On Mon, 22 Jul 2019, Julien Grall wrote:
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 */
The arm64 patch has been switched to use "1:1", it would be good to be
consistent. In the commit message too.
+ 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. */
Same here.
+ 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 */
Please align the comment with the others in this proc.
