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Subject[RFC V2 09/10] arm64/mm: Add FEAT_LPA2 specific fallback (48 bits PA) when not implemented
Date
CONFIG_ARM64_PA_BITS_52 build kernels need to fallback for 48 bits PA range
encodings when FEAT_LPA2 is not implemented i.e TCR_EL1.DS could not be set
. Hence modify applicable PTE and TTBR encoding helpers to accommodate the
scenario via 'arm64_lpa2_enabled'.

Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
arch/arm64/include/asm/assembler.h | 16 ++++++++++++++++
arch/arm64/include/asm/pgtable-hwdef.h | 2 ++
arch/arm64/include/asm/pgtable.h | 12 ++++++++++--
3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index d7ce4cf..ae69825 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -615,9 +615,17 @@ alternative_endif
orr \pte, \phys, \phys, lsr #36
and \pte, \pte, #PTE_ADDR_MASK
#elif defined(CONFIG_ARM64_PA_BITS_52_LPA2)
+ ldr_l \pte, arm64_lpa2_enabled
+ cmp \pte, #1
+ b.ne .Lskip_lpa2\@
+
orr \pte, \phys, \phys, lsr #42
and \pte, \pte, #PTE_ADDR_MASK | GENMASK(PAGE_SHIFT - 1, 10)
and \pte, \pte, #~GENMASK(PAGE_SHIFT - 1, 10)
+ b .Ldone_lpa2\@
+.Lskip_lpa2\@:
+ mov \pte, \phys
+.Ldone_lpa2\@:
#else /* !CONFIG_ARM64_PA_BITS_52_LPA */
mov \pte, \phys
#endif /* CONFIG_ARM64_PA_BITS_52_LPA */
@@ -629,9 +637,17 @@ alternative_endif
bfxil \phys, \pte, #PAGE_SHIFT, #(48 - PAGE_SHIFT)
lsl \phys, \phys, #PAGE_SHIFT
#elif defined(CONFIG_ARM64_PA_BITS_52_LPA2)
+ ldr_l \phys, arm64_lpa2_enabled
+ cmp \phys, #1
+ b.ne .Lskip_lpa2\@
+
ubfiz \phys, \pte, #(52 - PAGE_SHIFT - 10), #10
bfxil \phys, \pte, #PAGE_SHIFT, #(50 - PAGE_SHIFT)
lsl \phys, \phys, #PAGE_SHIFT
+ b .Ldone_lpa2\@
+.Lskip_lpa2\@:
+ and \phys, \pte, #PTE_ADDR_MASK_48
+.Ldone_lpa2\@:
#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 8a3b75e..b98b764 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -176,6 +176,8 @@
#define PTE_ADDR_MASK PTE_ADDR_LOW
#endif /* CONFIG_ARM64_PA_BITS_52_LPA */

+#define PTE_ADDR_MASK_48 (((_AT(pteval_t, 1) << (48 - PAGE_SHIFT)) - 1) << PAGE_SHIFT)
+
/*
* AttrIndx[2:0] encoding (mapping attributes defined in the MAIR* registers).
*/
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 5e7e402..97b3cd2 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -71,9 +71,17 @@ extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
((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) \
+#define __pte_to_phys_52(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)
+#define __phys_to_pte_val_52(phys) (((phys) | ((phys) >> 42)) & PTE_ADDR_MASK)
+
+#define __pte_to_phys_48(pte) (pte_val(pte) & PTE_ADDR_MASK_48)
+#define __phys_to_pte_val_48(phys) (phys)
+
+#define __pte_to_phys(pte) \
+ (arm64_lpa2_enabled ? __pte_to_phys_52(pte) : __pte_to_phys_48(pte))
+#define __phys_to_pte_val(phys) \
+ (arm64_lpa2_enabled ? __phys_to_pte_val_52(phys) : __phys_to_pte_val_48(phys))
#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)
--
2.7.4
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