Re: [RFC 06/10] arm64/mm: Add FEAT_LPA2 specific encoding

From: Steven Price
Date: Wed Jul 14 2021 - 11:38:20 EST

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In reply to: Anshuman Khandual: "[RFC 06/10] arm64/mm: Add FEAT_LPA2 specific encoding"
Next in thread: Anshuman Khandual: "[RFC 07/10] arm64/mm: Detect and enable FEAT_LPA2"
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On 14/07/2021 03:21, Anshuman Khandual wrote:
> FEAT_LPA2 requires different PTE representation formats for both 4K and 16K
> page size config. This adds FEAT_LPA2 specific new PTE encodings as per ARM
> ARM (0487G.A) which updates [pte|phys]_to_[phys|pte](). The updated helpers
> would be used when FEAT_LPA2 gets enabled via CONFIG_ARM64_PA_BITS_52 on 4K
> and 16K page size. Although TTBR encoding and phys_to_ttbr() helper remains
> the same as FEAT_LPA for FEAT_LPA2 as well. It updates 'phys_to_pte' helper
> to accept a temporary variable and changes impacted call sites.
>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
> arch/arm64/include/asm/assembler.h | 23 +++++++++++++++++++----
> arch/arm64/include/asm/pgtable-hwdef.h | 4 ++++
> arch/arm64/include/asm/pgtable.h | 4 ++++
> arch/arm64/kernel/head.S | 25 +++++++++++++------------
> 4 files changed, 40 insertions(+), 16 deletions(-)
>
> diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
> index fedc202..0492543 100644
> --- a/arch/arm64/include/asm/assembler.h
> +++ b/arch/arm64/include/asm/assembler.h
> @@ -606,7 +606,7 @@ alternative_endif
> #endif
> .endm
>
> - .macro phys_to_pte, pte, phys
> + .macro phys_to_pte, pte, phys, tmp
> #ifdef CONFIG_ARM64_PA_BITS_52_LPA
> /*
> * We assume \phys is 64K aligned and this is guaranteed by only
> @@ -614,6 +614,17 @@ alternative_endif
> */
> orr \pte, \phys, \phys, lsr #36
> and \pte, \pte, #PTE_ADDR_MASK
> +#elif defined(CONFIG_ARM64_PA_BITS_52_LPA2)
> + orr \pte, \phys, \phys, lsr #42
> +
> + /*
> + * The 'tmp' is being used here to just prepare
> + * and hold PTE_ADDR_MASK which cannot be passed
> + * to the subsequent 'and' instruction.
> + */
> + mov \tmp, #PTE_ADDR_LOW
> + orr \tmp, \tmp, #PTE_ADDR_HIGH
> + and \pte, \pte, \tmp

Rather than adding an extra temporary register (and the fallout of
various other macros needing an extra register), this can be done with
two AND instructions:

/* PTE_ADDR_MASK cannot be encoded as an immediate, so
* mask off all but two bits, followed by masking the
* extra two bits
*/
and \pte, \pte, #PTE_ADDR_MASK | (3 << 10)
and \pte, \pte, #~(3 << 10)

