diff mbox series

[v2,7/9] mm: Calc the right pfn if page size is not 4K

Message ID 20220414101314.1250667-8-mawupeng1@huawei.com
State Accepted
Commit aa282a157bf8ff79bed9164dc5e0e99f0d9e9755
Headers show
Series introduce mirrored memory support for arm64 | expand

Commit Message

mawupeng April 14, 2022, 10:13 a.m. UTC 
From: Ma Wupeng <mawupeng1@huawei.com>

Previous 0x100000 is used to check the 4G limit in
find_zone_movable_pfns_for_nodes(). This is right in x86 because
the page size can only be 4K. But 16K and 64K are available in
arm64. So replace it with PHYS_PFN(SZ_4G).

Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
---
 mm/page_alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

David Hildenbrand April 19, 2022, 9:59 a.m. UTC | #1 
On 14.04.22 12:13, Wupeng Ma wrote:
> From: Ma Wupeng <mawupeng1@huawei.com>
> 
> Previous 0x100000 is used to check the 4G limit in
> find_zone_movable_pfns_for_nodes(). This is right in x86 because
> the page size can only be 4K. But 16K and 64K are available in
> arm64. So replace it with PHYS_PFN(SZ_4G).
> 
> Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
> ---
>  mm/page_alloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 6e5b4488a0c5..570d0ebf98df 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -7870,7 +7870,7 @@ static void __init find_zone_movable_pfns_for_nodes(void)
>  
>  			usable_startpfn = memblock_region_memory_base_pfn(r);
>  
> -			if (usable_startpfn < 0x100000) {
> +			if (usable_startpfn < PHYS_PFN(SZ_4G)) {
>  				mem_below_4gb_not_mirrored = true;
>  				continue;
>  			}

Reviewed-by: David Hildenbrand <david@redhat.com>
Anshuman Khandual April 19, 2022, 11:14 a.m. UTC | #2 
On 4/14/22 15:43, Wupeng Ma wrote:
> From: Ma Wupeng <mawupeng1@huawei.com>
> 
> Previous 0x100000 is used to check the 4G limit in
> find_zone_movable_pfns_for_nodes(). This is right in x86 because
> the page size can only be 4K. But 16K and 64K are available in
> arm64. So replace it with PHYS_PFN(SZ_4G).
> 
> Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
> ---
>  mm/page_alloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 6e5b4488a0c5..570d0ebf98df 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -7870,7 +7870,7 @@ static void __init find_zone_movable_pfns_for_nodes(void)
>  
>  			usable_startpfn = memblock_region_memory_base_pfn(r);
>  
> -			if (usable_startpfn < 0x100000) {
> +			if (usable_startpfn < PHYS_PFN(SZ_4G)) {
>  				mem_below_4gb_not_mirrored = true;
>  				continue;
>  			}

Regardless PFN value should never be encoded directly.

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Ard Biesheuvel April 19, 2022, 6:29 p.m. UTC | #3 
On Tue, 19 Apr 2022 at 13:13, Anshuman Khandual
<anshuman.khandual@arm.com> wrote:
>
>
>
> On 4/14/22 15:43, Wupeng Ma wrote:
> > From: Ma Wupeng <mawupeng1@huawei.com>
> >
> > Previous 0x100000 is used to check the 4G limit in
> > find_zone_movable_pfns_for_nodes(). This is right in x86 because
> > the page size can only be 4K. But 16K and 64K are available in
> > arm64. So replace it with PHYS_PFN(SZ_4G).
> >
> > Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
> > ---
> >  mm/page_alloc.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 6e5b4488a0c5..570d0ebf98df 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -7870,7 +7870,7 @@ static void __init find_zone_movable_pfns_for_nodes(void)
> >
> >                       usable_startpfn = memblock_region_memory_base_pfn(r);
> >
> > -                     if (usable_startpfn < 0x100000) {
> > +                     if (usable_startpfn < PHYS_PFN(SZ_4G)) {
> >                               mem_below_4gb_not_mirrored = true;
> >                               continue;
> >                       }
>
> Regardless PFN value should never be encoded directly.
>
> Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>

Acked-by: Ard Biesheuvel <ardb@kernel.org>

Andrew, can you please take this one through the -mm tree? The rest of
the series needs a bit more work, but is an obvious fix and there is
no point in holding it up.

