Hi Peng,
I would rename the title: "xen/arm: mm: remove unnecessary tlb flush in
setup_pagetables".
On 11/05/2016 08:59, Peng Fan wrote:
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.
The commit message is rather hard to understand. Can you please rework
it say:
- CPU0 is using the boot pages table and xen_second is not part of
them => No need to flush the TLB
- Clean up the code (i.e the code movement)
However, I would prefer to see 2 patches, one for removing the tlb
flush, the other to move the code.
[...]
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);
Why do you need to recompute "pte" and "dest_va"? They will be the same
for "boot_second" and "xen_second".
Also, I think the code is still confusing in the current state because
of the comments "Map the destination in the boot misc area.". They need
to be updated to differentiate xen_second vs boot_second.
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
Regards,
--
Julien Grall
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel