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Re: [Minios-devel] [PATCH 03/40] arm64: add the boot code



Hi Shijie,

More question about the boot code...

On 03/11/17 03:11, Huang Shijie wrote:
+ENTRY(_start)
+    /* Save the FDT pointer */
+    mov     x20, x0
+
+    /* Calculate where we are */
+    bl      _calc_offset
+
+    PRINT("- Mini-OS booting -\n")
+
+    PRINT("- Setup CPU -\n")
+    /* Setup CPU for turning on the MMU. */
+    bl      _setup_cpu
+
+    PRINT("- Setup booting pagetable -\n")
+    /* Setup the initial page table. */
+    bl      _setup_initial_pgtable
+
+    /* Setup the identity mapping */
+    bl      _setup_idmap_pgtable
+
+    /* Load TTBRx */
+    msr     ttbr1_el1, x4
+    msr     ttbr0_el1, x5

First at all, this is not entirely obvious where x4 and x5 are been set. Proper documentation would be needed for that.

Now, IIUC the code TTBR0_EL1 will contain the identity mappings. I was expecting to see it removed as soon as MMU is enabled. But this does not seem to be the case. Why?

Cheers,

--
Julien Grall

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