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[PATCHv3 02/11] arm64: Handle section maps for swapper/idmap

Started by"Suzuki K. Poulose" <suzuki.poulose@arm.com>
First post2015-10-14 13:30 +0200
Last post2015-10-14 17:20 +0200
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  [PATCHv3 02/11] arm64: Handle section maps for swapper/idmap "Suzuki K. Poulose" <suzuki.poulose@arm.com> - 2015-10-14 13:30 +0200
    Re: [PATCHv3 02/11] arm64: Handle section maps for swapper/idmap Mark Rutland <mark.rutland@arm.com> - 2015-10-14 14:10 +0200
      Re: [PATCHv3 02/11] arm64: Handle section maps for swapper/idmap "Suzuki K. Poulose" <Suzuki.Poulose@arm.com> - 2015-10-14 15:30 +0200
        Re: [PATCHv3 02/11] arm64: Handle section maps for swapper/idmap Mark Rutland <mark.rutland@arm.com> - 2015-10-14 17:00 +0200
          Re: [PATCHv3 02/11] arm64: Handle section maps for swapper/idmap "Suzuki K. Poulose" <Suzuki.Poulose@arm.com> - 2015-10-14 17:10 +0200
            Re: [PATCHv3 02/11] arm64: Handle section maps for swapper/idmap Mark Rutland <mark.rutland@arm.com> - 2015-10-14 17:20 +0200

#1246541 — [PATCHv3 02/11] arm64: Handle section maps for swapper/idmap

From"Suzuki K. Poulose" <suzuki.poulose@arm.com>
Date2015-10-14 13:30 +0200
Subject[PATCHv3 02/11] arm64: Handle section maps for swapper/idmap
Message-ID<qjspQ-5qz-15@gated-at.bofh.it>
We use section maps with 4K page size to create the swapper/idmaps.
So far we have used !64K or 4K checks to handle the case where we
use the section maps.
This patch adds a new symbol, ARM64_SWAPPER_USES_SECTION_MAPS, to
handle cases where we use section maps, instead of using the page size
symbols.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
---
 arch/arm64/include/asm/kernel-pgtable.h |   31 ++++++++-----
 arch/arm64/mm/mmu.c                     |   72 ++++++++++++++-----------------
 2 files changed, 52 insertions(+), 51 deletions(-)

diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index 622929d..5876a36 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -19,6 +19,13 @@
 #ifndef __ASM_KERNEL_PGTABLE_H
 #define __ASM_KERNEL_PGTABLE_H
 
+/* With 4K pages, we use section maps. */
+#ifdef CONFIG_ARM64_4K_PAGES
+#define ARM64_SWAPPER_USES_SECTION_MAPS 1
+#else
+#define ARM64_SWAPPER_USES_SECTION_MAPS 0
+#endif
+
 /*
  * The idmap and swapper page tables need some space reserved in the kernel
  * image. Both require pgd, pud (4 levels only) and pmd tables to (section)
@@ -28,26 +35,28 @@
  * could be increased on the fly if system RAM is out of reach for the default
  * VA range, so 3 pages are reserved in all cases.
  */
-#ifdef CONFIG_ARM64_64K_PAGES
-#define SWAPPER_PGTABLE_LEVELS	(CONFIG_PGTABLE_LEVELS)
-#else
+#if ARM64_SWAPPER_USES_SECTION_MAPS
 #define SWAPPER_PGTABLE_LEVELS	(CONFIG_PGTABLE_LEVELS - 1)
+#else
+#define SWAPPER_PGTABLE_LEVELS	(CONFIG_PGTABLE_LEVELS)
 #endif
 
 #define SWAPPER_DIR_SIZE	(SWAPPER_PGTABLE_LEVELS * PAGE_SIZE)
 #define IDMAP_DIR_SIZE		(3 * PAGE_SIZE)
 
 /* Initial memory map size */
-#ifdef CONFIG_ARM64_64K_PAGES
-#define SWAPPER_BLOCK_SHIFT	PAGE_SHIFT
-#define SWAPPER_BLOCK_SIZE	PAGE_SIZE
-#define SWAPPER_TABLE_SHIFT	PMD_SHIFT
-#else
+#if ARM64_SWAPPER_USES_SECTION_MAPS
 #define SWAPPER_BLOCK_SHIFT	SECTION_SHIFT
 #define SWAPPER_BLOCK_SIZE	SECTION_SIZE
 #define SWAPPER_TABLE_SHIFT	PUD_SHIFT
+#else
+#define SWAPPER_BLOCK_SHIFT	PAGE_SHIFT
+#define SWAPPER_BLOCK_SIZE	PAGE_SIZE
+#define SWAPPER_TABLE_SHIFT	PMD_SHIFT
 #endif
 
