[Xen-devel] [PATCH v3 25/28] xen/arm64: head: Introduce macros to create table and mapping entry

[Julien Grall <julien.grall@arm.com>]

At the moment, any update to the boot-pages are open-coded. This is
making more difficult to understand the logic of a function as each
update roughly requires 6 instructions.

To ease the readability, two new macros are introduced:
    - create_table_entry: Create a page-table entry in a given table.
    This can work at any level.
    - create_mapping_entry: Create a mapping entry in a given table.
    None of the users will require to map at any other level than 3rd
    (i.e page granularity). So the macro is supporting support 3rd level
    mapping.

Furthermore, the two macros are capable to work independently of the
state of the MMU.

Lastly, take the opportunity to replace open-coded version in
setup_fixmap() by the two new macros. The ones in create_page_tables()
will be replaced in a follow-up patch.

Signed-off-by: Julien Grall <julien.grall@arm.com>

---
    Changes in v3:
        - Patch added
---
 xen/arch/arm/arm64/head.S | 83 ++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 67 insertions(+), 16 deletions(-)

diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index f2a0e1d3b0..f4177dbba1 100644
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -492,6 +492,68 @@ cpu_init:
 ENDPROC(cpu_init)
 
 /*
+ * Macro to create a page table entry in \ptbl to \tbl
+ *
+ * ptbl:    table symbol where the entry will be created
+ * tbl:     table symbol to point to
+ * virt:    virtual address
+ * shift:   #imm page table shift
+ * tmp1:    scratch register
+ * tmp2:    scratch register
+ * tmp3:    scratch register
+ *
+ * Preserves \virt
+ * Clobbers \tmp1, \tmp2, \tmp3
+ *
+ * Also use x20 for the phys offset.
+ *
+ * Note that all parameters using registers should be distinct.
+ */
+.macro create_table_entry, ptbl, tbl, virt, shift, tmp1, tmp2, tmp3
+        lsr   \tmp1, \virt, #\shift
+        and   \tmp1, \tmp1, #LPAE_ENTRY_MASK/* \tmp1 := slot in \tlb */
+
+        load_paddr \tmp2, \tbl
+        mov   \tmp3, #PT_PT                 /* \tmp3 := right for linear PT */
+        orr   \tmp3, \tmp3, \tmp2           /*          + \tlb paddr */
+
+        adr_l \tmp2, \ptbl
+
+        str   \tmp3, [\tmp2, \tmp1, lsl #3]
+.endm
+
+/*
+ * Macro to create a mapping entry in \tbl to \phys. Only mapping in 3rd
+ * level table (i.e page granularity) is supported.
+ *
+ * tbl:     table symbol where the entry will be created
+ * virt:    virtual address
+ * phys:    physical address (should be page aligned)
+ * tmp1:    scratch register
+ * tmp2:    scratch register
+ * tmp3:    scratch register
+ * type:    mapping type. If not specified it will be normal memory (PT_MEM_L3)
+ *
+ * Preserves \virt, \phys
+ * Clobbers \tmp1, \tmp2, \tmp3
+ *
+ * Note that all parameters using registers should be distinct.
+ */
+.macro create_mapping_entry, tbl, virt, phys, tmp1, tmp2, tmp3, type=PT_MEM_L3
+        and   \tmp3, \phys, #THIRD_MASK     /* \tmp3 := PAGE_ALIGNED(phys) */
+
+        lsr   \tmp1, \virt, #THIRD_SHIFT
+        and   \tmp1, \tmp1, #LPAE_ENTRY_MASK/* \tmp1 := slot in \tlb */
+
+        mov   \tmp2, #\type                 /* \tmp2 := right for section PT */
+        orr   \tmp2, \tmp2, \tmp3           /*          + PAGE_ALIGNED(phys) */
+
+        adr_l \tmp3, \tbl
+
+        str   \tmp2, [\tmp3, \tmp1, lsl #3]
+.endm
+
+/*
  * Rebuild the boot pagetable's first-level entries. The structure
  * is described in mm.c.
  *
@@ -735,28 +797,17 @@ ENDPROC(remove_identity_mapping)
  *   x20: Physical offset
  *   x23: Early UART base physical address
  *
- * Clobbers x1 - x4
+ * Clobbers x0 - x3
  */
 setup_fixmap:
 #ifdef CONFIG_EARLY_PRINTK
         /* Add UART to the fixmap table */
-        ldr   x1, =xen_fixmap        /* x1 := vaddr (xen_fixmap) */
-        lsr   x2, x23, #THIRD_SHIFT
-        lsl   x2, x2, #THIRD_SHIFT   /* 4K aligned paddr of UART */
-        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 */
+        ldr   x0, =EARLY_UART_VIRTUAL_ADDRESS
+        create_mapping_entry xen_fixmap, x0, x23, x1, x2, x3, type=PT_DEV_L3
 #endif
-
         /* Map fixmap into boot_second */
-        ldr   x4, =boot_second       /* x4 := vaddr (boot_second) */
-        load_paddr x2, xen_fixmap
-        mov   x3, #PT_PT
-        orr   x2, x2, x3             /* x2 := table map of xen_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 */
-
+        ldr   x0, =FIXMAP_ADDR(0)
+        create_table_entry boot_second, xen_fixmap, x0, SECOND_SHIFT, x1, x2, x3
         /* Ensure any page table updates made above have occurred. */
         dsb   nshst
 
-- 
2.11.0


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