Steve

> #else /* !CONFIG_ARM64_PA_BITS_52_LPA */
> mov \pte, \phys
> #endif /* CONFIG_ARM64_PA_BITS_52_LPA */
> @@ -621,9 +632,13 @@ alternative_endif
>
> .macro pte_to_phys, phys, pte
> #ifdef CONFIG_ARM64_PA_BITS_52_LPA
> - ubfiz \phys, \pte, #(48 - 16 - 12), #16
> - bfxil \phys, \pte, #16, #32
> - lsl \phys, \phys, #16
> + ubfiz \phys, \pte, #(48 - PAGE_SHIFT - 12), #16
> + bfxil \phys, \pte, #PAGE_SHIFT, #(48 - PAGE_SHIFT)
> + lsl \phys, \phys, #PAGE_SHIFT
> +#elif defined(CONFIG_ARM64_PA_BITS_52_LPA2)
> + ubfiz \phys, \pte, #(52 - PAGE_SHIFT - 10), #10
> + bfxil \phys, \pte, #PAGE_SHIFT, #(50 - PAGE_SHIFT)
> + lsl \phys, \phys, #PAGE_SHIFT
> #else /* !CONFIG_ARM64_PA_BITS_52_LPA */
> and \phys, \pte, #PTE_ADDR_MASK
> #endif /* CONFIG_ARM64_PA_BITS_52_LPA */
> diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
> index f375bcf..c815a85 100644
> --- a/arch/arm64/include/asm/pgtable-hwdef.h
> +++ b/arch/arm64/include/asm/pgtable-hwdef.h
> @@ -159,6 +159,10 @@
> #define PTE_ADDR_LOW (((_AT(pteval_t, 1) << (48 - PAGE_SHIFT)) - 1) << PAGE_SHIFT)
> #define PTE_ADDR_HIGH (_AT(pteval_t, 0xf) << 12)
> #define PTE_ADDR_MASK (PTE_ADDR_LOW | PTE_ADDR_HIGH)
> +#elif defined(CONFIG_ARM64_PA_BITS_52_LPA2)
> +#define PTE_ADDR_LOW (((_AT(pteval_t, 1) << (50 - PAGE_SHIFT)) - 1) << PAGE_SHIFT)
> +#define PTE_ADDR_HIGH (_AT(pteval_t, 0x3) << 8)
> +#define PTE_ADDR_MASK (PTE_ADDR_LOW | PTE_ADDR_HIGH)
> #else /* !CONFIG_ARM64_PA_BITS_52_LPA */
> #define PTE_ADDR_LOW (((_AT(pteval_t, 1) << (48 - PAGE_SHIFT)) - 1) << PAGE_SHIFT)
> #define PTE_ADDR_MASK PTE_ADDR_LOW
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 3c57fb2..5e7e402 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -70,6 +70,10 @@ extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
> #define __pte_to_phys(pte) \
> ((pte_val(pte) & PTE_ADDR_LOW) | ((pte_val(pte) & PTE_ADDR_HIGH) << 36))
> #define __phys_to_pte_val(phys) (((phys) | ((phys) >> 36)) & PTE_ADDR_MASK)
> +#elif defined(CONFIG_ARM64_PA_BITS_52_LPA2)
> +#define __pte_to_phys(pte) \
> + ((pte_val(pte) & PTE_ADDR_LOW) | ((pte_val(pte) & PTE_ADDR_HIGH) << 42))
> +#define __phys_to_pte_val(phys) (((phys) | ((phys) >> 42)) & PTE_ADDR_MASK)
> #else /* !CONFIG_ARM64_PA_BITS_52_LPA */
> #define __pte_to_phys(pte) (pte_val(pte) & PTE_ADDR_MASK)
> #define __phys_to_pte_val(phys) (phys)
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index c5c994a..6444147 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -134,9 +134,9 @@ SYM_CODE_END(preserve_boot_args)
> * Corrupts: ptrs, tmp1, tmp2
> * Returns: tbl -> next level table page address
> */
> - .macro create_table_entry, tbl, virt, shift, ptrs, tmp1, tmp2
> + .macro create_table_entry, tbl, virt, shift, ptrs, tmp1, tmp2, tmp3
> add \tmp1, \tbl, #PAGE_SIZE
> - phys_to_pte \tmp2, \tmp1
> + phys_to_pte \tmp2, \tmp1, \tmp3
> orr \tmp2, \tmp2, #PMD_TYPE_TABLE // address of next table and entry type
> lsr \tmp1, \virt, #\shift
> sub \ptrs, \ptrs, #1
> @@ -161,8 +161,8 @@ SYM_CODE_END(preserve_boot_args)
> * Corrupts: index, tmp1
> * Returns: rtbl
> */
> - .macro populate_entries, tbl, rtbl, index, eindex, flags, inc, tmp1
> -.Lpe\@: phys_to_pte \tmp1, \rtbl
> + .macro populate_entries, tbl, rtbl, index, eindex, flags, inc, tmp1, tmp2
> +.Lpe\@: phys_to_pte \tmp1, \rtbl, \tmp2