+/* The size of the initial kernel direct mapping */
+#define SWAPPER_INIT_MAP_SIZE	(_AC(1, UL) << SWAPPER_TABLE_SHIFT)
 
 /*
  * Initial memory map attributes.
@@ -55,10 +64,10 @@
 #define SWAPPER_PTE_FLAGS	PTE_TYPE_PAGE | PTE_AF | PTE_SHARED
 #define SWAPPER_PMD_FLAGS	PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S
 
-#ifdef CONFIG_ARM64_64K_PAGES
-#define SWAPPER_MM_MMUFLAGS	PTE_ATTRINDX(MT_NORMAL) | SWAPPER_PTE_FLAGS
-#else
+#if ARM64_SWAPPER_USES_SECTION_MAPS
 #define SWAPPER_MM_MMUFLAGS	PMD_ATTRINDX(MT_NORMAL) | SWAPPER_PMD_FLAGS
+#else
+#define SWAPPER_MM_MMUFLAGS	PTE_ATTRINDX(MT_NORMAL) | SWAPPER_PTE_FLAGS
 #endif
 
 
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index eed6d52..bc4373a 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -32,6 +32,7 @@
 
 #include <asm/cputype.h>
 #include <asm/fixmap.h>
+#include <asm/kernel-pgtable.h>
 #include <asm/sections.h>
 #include <asm/setup.h>
 #include <asm/sizes.h>
@@ -406,14 +407,11 @@ static void __init map_mem(void)
 	 * memory addressable from the initial direct kernel mapping.
 	 *
 	 * The initial direct kernel mapping, located at swapper_pg_dir, gives
-	 * us PUD_SIZE (4K pages) or PMD_SIZE (64K pages) memory starting from
-	 * PHYS_OFFSET (which must be aligned to 2MB as per
-	 * Documentation/arm64/booting.txt).
+	 * us PUD_SIZE (with SECTION maps, i.e, 4K) or PMD_SIZE (without
+	 * SECTION maps, i.e, 64K pages) memory starting from PHYS_OFFSET
+	 * (which must be aligned to 2MB as per Documentation/arm64/booting.txt).
 	 */
-	if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
-		limit = PHYS_OFFSET + PMD_SIZE;
-	else
-		limit = PHYS_OFFSET + PUD_SIZE;
+	limit = PHYS_OFFSET + SWAPPER_INIT_MAP_SIZE;
 	memblock_set_current_limit(limit);
 
 	/* map all the memory banks */
@@ -424,21 +422,24 @@ static void __init map_mem(void)
 		if (start >= end)
 			break;
 
-#ifndef CONFIG_ARM64_64K_PAGES
-		/*
-		 * For the first memory bank align the start address and
-		 * current memblock limit to prevent create_mapping() from
-		 * allocating pte page tables from unmapped memory.
-		 * When 64K pages are enabled, the pte page table for the
-		 * first PGDIR_SIZE is already present in swapper_pg_dir.
-		 */
-		if (start < limit)
-			start = ALIGN(start, PMD_SIZE);
-		if (end < limit) {
-			limit = end & PMD_MASK;
-			memblock_set_current_limit(limit);
+		if (ARM64_SWAPPER_USES_SECTION_MAPS) {
+			/*
+			 * For the first memory bank align the start address and
+			 * current memblock limit to prevent create_mapping() from
+			 * allocating pte page tables from unmapped memory. With
+			 * the section maps, if the first block doesn't end on section
+			 * size boundary, create_mapping() will try to allocate a pte
+			 * page, which may be returned from an unmapped area.
+			 * When section maps are not used, the pte page table for the
+			 * current limit is already present in swapper_pg_dir.
+			 */
+			if (start < limit)
+				start = ALIGN(start, SECTION_SIZE);
+			if (end < limit) {
+				limit = end & SECTION_MASK;
+				memblock_set_current_limit(limit);
+			}
 		}
-#endif
 		__map_memblock(start, end);
 	}
 
@@ -551,7 +552,7 @@ int kern_addr_valid(unsigned long addr)
 	return pfn_valid(pte_pfn(*pte));
 }
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
-#ifdef CONFIG_ARM64_64K_PAGES
+#if !ARM64_SWAPPER_USES_SECTION_MAPS
 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 {
 	return vmemmap_populate_basepages(start, end, node);
@@ -691,7 +692,7 @@ void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
 {
 	const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
 	pgprot_t prot = PAGE_KERNEL | PTE_RDONLY;
-	int granularity, size, offset;
+	int size, offset;
 	void *dt_virt;
 
