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Subject[PATCH v2 2/2] ARM: support PHYS_OFFSET minimum aligned at 64KiB boundary
Date
Currently, only support the kernels where the base of physical memory is
at a 16MiB boundary. Because the add/sub instructions only contains 8bits
unrotated value. But we can use one more "add/sub" instructions to handle
bits 23-16. The performance will be slightly affected.

Since most boards meet 16 MiB alignment, so add a new configuration
option ARM_PATCH_PHYS_VIRT_RADICAL (default n) to control it. Say Y if
anyone really needs it.

All r0-r7 (r1 = machine no, r2 = atags or dtb, in the start-up phase) are
used in __fixup_a_pv_table() now, but the callee saved r11 is not used in
the whole head.S file. So choose it.

Because the calculation of "y = x + __pv_offset[63:24]" have been done,
so we only need to calculate "y = y + __pv_offset[23:16]", that's why
the parameters "to" and "from" of __pv_stub() and __pv_add_carry_stub()
in the scope of CONFIG_ARM_PATCH_PHYS_VIRT_RADICAL are all passed "t"
(above y).

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
arch/arm/Kconfig | 18 +++++++++++++++++-
arch/arm/include/asm/memory.h | 16 +++++++++++++---
arch/arm/kernel/head.S | 25 +++++++++++++++++++------
3 files changed, 49 insertions(+), 10 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index e00d94b16658765..19fc2c746e2ce29 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -240,12 +240,28 @@ config ARM_PATCH_PHYS_VIRT
kernel in system memory.

This can only be used with non-XIP MMU kernels where the base
- of physical memory is at a 16MB boundary.
+ of physical memory is at a 16MiB boundary.

Only disable this option if you know that you do not require
this feature (eg, building a kernel for a single machine) and
you need to shrink the kernel to the minimal size.

+config ARM_PATCH_PHYS_VIRT_RADICAL
+ bool "Support PHYS_OFFSET minimum aligned at 64KiB boundary"
+ default n
+ depends on ARM_PATCH_PHYS_VIRT
+ depends on !THUMB2_KERNEL
+ help
+ This can only be used with non-XIP MMU kernels where the base
+ of physical memory is at a 64KiB boundary.
+
+ Compared with ARM_PATCH_PHYS_VIRT, one or two more instructions
+ need to be added to implement the conversion of bits 23-16 of
+ the VA/PA in phys-to-virt and virt-to-phys. The performance is
+ slightly affected.
+
+ If unsure say N here.
+
config NEED_MACH_IO_H
bool
help
diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index 99035b5891ef442..71b3a60eeb1b1c6 100644
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h
@@ -173,6 +173,7 @@
* so that all we need to do is modify the 8-bit constant field.
*/
#define __PV_BITS_31_24 0x81000000
+#define __PV_BITS_23_16 0x00810000
#define __PV_BITS_7_0 0x81

extern unsigned long __pv_phys_pfn_offset;
@@ -201,7 +202,7 @@
: "=r" (t) \
: "I" (__PV_BITS_7_0))

-#define __pv_add_carry_stub(x, y) \
+#define __pv_add_carry_stub(x, y, type) \
__asm__ volatile("@ __pv_add_carry_stub\n" \
"1: adds %Q0, %1, %2\n" \
" adc %R0, %R0, #0\n" \
@@ -209,7 +210,7 @@
" .long 1b\n" \
" .popsection\n" \
: "+r" (y) \
- : "r" (x), "I" (__PV_BITS_31_24) \
+ : "r" (x), "I" (type) \
: "cc")

static inline phys_addr_t __virt_to_phys_nodebug(unsigned long x)
@@ -218,9 +219,15 @@ static inline phys_addr_t __virt_to_phys_nodebug(unsigned long x)

if (sizeof(phys_addr_t) == 4) {
__pv_stub(x, t, "add", __PV_BITS_31_24);
+#ifdef CONFIG_ARM_PATCH_PHYS_VIRT_RADICAL
+ __pv_stub(t, t, "add", __PV_BITS_23_16);
+#endif
} else {
__pv_stub_mov_hi(t);
- __pv_add_carry_stub(x, t);
+ __pv_add_carry_stub(x, t, __PV_BITS_31_24);
+#ifdef CONFIG_ARM_PATCH_PHYS_VIRT_RADICAL
+ __pv_add_carry_stub(t, t, __PV_BITS_23_16);
+#endif
}
return t;
}
@@ -236,6 +243,9 @@ static inline unsigned long __phys_to_virt(phys_addr_t x)
* in place where 'r' 32 bit operand is expected.
*/
__pv_stub((unsigned long) x, t, "sub", __PV_BITS_31_24);
+#ifdef CONFIG_ARM_PATCH_PHYS_VIRT_RADICAL
+ __pv_stub((unsigned long) t, t, "sub", __PV_BITS_23_16);
+#endif
return t;
}

diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 02d78c9198d0e8d..d9fb226a24d43ae 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -120,7 +120,7 @@ ENTRY(stext)
bl __fixup_smp
#endif
#ifdef CONFIG_ARM_PATCH_PHYS_VIRT
- bl __fixup_pv_table
+ bl __fixup_pv_table @r11 will be used
#endif
bl __create_page_tables

@@ -614,8 +614,13 @@ __fixup_pv_table:
mov r0, r8, lsr #PAGE_SHIFT @ convert to PFN
str r0, [r6] @ save computed PHYS_PFN_OFFSET to __pv_phys_pfn_offset
strcc ip, [r7, #HIGH_OFFSET] @ save to __pv_offset high bits
+#ifdef CONFIG_ARM_PATCH_PHYS_VIRT_RADICAL
+ mov r6, r3, lsr #16 @ constant for add/sub instructions
+ teq r3, r6, lsl #16 @ must be 64KiB aligned
+#else
mov r6, r3, lsr #24 @ constant for add/sub instructions
teq r3, r6, lsl #24 @ must be 16MiB aligned
+#endif
THUMB( it ne @ cross section branch )
bne __error
str r3, [r7, #LOW_OFFSET] @ save to __pv_offset low bits
@@ -636,7 +641,9 @@ __fixup_a_pv_table:
add r6, r6, r3
ldr r0, [r6, #HIGH_OFFSET] @ __pv_offset high word
ldr r6, [r6, #LOW_OFFSET] @ __pv_offset low word
- mov r6, r6, lsr #24
+ mov r11, r6, lsl #8
+ mov r11, r11, lsr #24 @ bits 23-16
+ mov r6, r6, lsr #24 @ bits 31-24
cmn r0, #1
#ifdef CONFIG_THUMB2_KERNEL
moveq r0, #0x200000 @ set bit 21, mov to mvn instruction
@@ -682,14 +689,20 @@ ARM_BE8(rev16 ip, ip)
#ifdef CONFIG_CPU_ENDIAN_BE8
@ in BE8, we load data in BE, but instructions still in LE
bic ip, ip, #0xff000000
- tst ip, #0x000f0000 @ check the rotation field
+ tst ip, #0x00040000 @ check the rotation field
orrne ip, ip, r6, lsl #24 @ mask in offset bits 31-24
+ tst ip, #0x00080000 @ check the rotation field
+ orrne ip, ip, r11, lsl #24 @ mask in offset bits 23-16
+ tst ip, #0x000f0000 @ check the rotation field
biceq ip, ip, #0x00004000 @ clear bit 22
orreq ip, ip, r0 @ mask in offset bits 7-0
#else
bic ip, ip, #0x000000ff
- tst ip, #0xf00 @ check the rotation field
+ tst ip, #0x400 @ check the rotation field
orrne ip, ip, r6 @ mask in offset bits 31-24
+ tst ip, #0x800 @ check the rotation field
+ orrne ip, ip, r11 @ mask in offset bits 23-16
+ tst ip, #0xf00 @ check the rotation field
biceq ip, ip, #0x400000 @ clear bit 22
orreq ip, ip, r0 @ mask in offset bits 7-0
#endif
@@ -705,12 +718,12 @@ ENDPROC(__fixup_a_pv_table)
3: .long __pv_offset

ENTRY(fixup_pv_table)
- stmfd sp!, {r4 - r7, lr}
+ stmfd sp!, {r4 - r7, r11, lr}
mov r3, #0 @ no offset
mov r4, r0 @ r0 = table start
add r5, r0, r1 @ r1 = table size
bl __fixup_a_pv_table
- ldmfd sp!, {r4 - r7, pc}
+ ldmfd sp!, {r4 - r7, r11, pc}
ENDPROC(fixup_pv_table)

.data
--
1.8.3

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