[Xen-devel] [PATCH v2 13/35] xen/arm64: 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 x23 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.

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

---
    Changes in v2:
        - Fix typo
        - Clarify the commit message
        - Add Stefano's reviewed-by
---
 xen/arch/arm/arm64/head.S | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index 4ce4895a0d..28efe9230c 100644
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -301,6 +301,10 @@ real_start_efi:
         br    x0
 primary_switched:
         bl    setup_fixmap
+#ifdef CONFIG_EARLY_PRINTK
+        /* Use a virtual address to access the UART. */
+        ldr   x23, =EARLY_UART_VIRTUAL_ADDRESS
+#endif
         b     launch
 ENDPROC(real_start)
 
@@ -343,8 +347,6 @@ GLOBAL(init_secondary)
         ldr   x0, =secondary_switched
         br    x0
 secondary_switched:
-        bl    setup_fixmap
-
         /*
          * Non-boot CPUs need to move on to the proper pagetables, which were
          * setup in init_secondary_pagetables.
@@ -361,6 +363,10 @@ secondary_switched:
         dsb   sy                     /* Ensure completion of TLB flush */
         isb
 
+#ifdef CONFIG_EARLY_PRINTK
+        /* Use a virtual address to access the UART. */
+        ldr   x23, =EARLY_UART_VIRTUAL_ADDRESS
+#endif
         b     launch
 ENDPROC(init_secondary)
 
@@ -624,10 +630,6 @@ setup_fixmap:
          * don't need the 1:1 map any more */
         dsb   sy
 #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 */
-        cbnz  x22, 1f
-
         /* Add UART to the fixmap table */
         ldr   x1, =xen_fixmap        /* x1 := vaddr (xen_fixmap) */
         lsr   x2, x23, #THIRD_SHIFT
@@ -635,7 +637,6 @@ setup_fixmap:
         mov   x3, #PT_DEV_L3
         orr   x2, x2, x3             /* x2 := 4K dev map including UART */
         str   x2, [x1, #(FIXMAP_CONSOLE*8)] /* Map it in the first fixmap's 
slot */
-1:
 
         /* Map fixmap into boot_second */
         ldr   x4, =boot_second       /* x4 := vaddr (boot_second) */
@@ -645,9 +646,6 @@ setup_fixmap:
         ldr   x1, =FIXMAP_ADDR(0)
         lsr   x1, x1, #(SECOND_SHIFT - 3)   /* x1 := Slot for FIXMAP(0) */
         str   x2, [x4, x1]           /* Map it in the fixmap's slot */
-
-        /* Use a virtual address to access the UART. */
-        ldr   x23, =EARLY_UART_VIRTUAL_ADDRESS
 #endif
 
         /*
-- 
2.11.0


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