[PATCH v12 15/17] arm64: kexec: keep MMU enabled during kexec relocation
Pavel Tatashin
pasha.tatashin at soleen.com
Wed Mar 3 00:22:28 GMT 2021
Now, that we have linear map page tables configured, keep MMU enabled
to allow faster relocation of segments to final destination.
The performance data: for a moderate size kernel + initramfs: 25M the
relocation was taking 0.382s, with enabled MMU it now takes
0.019s only or x20 improvement.
The time is proportional to the size of relocation, therefore if initramfs
is larger, 100M it could take over a second.
Signed-off-by: Pavel Tatashin <pasha.tatashin at soleen.com>
---
arch/arm64/include/asm/kexec.h | 3 +++
arch/arm64/kernel/asm-offsets.c | 1 +
arch/arm64/kernel/machine_kexec.c | 16 ++++++++++----
arch/arm64/kernel/relocate_kernel.S | 33 +++++++++++++++++++----------
4 files changed, 38 insertions(+), 15 deletions(-)
diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index 59ac166daf53..5fc87b51f8a9 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -97,8 +97,11 @@ struct kimage_arch {
phys_addr_t dtb_mem;
phys_addr_t kern_reloc;
phys_addr_t el2_vectors;
+ phys_addr_t ttbr0;
phys_addr_t ttbr1;
phys_addr_t zero_page;
+ unsigned long phys_offset;
+ unsigned long t0sz;
/* Core ELF header buffer */
void *elf_headers;
unsigned long elf_headers_mem;
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 609362b5aa76..ec7bb80aedc8 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -159,6 +159,7 @@ int main(void)
DEFINE(KIMAGE_ARCH_DTB_MEM, offsetof(struct kimage, arch.dtb_mem));
DEFINE(KIMAGE_ARCH_EL2_VECTORS, offsetof(struct kimage, arch.el2_vectors));
DEFINE(KIMAGE_ARCH_ZERO_PAGE, offsetof(struct kimage, arch.zero_page));
+ DEFINE(KIMAGE_ARCH_PHYS_OFFSET, offsetof(struct kimage, arch.phys_offset));
DEFINE(KIMAGE_ARCH_TTBR1, offsetof(struct kimage, arch.ttbr1));
DEFINE(KIMAGE_HEAD, offsetof(struct kimage, head));
DEFINE(KIMAGE_START, offsetof(struct kimage, start));
diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index c875ef522e53..d5c8aefc66f3 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -190,6 +190,11 @@ int machine_kexec_post_load(struct kimage *kimage)
reloc_size = __relocate_new_kernel_end - __relocate_new_kernel_start;
memcpy(reloc_code, __relocate_new_kernel_start, reloc_size);
kimage->arch.kern_reloc = __pa(reloc_code);
+ rc = trans_pgd_idmap_page(&info, &kimage->arch.ttbr0,
+ &kimage->arch.t0sz, reloc_code);
+ if (rc)
+ return rc;
+ kimage->arch.phys_offset = virt_to_phys(kimage) - (long)kimage;
/* Flush the reloc_code in preparation for its execution. */
__flush_dcache_area(reloc_code, reloc_size);
@@ -223,9 +228,9 @@ void machine_kexec(struct kimage *kimage)
local_daif_mask();
/*
- * Both restart and cpu_soft_restart will shutdown the MMU, disable data
+ * Both restart and kernel_reloc will shutdown the MMU, disable data
* caches. However, restart will start new kernel or purgatory directly,
- * cpu_soft_restart will transfer control to arm64_relocate_new_kernel
+ * kernel_reloc contains the body of arm64_relocate_new_kernel
* In kexec case, kimage->start points to purgatory assuming that
* kernel entry and dtb address are embedded in purgatory by
* userspace (kexec-tools).
@@ -239,10 +244,13 @@ void machine_kexec(struct kimage *kimage)
restart(is_hyp_callable(), kimage->start, kimage->arch.dtb_mem,
0, 0);
} else {
+ void (*kernel_reloc)(struct kimage *kimage);
+
if (is_hyp_callable())
__hyp_set_vectors(kimage->arch.el2_vectors);
- cpu_soft_restart(kimage->arch.kern_reloc,
- virt_to_phys(kimage), 0, 0);
+ cpu_install_ttbr0(kimage->arch.ttbr0, kimage->arch.t0sz);
+ kernel_reloc = (void *)kimage->arch.kern_reloc;
+ kernel_reloc(kimage);
}
BUG(); /* Should never get here. */
diff --git a/arch/arm64/kernel/relocate_kernel.S b/arch/arm64/kernel/relocate_kernel.S
index e83b6380907d..8ac4b2d7f5e8 100644
--- a/arch/arm64/kernel/relocate_kernel.S
+++ b/arch/arm64/kernel/relocate_kernel.S
@@ -4,6 +4,8 @@
*
* Copyright (C) Linaro.
