Hi Henry,
On 14/08/2023 05:25, Henry Wang wrote:
From: Wei Chen <wei.c...@arm.com>
At the moment, on MMU system, enable_mmu() will return to an
address in the 1:1 mapping, then each path is responsible to
switch to virtual runtime mapping. Then remove_identity_mapping()
is called on the boot CPU to remove all 1:1 mapping.
Since remove_identity_mapping() is not necessary on Non-MMU system,
and we also avoid creating empty function for Non-MMU system, trying
to keep only one codeflow in arm64/head.S, we move path switch and
remove_identity_mapping() in enable_mmu() on MMU system.
As the remove_identity_mapping should only be called for the boot
CPU only, so we introduce enable_boot_cpu_mm() for boot CPU and
enable_secondary_cpu_mm() for secondary CPUs in this patch.
Signed-off-by: Wei Chen <wei.c...@arm.com>
Signed-off-by: Penny Zheng <penny.zh...@arm.com> > Signed-off-by: Henry Wang
<henry.w...@arm.com>
One remark below. With or without it addressed:
Reviewed-by: Julien Grall <jgr...@amazon.com>
[...]
+/*
+ * Enable mm (turn on the data cache and the MMU) for secondary CPUs.
+ * The function will return to the virtual address provided in LR (e.g. the
+ * runtime mapping).
+ *
+ * Inputs:
+ * lr : Virtual address to return to.
+ *
+ * Clobbers x0 - x5
+ */
+enable_secondary_cpu_mm:
+ mov x5, lr
+
+ load_paddr x0, init_ttbr
+ ldr x0, [x0]
+
+ bl enable_mmu
+ mov lr, x5
+
+ /* Return to the virtual address requested by the caller. */
+ ret
+ENDPROC(enable_secondary_cpu_mm)
NIT: enable_mmu() could directly return to the virtual address. This
would reduce the function to:
load_paddr x0, init_ttbr
ldr x0, [x0]
/* Return to the virtual address requested by the caller.
b enable_mmu
+
+/*
+ * Enable mm (turn on the data cache and the MMU) for the boot CPU.
+ * The function will return to the virtual address provided in LR (e.g. the
+ * runtime mapping).
+ *
+ * Inputs:
+ * lr : Virtual address to return to.
+ *
+ * Clobbers x0 - x5
+ */
+enable_boot_cpu_mm:
+ mov x5, lr
+
+ bl create_page_tables
+ load_paddr x0, boot_pgtable
+
+ bl enable_mmu
+
+ /*
+ * The MMU is turned on and we are in the 1:1 mapping. Switch
+ * to the runtime mapping.
+ */
+ ldr x0, =1f
+ br x0
+1:
+ mov lr, x5
+ /*
+ * The 1:1 map may clash with other parts of the Xen virtual memory
+ * layout. As it is not used anymore, remove it completely to avoid
+ * having to worry about replacing existing mapping afterwards.
+ * Function will return to the virtual address requested by the caller.
+ */
+ b remove_identity_mapping
+ENDPROC(enable_boot_cpu_mm)
+
/*
* Remove the 1:1 map from the page-tables. It is not easy to keep track
* where the 1:1 map was mapped, so we will look for the top-level entry
Cheers,
--
Julien Grall
