Re: [RFC 07/10] arm64/mm: Detect and enable FEAT_LPA2
From: Suzuki K Poulose
Date: Wed Jul 14 2021 - 04:21:05 EST
On 14/07/2021 03:21, Anshuman Khandual wrote:
Detect FEAT_LPA2 implementation early enough during boot when requested via
CONFIG_ARM64_PA_BITS_52_LPA2 and remember in a variable arm64_lpa2_enabled.
This variable could then be used to turn on TCR_EL1.TCR_DS effecting the 52
bits PA range or fall back to default 48 bits PA range if FEAT_LPA2 feature
was requested but found not to be implemented.
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
arch/arm64/include/asm/memory.h | 1 +
arch/arm64/kernel/head.S | 15 +++++++++++++++
arch/arm64/mm/mmu.c | 3 +++
arch/arm64/mm/proc.S | 9 +++++++++
4 files changed, 28 insertions(+)
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 824a365..d0ca002 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -178,6 +178,7 @@
#include <asm/bug.h>
extern u64 vabits_actual;
+extern u64 arm64_lpa2_enabled;
extern s64 memstart_addr;
/* PHYS_OFFSET - the physical address of the start of memory. */
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 6444147..9cf79ea 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -94,6 +94,21 @@ SYM_CODE_START(primary_entry)
adrp x23, __PHYS_OFFSET
and x23, x23, MIN_KIMG_ALIGN - 1 // KASLR offset, defaults to 0
bl set_cpu_boot_mode_flag
+
+#ifdef CONFIG_ARM64_PA_BITS_52_LPA2
+ mrs x10, ID_AA64MMFR0_EL1
+ ubfx x10, x10, #ID_AA64MMFR0_TGRAN_SHIFT, 4
+ cmp x10, #ID_AA64MMFR0_TGRAN_LPA2
+ b.ne 1f
For the sake of forward compatibility, this should be "b.lt"
Suzuki