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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v2 24/35] xen/arm32: head: Introduce distinct paths for the boot CPU and secondary CPUs
The boot code is currently quite difficult to go through because of the
lack of documentation and a number of indirection to avoid executing
some path in either the boot CPU or secondary CPUs.
In an attempt to make the boot code easier to follow, each parts of the
boot are now in separate functions. Furthermore, the paths for the boot
CPU and secondary CPUs are now distinct and for now will call each
functions.
Follow-ups will remove unnecessary calls and do further improvement
(such as adding documentation and reshuffling).
Note that the switch from using the ID mapping to the runtime mapping
is duplicated for each path. This is because in the future we will need
to stay longer in the ID mapping for the boot CPU.
Lastly, it is now required to save lr in cpu_init() becauswe the
function will call other functions and therefore clobber lr.
Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
---
Changes in v2:
- Patch added
---
xen/arch/arm/arm32/head.S | 64 +++++++++++++++++++++++++++++++++++++++--------
1 file changed, 53 insertions(+), 11 deletions(-)
diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
index bbcfdcd351..13793e85d8 100644
--- a/xen/arch/arm/arm32/head.S
+++ b/xen/arch/arm/arm32/head.S
@@ -148,7 +148,19 @@ past_zImage:
mov r12, #0 /* r12 := is_secondary_cpu */
- b common_start
+ bl check_cpu_mode
+ bl zero_bss
+ bl cpu_init
+ bl create_page_tables
+ bl enable_mmu
+
+ /* We are still in the ID map. Jump to the runtime Virtual Address */
+ ldr r0, =primary_switched
+ mov pc, r0
+primary_switched:
+ bl setup_fixmap
+ b launch
+ENDPROC(start)
GLOBAL(init_secondary)
cpsid aif /* Disable all interrupts */
@@ -179,8 +191,21 @@ GLOBAL(init_secondary)
print_reg r7
PRINT(" booting -\r\n")
#endif
-
-common_start:
+ bl check_cpu_mode
+ bl zero_bss
+ bl cpu_init
+ bl create_page_tables
+ bl enable_mmu
+
+ /* We are still in the ID map. Jump to the runtime Virtual Address. */
+ ldr r0, =secondary_switched
+ mov pc, r0
+secondary_switched:
+ bl setup_fixmap
+ b launch
+ENDPROC(init_secondary)
+
+check_cpu_mode:
/* Check that this CPU has Hyp mode */
mrc CP32(r0, ID_PFR1)
and r0, r0, #0xf000 /* Bits 12-15 define virt extensions */
@@ -202,7 +227,10 @@ common_start:
b fail
hyp: PRINT("- Xen starting in Hyp mode -\r\n")
+ mov pc, lr
+ENDPROC(check_cpu_mode)
+zero_bss:
/* Zero BSS On the boot CPU to avoid nasty surprises */
teq r12, #0
bne skip_bss
@@ -219,8 +247,14 @@ hyp: PRINT("- Xen starting in Hyp mode -\r\n")
blo 1b
skip_bss:
+ mov pc, lr
+ENDPROC(zero_bss)
+
+cpu_init:
PRINT("- Setting up control registers -\r\n")
+ mov r5, lr /* r5 := return address */
+
/* Get processor specific proc info into r1 */
bl __lookup_processor_type
teq r1, #0
@@ -231,7 +265,6 @@ skip_bss:
PRINT(" -\r\n")
b fail
1:
-
/* Jump to cpu_init */
ldr r1, [r1, #PROCINFO_cpu_init] /* r1 := vaddr(init func) */
adr lr, cpu_init_done /* Save return address */
@@ -256,6 +289,10 @@ cpu_init_done:
ldr r0, =HSCTLR_SET
mcr CP32(r0, HSCTLR)
+ mov pc, r5 /* Return address is in r5 */
+ENDPROC(cpu_init)
+
+create_page_tables:
/*
* Rebuild the boot pagetable's first-level entries. The structure
* is described in mm.c.
@@ -359,15 +396,16 @@ cpu_init_done:
/* boot pagetable setup complete */
cmp r6, #1 /* Did we manage to create an identity
mapping ? */
- beq 1f
+ moveq pc, lr
PRINT("Unable to build boot page tables - Failed to identity map
Xen.\r\n")
b fail
virtphys_clash:
/* Identity map clashes with boot_third, which we cannot handle yet */
PRINT("- Unable to build boot page tables - virt and phys addresses
clash. -\r\n")
b fail
+ENDPROC(create_page_tables)
-1:
+enable_mmu:
PRINT("- Turning on paging -\r\n")
/*
@@ -377,16 +415,16 @@ virtphys_clash:
mcr CP32(r0, TLBIALLH) /* Flush hypervisor TLBs */
dsb nsh
- ldr r1, =paging /* Explicit vaddr, not RIP-relative */
mrc CP32(r0, HSCTLR)
/* Enable MMU and D-cache */
orr r0, r0, #(SCTLR_Axx_ELx_M|SCTLR_Axx_ELx_C)
dsb /* Flush PTE writes and finish reads */
mcr CP32(r0, HSCTLR) /* now paging is enabled */
isb /* Now, flush the icache */
- mov pc, r1 /* Get a proper vaddr into PC */
-paging:
+ mov pc, lr
+ENDPROC(enable_mmu)
+setup_fixmap:
/*
* Now we can install the fixmap and dtb mappings, since we
* don't need the 1:1 map any more
@@ -436,12 +474,15 @@ paging:
mcr CP32(r0, TLBIALLH) /* Flush hypervisor TLB */
dsb /* Ensure completion of TLB flush */
isb
+ mov pc, lr
+ENDPROC(setup_fixmap)
+launch:
PRINT("- Ready -\r\n")
/* The boot CPU should go straight into C now */
teq r12, #0
- beq launch
+ beq 1f
/*
* Non-boot CPUs need to move on to the proper pagetables, which were
@@ -460,7 +501,7 @@ paging:
dsb /* Ensure completion of TLB+BP flush */
isb
-launch:
+1:
ldr r0, =init_data
add r0, #INITINFO_stack /* Find the boot-time stack */
ldr sp, [r0]
@@ -471,6 +512,7 @@ launch:
moveq r1, r8 /* - DTB address */
beq start_xen /* and disappear into the land of C */
b start_secondary /* (to the appropriate entry point) */
+ENDPROC(launch)
/* Fail-stop */
fail: PRINT("- Boot failed -\r\n")
--
2.11.0
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