* Copyright (C) Huawei Futurewei Technologies.
+ * Copyright (C) 2020, Microsoft Corporation.
+ * Pavel Tatashin <pasha.tatashin at soleen.com>
*/
#include <linux/kexec.h>
@@ -15,6 +17,15 @@
#include <asm/sysreg.h>
#include <asm/virt.h>
+.macro turn_off_mmu tmp1, tmp2
+ mrs \tmp1, sctlr_el1
+ mov_q \tmp2, SCTLR_ELx_FLAGS
+ bic \tmp1, \tmp1, \tmp2
+ pre_disable_mmu_workaround
+ msr sctlr_el1, \tmp1
+ isb
+.endm
+
.pushsection ".kexec_relocate.text", "ax"
/*
* arm64_relocate_new_kernel - Put a 2nd stage image in place and boot it.
@@ -32,22 +43,21 @@ SYM_CODE_START(arm64_relocate_new_kernel)
ldr x18, [x0, #KIMAGE_ARCH_ZERO_PAGE] /* x18 = zero page for BBM */
ldr x17, [x0, #KIMAGE_ARCH_TTBR1] /* x17 = linear map copy */
ldr x16, [x0, #KIMAGE_HEAD] /* x16 = kimage_head */
- mov x14, xzr /* x14 = entry ptr */
- mov x13, xzr /* x13 = copy dest */
+ ldr x22, [x0, #KIMAGE_ARCH_PHYS_OFFSET] /* x22 phys_offset */
raw_dcache_line_size x15, x1 /* x15 = dcache line size */
break_before_make_ttbr_switch x18, x17, x1, x2 /* set linear map */
.Lloop:
and x12, x16, PAGE_MASK /* x12 = addr */
-
+ sub x12, x12, x22 /* Convert x12 to virt */
/* Test the entry flags. */
.Ltest_source:
tbz x16, IND_SOURCE_BIT, .Ltest_indirection
/* Invalidate dest page to PoC. */
- mov x2, x13
- mov x1, #PAGE_SIZE
- dcache_by_myline_op ivac, sy, x2, x1, x15, x20
+ mov x19, x13
copy_page x13, x12, x1, x2, x3, x4, x5, x6, x7, x8
+ mov x1, #PAGE_SIZE
+ dcache_by_myline_op ivac, sy, x19, x1, x15, x20
b .Lnext
.Ltest_indirection:
tbz x16, IND_INDIRECTION_BIT, .Ltest_destination
@@ -64,19 +74,20 @@ SYM_CODE_START(arm64_relocate_new_kernel)
ic iallu
dsb nsh
isb
+ ldr x4, [x0, #KIMAGE_START] /* relocation start */
+ ldr x1, [x0, #KIMAGE_ARCH_EL2_VECTORS] /* relocation start */
+ ldr x0, [x0, #KIMAGE_ARCH_DTB_MEM] /* dtb address */
+ turn_off_mmu x12, x13
/* Start new image. */
- ldr x1, [x0, #KIMAGE_ARCH_EL2_VECTORS] /* relocation start */
cbz x1, .Lel1
- ldr x1, [x0, #KIMAGE_START] /* relocation start */
- ldr x2, [x0, #KIMAGE_ARCH_DTB_MEM] /* dtb address */
+ mov x1, x4 /* relocation start */
+ mov x2, x0 /* dtb address */
mov x3, xzr
mov x4, xzr
mov x0, #HVC_SOFT_RESTART
hvc #0 /* Jumps from el2 */
.Lel1:
- ldr x4, [x0, #KIMAGE_START] /* relocation start */
- ldr x0, [x0, #KIMAGE_ARCH_DTB_MEM] /* dtb address */
mov x2, xzr
mov x3, xzr
br x4 /* Jumps from el1 */
--
2.25.1
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