 	/*
@@ -717,24 +718,15 @@ void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
 	 */
 	BUILD_BUG_ON(dt_virt_base % SZ_2M);
 
-	if (IS_ENABLED(CONFIG_ARM64_64K_PAGES)) {
-		BUILD_BUG_ON(__fix_to_virt(FIX_FDT_END) >> PMD_SHIFT !=
-			     __fix_to_virt(FIX_BTMAP_BEGIN) >> PMD_SHIFT);
-
-		granularity = PAGE_SIZE;
-	} else {
-		BUILD_BUG_ON(__fix_to_virt(FIX_FDT_END) >> PUD_SHIFT !=
-			     __fix_to_virt(FIX_BTMAP_BEGIN) >> PUD_SHIFT);
-
-		granularity = PMD_SIZE;
-	}
+	BUILD_BUG_ON(__fix_to_virt(FIX_FDT_END) >> SWAPPER_TABLE_SHIFT !=
+		     __fix_to_virt(FIX_BTMAP_BEGIN) >> SWAPPER_TABLE_SHIFT);
 
-	offset = dt_phys % granularity;
+	offset = dt_phys % SWAPPER_BLOCK_SIZE;
 	dt_virt = (void *)dt_virt_base + offset;
 
 	/* map the first chunk so we can read the size from the header */
-	create_mapping(round_down(dt_phys, granularity), dt_virt_base,
-		       granularity, prot);
+	create_mapping(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
+		       SWAPPER_BLOCK_SIZE, prot);
 
 	if (fdt_check_header(dt_virt) != 0)
 		return NULL;
@@ -743,9 +735,9 @@ void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
 	if (size > MAX_FDT_SIZE)
 		return NULL;
 
-	if (offset + size > granularity)
-		create_mapping(round_down(dt_phys, granularity), dt_virt_base,
-			       round_up(offset + size, granularity), prot);
+	if (offset + size > SWAPPER_BLOCK_SIZE)
+		create_mapping(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
+			       round_up(offset + size, SWAPPER_BLOCK_SIZE), prot);
 
 	memblock_reserve(dt_phys, size);
 
-- 
1.7.9.5

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#1246607

FromMark Rutland <mark.rutland@arm.com>
Date2015-10-14 14:10 +0200
Message-ID<qjt2y-6rP-15@gated-at.bofh.it>
In reply to#1246541
On Wed, Oct 14, 2015 at 12:20:25PM +0100, Suzuki K. Poulose wrote:
> We use section maps with 4K page size to create the swapper/idmaps.
> So far we have used !64K or 4K checks to handle the case where we
> use the section maps.
> This patch adds a new symbol, ARM64_SWAPPER_USES_SECTION_MAPS, to
> handle cases where we use section maps, instead of using the page size
> symbols.
> 
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
> ---
>  arch/arm64/include/asm/kernel-pgtable.h |   31 ++++++++-----
>  arch/arm64/mm/mmu.c                     |   72 ++++++++++++++-----------------
>  2 files changed, 52 insertions(+), 51 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
> index 622929d..5876a36 100644
> --- a/arch/arm64/include/asm/kernel-pgtable.h
> +++ b/arch/arm64/include/asm/kernel-pgtable.h
> @@ -19,6 +19,13 @@
>  #ifndef __ASM_KERNEL_PGTABLE_H
>  #define __ASM_KERNEL_PGTABLE_H
>  
> +/* With 4K pages, we use section maps. */
> +#ifdef CONFIG_ARM64_4K_PAGES
> +#define ARM64_SWAPPER_USES_SECTION_MAPS 1
> +#else
> +#define ARM64_SWAPPER_USES_SECTION_MAPS 0
> +#endif

The comment is somewhat redunant. It would be better to state why we do
this for 4K and not 64K (or 16K).

> @@ -406,14 +407,11 @@ static void __init map_mem(void)
>  	 * memory addressable from the initial direct kernel mapping.
>  	 *
>  	 * The initial direct kernel mapping, located at swapper_pg_dir, gives
> -	 * us PUD_SIZE (4K pages) or PMD_SIZE (64K pages) memory starting from
> -	 * PHYS_OFFSET (which must be aligned to 2MB as per
> -	 * Documentation/arm64/booting.txt).
> +	 * us PUD_SIZE (with SECTION maps, i.e, 4K) or PMD_SIZE (without
> +	 * SECTION maps, i.e, 64K pages) memory starting from PHYS_OFFSET
> +	 * (which must be aligned to 2MB as per Documentation/arm64/booting.txt).

