[Xen-devel] [PATCH] xen/arm: mm: optimize setup_pagetables

[Peng Fan <van.freenix@xxxxxxxxx>]

Before relocating xen to high address, need to build
the mapping BOOT_RELOC_VIRT_START to xen_paddr into
boot_pgtable and xen_pgtable.

In setup_pagetables, relocate_xen will switch the root
page table from boot_pgtable to xen_pgtable/cpu0_pgtable.

Before relocate_xen:
If touching xen_pgtable, no need to flush_xen_data_tlb_range_va_local.
We only need to flush tlb when touch boot_pgtable.
And no need to use write_pte for xen_pgtable, we can simply use
"xen_second[second_table_offset(dest_va)] = pte;"

Also move the piece code near DTB/Fixmap/XEN_VIRT_START to
be more easier to understand.

Signed-off-by: Peng Fan <van.freenix@xxxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxx>
---

There is no function change in this patch, I just think
there is no need to use flush_xen_data_tlb_range_va_local and write_pte
at that point. And I tested this patch on AArch64.

 xen/arch/arm/mm.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 94ea054..bebd82f 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -443,12 +443,6 @@ void __init setup_pagetables(unsigned long 
boot_phys_offset, paddr_t xen_paddr)
     lpae_t pte, *p;
     int i;
 
-    /* Map the destination in the boot misc area. */
-    dest_va = BOOT_RELOC_VIRT_START;
-    pte = mfn_to_xen_entry(xen_paddr >> PAGE_SHIFT, WRITEALLOC);
-    write_pte(xen_second + second_table_offset(dest_va), pte);
-    flush_xen_data_tlb_range_va_local(dest_va, SECOND_SIZE);
-
     /* Calculate virt-to-phys offset for the new location */
     phys_offset = xen_paddr - (unsigned long) _start;
 
@@ -498,6 +492,11 @@ void __init setup_pagetables(unsigned long 
boot_phys_offset, paddr_t xen_paddr)
     /* Map the destination in the boot misc area. */
     dest_va = BOOT_RELOC_VIRT_START;
     pte = mfn_to_xen_entry(xen_paddr >> PAGE_SHIFT, WRITEALLOC);
+    xen_second[second_table_offset(dest_va)] = pte;
+
+    /* Map the destination in the boot misc area. */
+    dest_va = BOOT_RELOC_VIRT_START;
+    pte = mfn_to_xen_entry(xen_paddr >> PAGE_SHIFT, WRITEALLOC);
     write_pte(boot_second + second_table_offset(dest_va), pte);
     flush_xen_data_tlb_range_va_local(dest_va, SECOND_SIZE);
 #ifdef CONFIG_ARM_64
-- 
2.6.2


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