wrote:
> >> This 'commit 86588296acbf ("fdt: Properly handle "no-map" field in the
> >> memory region")' is keeping the no-map regions in memblock.memory with
> >> MEMBLOCK_NOMAP flag set to use no-map memory for EFI using memblock api's,
> >> but during the initialization sparse_init mark all memblock.memory as
> >> present using for_each_mem_pfn_range, which is creating the memmap for
> >> no-map memblock regions. To avoid it skiping the memblock.memory regions
> >> set with MEMBLOCK_NOMAP set and with this change we will be able to save
> >> ~11MB memory for ~612MB carve out.
> > The MEMBLOCK_NOMAP is very fragile and caused a lot of issues already. I
> > really don't like the idea if adding more implicit assumptions about how
> > NOMAP memory may or may not be used in a generic iterator function.
>
> Sorry for delayed response.
> Yes, it is possible that implicit assumption can create
> misunderstanding. How about adding command line option and control the
> no-map region in fdt.c driver, to decide whether to keep "no-map" region
> with NOMAP flag or remove?. Something like below
No. That just added another dimension to the test matrix. Having
things from multiple sources is always a mess.
>
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -1180,8 +1180,10 @@ int __init __weak
> early_init_dt_reserve_memory_arch(phys_addr_t base,
> */
> if (memblock_is_region_reserved(base, size))
> return -EBUSY;
> -
> - return memblock_mark_nomap(base, size);
> + if (remove_nomap_region)
> + return memblock_remove(base, size);
> + else
> + return memblock_mark_nomap(base, size);
> Thanks and regards,
> Mohammed Faiyaz
>