This didn't seem to get updated for 16K later in the series, unless I
missed something.

Perhaps drop the mention of 4K / 64K entirely here?

> @@ -551,7 +552,7 @@ int kern_addr_valid(unsigned long addr)
>  	return pfn_valid(pte_pfn(*pte));
>  }
>  #ifdef CONFIG_SPARSEMEM_VMEMMAP
> -#ifdef CONFIG_ARM64_64K_PAGES
> +#if !ARM64_SWAPPER_USES_SECTION_MAPS

This leaves the comments on the #else and #endif stale. Please update
those too.

Otherwise this looks good!

Thanks,
Mark.
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#1246745

From"Suzuki K. Poulose" <Suzuki.Poulose@arm.com>
Date2015-10-14 15:30 +0200
Message-ID<qjuhZ-8cu-39@gated-at.bofh.it>
In reply to#1246607
On 14/10/15 13:06, Mark Rutland wrote:
> On Wed, Oct 14, 2015 at 12:20:25PM +0100, Suzuki K. Poulose wrote:
>> We use section maps with 4K page size to create the swapper/idmaps.
>> So far we have used !64K or 4K checks to handle the case where we
>> use the section maps.
>> This patch adds a new symbol, ARM64_SWAPPER_USES_SECTION_MAPS, to
>> handle cases where we use section maps, instead of using the page size
>> symbols.
>>
>> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Will Deacon <will.deacon@arm.com>
>> Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
>> ---
>>   arch/arm64/include/asm/kernel-pgtable.h |   31 ++++++++-----
>>   arch/arm64/mm/mmu.c                     |   72 ++++++++++++++-----------------
>>   2 files changed, 52 insertions(+), 51 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
>> index 622929d..5876a36 100644
>> --- a/arch/arm64/include/asm/kernel-pgtable.h
>> +++ b/arch/arm64/include/asm/kernel-pgtable.h
>> @@ -19,6 +19,13 @@
>>   #ifndef __ASM_KERNEL_PGTABLE_H
>>   #define __ASM_KERNEL_PGTABLE_H
>>
>> +/* With 4K pages, we use section maps. */
>> +#ifdef CONFIG_ARM64_4K_PAGES
>> +#define ARM64_SWAPPER_USES_SECTION_MAPS 1
>> +#else
>> +#define ARM64_SWAPPER_USES_SECTION_MAPS 0
>> +#endif
>
> The comment is somewhat redunant. It would be better to state why we do
> this for 4K and not 64K (or 16K).

Something like :

/*
  * ARM64 kernel is guaranteed to be loaded at 2M aligned
  * address (as per booting requirements). Hence we can use
  * section mapping with 4K (section size = 2M) and not with
  * 16K(section size = 32M) or 64K (section size = 512M).
  */

>> +	 * us PUD_SIZE (with SECTION maps, i.e, 4K) or PMD_SIZE (without
>> +	 * SECTION maps, i.e, 64K pages) memory starting from PHYS_OFFSET
>> +	 * (which must be aligned to 2MB as per Documentation/arm64/booting.txt).
>
> This didn't seem to get updated for 16K later in the series, unless I
> missed something.
>
> Perhaps drop the mention of 4K / 64K entirely here?

You are right, I missed it. We can drop the pagesize info entirely.

>
>> @@ -551,7 +552,7 @@ int kern_addr_valid(unsigned long addr)
>>   	return pfn_valid(pte_pfn(*pte));
>>   }
>>   #ifdef CONFIG_SPARSEMEM_VMEMMAP
>> -#ifdef CONFIG_ARM64_64K_PAGES
>> +#if !ARM64_SWAPPER_USES_SECTION_MAPS
>
> This leaves the comments on the #else and #endif stale. Please update
> those too.

Done.

Thanks
Suzuki

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#1246858

FromMark Rutland <mark.rutland@arm.com>
Date2015-10-14 17:00 +0200
Message-ID<qjvH3-1Iz-3@gated-at.bofh.it>
In reply to#1246745
> >>+/* With 4K pages, we use section maps. */
> >>+#ifdef CONFIG_ARM64_4K_PAGES
> >>+#define ARM64_SWAPPER_USES_SECTION_MAPS 1
> >>+#else
> >>+#define ARM64_SWAPPER_USES_SECTION_MAPS 0
> >>+#endif
> >
> >The comment is somewhat redunant. It would be better to state why we do
> >this for 4K and not 64K (or 16K).
> 
> Something like :
> 
> /*
>  * ARM64 kernel is guaranteed to be loaded at 2M aligned
>  * address (as per booting requirements). Hence we can use
>  * section mapping with 4K (section size = 2M) and not with
>  * 16K(section size = 32M) or 64K (section size = 512M).
>  */

That sounds much better. I hadn't figured out why myself, so thanks for
the explanation :)

However, there's one minor nit: the start of memory below the kernel is
2M aligned, but the offset means that the kernel itself is not loaded at
a 2M aligned address.