Thanks,
Ard.
Andrew Morton April 20, 2022, 10:27 p.m. UTC | #4 
On Tue, 19 Apr 2022 20:29:27 +0200 Ard Biesheuvel <ardb@kernel.org> wrote:

> > > --- a/mm/page_alloc.c
> > > +++ b/mm/page_alloc.c
> > > @@ -7870,7 +7870,7 @@ static void __init find_zone_movable_pfns_for_nodes(void)
> > >
> > >                       usable_startpfn = memblock_region_memory_base_pfn(r);
> > >
> > > -                     if (usable_startpfn < 0x100000) {
> > > +                     if (usable_startpfn < PHYS_PFN(SZ_4G)) {
> > >                               mem_below_4gb_not_mirrored = true;
> > >                               continue;
> > >                       }
> >
> > Regardless PFN value should never be encoded directly.
> >
> > Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
> 
> Acked-by: Ard Biesheuvel <ardb@kernel.org>
> 
> Andrew, can you please take this one through the -mm tree? The rest of
> the series needs a bit more work, but is an obvious fix and there is
> no point in holding it up.

Sure.

I'm not seeing any description of the runtime effects of this
shortcoming.  I tentatively queued the fix for 5.18, without a
cc:stable for backporting.  But that might not be the best decision?
Ard Biesheuvel April 20, 2022, 10:39 p.m. UTC | #5 
On Thu, 21 Apr 2022 at 00:27, Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Tue, 19 Apr 2022 20:29:27 +0200 Ard Biesheuvel <ardb@kernel.org> wrote:
>
> > > > --- a/mm/page_alloc.c
> > > > +++ b/mm/page_alloc.c
> > > > @@ -7870,7 +7870,7 @@ static void __init find_zone_movable_pfns_for_nodes(void)
> > > >
> > > >                       usable_startpfn = memblock_region_memory_base_pfn(r);
> > > >
> > > > -                     if (usable_startpfn < 0x100000) {
> > > > +                     if (usable_startpfn < PHYS_PFN(SZ_4G)) {
> > > >                               mem_below_4gb_not_mirrored = true;
> > > >                               continue;
> > > >                       }
> > >
> > > Regardless PFN value should never be encoded directly.
> > >
> > > Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
> >
> > Acked-by: Ard Biesheuvel <ardb@kernel.org>
> >
> > Andrew, can you please take this one through the -mm tree? The rest of
> > the series needs a bit more work, but is an obvious fix and there is
> > no point in holding it up.
>
> Sure.
>
> I'm not seeing any description of the runtime effects of this
> shortcoming.  I tentatively queued the fix for 5.18, without a
> cc:stable for backporting.  But that might not be the best decision?
>

As far as I can tell, mirrored memory is only used on x86 today, where
pages are always 4k.

However, the whole notion of memory below 4 GB being special is a
x86-ism, and so this logic does not appear to extrapolate to other
architectures anyway, and probably needs more work.

So definitely not a backportable fix, but just an incremental
improvement, so either 5.18 or 5.19 should be fine afaict (and no
cc:stable)
diff mbox series

Patch

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6e5b4488a0c5..570d0ebf98df 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7870,7 +7870,7 @@  static void __init find_zone_movable_pfns_for_nodes(void)
 
 			usable_startpfn = memblock_region_memory_base_pfn(r);
 
-			if (usable_startpfn < 0x100000) {
+			if (usable_startpfn < PHYS_PFN(SZ_4G)) {
 				mem_below_4gb_not_mirrored = true;
 				continue;
 			}