[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Xen-devel] [PATCH 16/17] xen/arm64: head: Rework and document launch()
Hi Stefano,
On 6/26/19 8:12 PM, Stefano Stabellini wrote:
On Mon, 10 Jun 2019, Julien Grall wrote:
Boot CPU and secondary CPUs will use different entry point to C code. At
the moment, the decision on which entry to use is taken within launch().
In order to avoid a branch for the decision and make the code clearer,
launch() is reworked to take in parameters the entry point and its
arguments.
Lastly, document the behavior and the main registers usage within the
function.
Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
---
xen/arch/arm/arm64/head.S | 41 +++++++++++++++++++++++++----------------
1 file changed, 25 insertions(+), 16 deletions(-)
diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index 4f7fa6769f..130ab66d8e 100644
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -312,6 +312,11 @@ primary_switched:
/* Use a virtual address to access the UART. */
ldr x23, =EARLY_UART_VIRTUAL_ADDRESS
#endif
+ PRINT("- Ready -\r\n")
+ /* Setup the arguments for start_xen and jump to C world */
+ mov x0, x20 /* x0 := phys_offset */
+ mov x1, x21 /* x1 := paddr(FDT) */
+ ldr x2, =start_xen
b launch
ENDPROC(real_start)
@@ -374,6 +379,9 @@ secondary_switched:
/* Use a virtual address to access the UART. */
ldr x23, =EARLY_UART_VIRTUAL_ADDRESS
#endif
+ PRINT("- Ready -\r\n")
+ /* Jump to C world */
+ ldr x2, =start_secondary
b launch
ENDPROC(init_secondary)
@@ -734,23 +742,24 @@ setup_fixmap:
ret
ENDPROC(setup_fixmap)
+/*
+ * Setup the initial stack and jump to the C world
+ *
+ * Inputs:
+ * x0 : Argument 0 of the C function to call
+ * x1 : Argument 1 of the C function to call
+ * x2 : C entry point
I know it is the last one before C-land, but we might as well add a
"Clobbers" section too, just in case. Here it clobbers x4 (or x3, see
below).
Sure.
+ */
launch:
- PRINT("- Ready -\r\n")
-
- ldr x0, =init_data
- add x0, x0, #INITINFO_stack /* Find the boot-time stack */
- ldr x0, [x0]
- add x0, x0, #STACK_SIZE /* (which grows down from the top). */
- sub x0, x0, #CPUINFO_sizeof /* Make room for CPU save record */
- mov sp, x0
-
- cbnz x22, 1f
-
- mov x0, x20 /* Marshal args: - phys_offset */
- mov x1, x21 /* - FDT */
- b start_xen /* and disappear into the land of C */
-1:
- b start_secondary /* (to the appropriate entry point) */
+ ldr x4, =init_data
why not use x3 instead of x4?
I think a remnant of early rework when start_secondary was taking 3
parameters. I will update it.
+ add x4, x4, #INITINFO_stack /* Find the boot-time stack */
+ ldr x4, [x4]
+ add x4, x4, #STACK_SIZE /* (which grows down from the top). */
If you are going to respin it, could you please align the comments a bit
better (one space to the right)?
Sure.
+ sub x4, x4, #CPUINFO_sizeof /* Make room for CPU save record */
+ mov sp, x4
+
+ /* Jump to C world */
+ br x2
ENDPROC(launch)
/* Fail-stop */
Cheers,
--
Julien Grall
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel
|