So how about:

/*
 * The linear mapping and the start of memory are both 2M aligned (per
 * the arm64 booting.txt requirements). Hence we can use section mapping
 * with 4K (section size = 2M) but not with 16K (section size = 32M) or
 * 64K (section size = 512M).
 */

> >>+	 * us PUD_SIZE (with SECTION maps, i.e, 4K) or PMD_SIZE (without
> >>+	 * SECTION maps, i.e, 64K pages) memory starting from PHYS_OFFSET
> >>+	 * (which must be aligned to 2MB as per Documentation/arm64/booting.txt).
> >
> >This didn't seem to get updated for 16K later in the series, unless I
> >missed something.
> >
> >Perhaps drop the mention of 4K / 64K entirely here?
> 
> You are right, I missed it. We can drop the pagesize info entirely.

Ok. Sounds good.

> >>@@ -551,7 +552,7 @@ int kern_addr_valid(unsigned long addr)
> >>  	return pfn_valid(pte_pfn(*pte));
> >>  }
> >>  #ifdef CONFIG_SPARSEMEM_VMEMMAP
> >>-#ifdef CONFIG_ARM64_64K_PAGES
> >>+#if !ARM64_SWAPPER_USES_SECTION_MAPS
> >
> >This leaves the comments on the #else and #endif stale. Please update
> >those too.
> 
> Done.

Great.

Thanks,
Mark.
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#1246868

From"Suzuki K. Poulose" <Suzuki.Poulose@arm.com>
Date2015-10-14 17:10 +0200
Message-ID<qjvQK-2a2-7@gated-at.bofh.it>
In reply to#1246858
On 14/10/15 15:51, Mark Rutland wrote:
>>>> +/* With 4K pages, we use section maps. */

>> /*
>>   * ARM64 kernel is guaranteed to be loaded at 2M aligned
>>   * address (as per booting requirements). Hence we can use
>>   * section mapping with 4K (section size = 2M) and not with
>>   * 16K(section size = 32M) or 64K (section size = 512M).
>>   */
>
> That sounds much better. I hadn't figured out why myself, so thanks for
> the explanation :)
>
> However, there's one minor nit: the start of memory below the kernel is
> 2M aligned, but the offset means that the kernel itself is not loaded at
> a 2M aligned address.

Oh yes

>
> So how about:
>
> /*
>   * The linear mapping and the start of memory are both 2M aligned (per
>   * the arm64 booting.txt requirements). Hence we can use section mapping
>   * with 4K (section size = 2M) but not with 16K (section size = 32M) or
>   * 64K (section size = 512M).
>   */

Will add this

Thanks
Suzuki

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#1246883

FromMark Rutland <mark.rutland@arm.com>
Date2015-10-14 17:20 +0200
Message-ID<qjw0q-2n4-23@gated-at.bofh.it>
In reply to#1246868
On Wed, Oct 14, 2015 at 04:08:43PM +0100, Suzuki K. Poulose wrote:
> On 14/10/15 15:51, Mark Rutland wrote:
> >>>>+/* With 4K pages, we use section maps. */
> 
> >>/*
> >>  * ARM64 kernel is guaranteed to be loaded at 2M aligned
> >>  * address (as per booting requirements). Hence we can use
> >>  * section mapping with 4K (section size = 2M) and not with
> >>  * 16K(section size = 32M) or 64K (section size = 512M).
> >>  */
> >
> >That sounds much better. I hadn't figured out why myself, so thanks for
> >the explanation :)
> >
> >However, there's one minor nit: the start of memory below the kernel is
> >2M aligned, but the offset means that the kernel itself is not loaded at
> >a 2M aligned address.
> 
> Oh yes
> 
> >
> >So how about:
> >
> >/*
> >  * The linear mapping and the start of memory are both 2M aligned (per
> >  * the arm64 booting.txt requirements). Hence we can use section mapping
> >  * with 4K (section size = 2M) but not with 16K (section size = 32M) or
> >  * 64K (section size = 512M).
> >  */
> 
> Will add this

Great.

FWIW, with the changes from this thread applied:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Thanks,
Mark.
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