> orr \tmp1, \tmp1, \flags // tmp1 = table entry
> str \tmp1, [\tbl, \index, lsl #3]
> add \rtbl, \rtbl, \inc // rtbl = pa next level
> @@ -224,31 +224,32 @@ SYM_CODE_END(preserve_boot_args)
> * Preserves: vstart, vend, flags
> * Corrupts: tbl, rtbl, istart, iend, tmp, count, sv
> */
> - .macro map_memory, tbl, rtbl, vstart, vend, flags, phys, pgds, istart, iend, tmp, count, sv
> + .macro map_memory, tbl, rtbl, vstart, vend, flags, phys, pgds, istart, iend, \
> + tmp, tmp1, count, sv
> add \rtbl, \tbl, #PAGE_SIZE
> mov \sv, \rtbl
> mov \count, #0
> compute_indices \vstart, \vend, #PGDIR_SHIFT, \pgds, \istart, \iend, \count
> - populate_entries \tbl, \rtbl, \istart, \iend, #PMD_TYPE_TABLE, #PAGE_SIZE, \tmp
> + populate_entries \tbl, \rtbl, \istart, \iend, #PMD_TYPE_TABLE, #PAGE_SIZE, \tmp, \tmp1
> mov \tbl, \sv
> mov \sv, \rtbl
>
> #if SWAPPER_PGTABLE_LEVELS > 3
> compute_indices \vstart, \vend, #PUD_SHIFT, #PTRS_PER_PUD, \istart, \iend, \count
> - populate_entries \tbl, \rtbl, \istart, \iend, #PMD_TYPE_TABLE, #PAGE_SIZE, \tmp
> + populate_entries \tbl, \rtbl, \istart, \iend, #PMD_TYPE_TABLE, #PAGE_SIZE, \tmp, \tmp1
> mov \tbl, \sv
> mov \sv, \rtbl
> #endif
>
> #if SWAPPER_PGTABLE_LEVELS > 2
> compute_indices \vstart, \vend, #SWAPPER_TABLE_SHIFT, #PTRS_PER_PMD, \istart, \iend, \count
> - populate_entries \tbl, \rtbl, \istart, \iend, #PMD_TYPE_TABLE, #PAGE_SIZE, \tmp
> + populate_entries \tbl, \rtbl, \istart, \iend, #PMD_TYPE_TABLE, #PAGE_SIZE, \tmp, \tmp1
> mov \tbl, \sv
> #endif
>
> compute_indices \vstart, \vend, #SWAPPER_BLOCK_SHIFT, #PTRS_PER_PTE, \istart, \iend, \count
> bic \count, \phys, #SWAPPER_BLOCK_SIZE - 1
> - populate_entries \tbl, \count, \istart, \iend, \flags, #SWAPPER_BLOCK_SIZE, \tmp
> + populate_entries \tbl, \count, \istart, \iend, \flags, #SWAPPER_BLOCK_SIZE, \tmp, \tmp1
> .endm
>
> /*
> @@ -343,7 +344,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
> #endif
>
> mov x4, EXTRA_PTRS
> - create_table_entry x0, x3, EXTRA_SHIFT, x4, x5, x6
> + create_table_entry x0, x3, EXTRA_SHIFT, x4, x5, x6, x20
> #else
> /*
> * If VA_BITS == 48, we don't have to configure an additional
> @@ -356,7 +357,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
> ldr_l x4, idmap_ptrs_per_pgd
> adr_l x6, __idmap_text_end // __pa(__idmap_text_end)
>
> - map_memory x0, x1, x3, x6, x7, x3, x4, x10, x11, x12, x13, x14
> + map_memory x0, x1, x3, x6, x7, x3, x4, x10, x11, x12, x20, x13, x14
>
> /*
> * Map the kernel image (starting with PHYS_OFFSET).
> @@ -370,7 +371,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
> sub x6, x6, x3 // _end - _text
> add x6, x6, x5 // runtime __va(_end)
>
> - map_memory x0, x1, x5, x6, x7, x3, x4, x10, x11, x12, x13, x14
> + map_memory x0, x1, x5, x6, x7, x3, x4, x10, x11, x12, x20, x13, x14
>
> /*
> * Since the page tables have been populated with non-cacheable
>

Next message: Rob Herring: "Re: [PATCH 1/5] dt-bindings: virtio: mmio: Add support for device subnode"
Previous message: Theodore Y. Ts'o: "Re: 5.13.2-rc and others have many not for stable"
In reply to: Anshuman Khandual: "[RFC 06/10] arm64/mm: Add FEAT_LPA2 specific encoding"
Next in thread: Anshuman Khandual: "[RFC 07/10] arm64/mm: Detect and enable FEAT_LPA2"
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