[Xen-devel] [PATCH v3 19/28] xen/arm32: head: Don't setup the fixmap on secondary CPUs

[Julien Grall <julien.grall@xxxxxxx>]

setup_fixmap() will setup the fixmap in the boot page tables in order to
use earlyprintk and also update the register r11 holding the address to
the UART.

However, secondary CPUs are not using earlyprintk between turning the
MMU on and switching to the runtime page table. So setting up the
fixmap in the boot pages table is pointless.

This means most of setup_fixmap() is not necessary for the secondary
CPUs. The update of UART address is now moved out of setup_fixmap() and
duplicated in the CPU boot and secondary CPUs boot. Additionally, the
call to setup_fixmap() is removed from secondary CPUs boot.

Lastly, take the opportunity to replace load from literal pool with the
new macro mov_w.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

---
    Changes in v3:
        - Add Stefano's reviewed-by

    Changes in v2:
        - Patch added
---
 xen/arch/arm/arm32/head.S | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
index 0c95d1c432..8f945d318a 100644
--- a/xen/arch/arm/arm32/head.S
+++ b/xen/arch/arm/arm32/head.S
@@ -159,6 +159,10 @@ past_zImage:
         mov   pc, r0
 primary_switched:
         bl    setup_fixmap
+#ifdef CONFIG_EARLY_PRINTK
+        /* Use a virtual address to access the UART. */
+        mov_w r11, EARLY_UART_VIRTUAL_ADDRESS
+#endif
         b     launch
 ENDPROC(start)
 
@@ -201,8 +205,6 @@ GLOBAL(init_secondary)
         ldr   r0, =secondary_switched
         mov   pc, r0
 secondary_switched:
-        bl    setup_fixmap
-
         /*
          * Non-boot CPUs need to move on to the proper pagetables, which were
          * setup in init_secondary_pagetables.
@@ -221,6 +223,10 @@ secondary_switched:
         dsb                          /* Ensure completion of TLB+BP flush */
         isb
 
+#ifdef CONFIG_EARLY_PRINTK
+        /* Use a virtual address to access the UART. */
+        mov_w r11, EARLY_UART_VIRTUAL_ADDRESS
+#endif
         b     launch
 ENDPROC(init_secondary)
 
@@ -475,13 +481,6 @@ setup_fixmap:
          */
         dsb
 #if defined(CONFIG_EARLY_PRINTK) /* Fixmap is only used by early printk */
-        /*
-         * Non-boot CPUs don't need to rebuild the fixmap itself, just
-         * the mapping from boot_second to xen_fixmap
-         */
-        teq   r12, #0
-        bne   1f
-
         /* Add UART to the fixmap table */
         ldr   r1, =xen_fixmap        /* r1 := vaddr (xen_fixmap) */
         lsr   r2, r11, #THIRD_SHIFT
@@ -502,9 +501,6 @@ setup_fixmap:
         mov   r4, r4, lsr #(SECOND_SHIFT - 3)   /* r4 := Slot for FIXMAP(0) */
         mov   r3, #0x0
         strd  r2, r3, [r1, r4]       /* Map it in the fixmap's slot */
-
-        /* Use a virtual address to access the UART. */
-        ldr   r11, =EARLY_UART_VIRTUAL_ADDRESS
 #endif
 
         /*
-- 
2.11.0


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