[PATCH V2 1/2] xen/arm: mm: remove unnecessary tlb flush in setup_pagetables

[PATCH V2 1/2] xen/arm: mm: remove unnecessary tlb flush in setup_pagetables

[Peng Fan]

CPU0 is using the boot pages table before relocating xen and
xen_second is not part of them. So, no need to flush the TLB
when filling xen_second.

Signed-off-by: Peng Fan <van.freenix@gmail.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Julien Grall <julien.grall@arm.com>
---

V2:
 Following Julien's comments:
   split the V1 patch into two patches. This patch only remove tlb flush.
   refine commit log

 xen/arch/arm/mm.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 94ea054..addd699 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -447,7 +447,6 @@ void __init setup_pagetables(unsigned long boot_phys_offset, paddr_t xen_paddr)
     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;
-- 
2.6.2


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[PATCH V2 2/2] xen/arm: mm: clean up code in setup_pagetables

[Peng Fan]

In setup_pagetables, need to map BOOT_RELOC_VIRT_START
in xen_second and boot_second, so we can merge the two
pieces code into one code block.

Also no need to use write_pte when map BOOT_RELOC_VIRT_START
in xen_second, because CPU0 is using boot page tables now.

Signed-off-by: Peng Fan <van.freenix@gmail.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Julien Grall <julien.grall@arm.com>
---

V2:
 Follow Julien's comments:
   split the V1 patch into two patches, this patch is the code movement part.

 xen/arch/arm/mm.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index addd699..0a4f845 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -443,11 +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);
-
     /* Calculate virt-to-phys offset for the new location */
     phys_offset = xen_paddr - (unsigned long) _start;
 
@@ -494,9 +489,12 @@ void __init setup_pagetables(unsigned long boot_phys_offset, paddr_t xen_paddr)
     pte = boot_second[second_table_offset(BOOT_FDT_VIRT_START)];
     xen_second[second_table_offset(BOOT_FDT_VIRT_START)] = pte;
 
-    /* Map the destination in the boot misc area. */
+    /* ... Boot Misc area for xen relocation */
     dest_va = BOOT_RELOC_VIRT_START;
     pte = mfn_to_xen_entry(xen_paddr >> PAGE_SHIFT, WRITEALLOC);
+    /* Map the destination in xen_second. */
+    xen_second[second_table_offset(dest_va)] = pte;
+    /* Map the destination in 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
-- 
2.6.2


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Re: [PATCH V2 1/2] xen/arm: mm: remove unnecessary tlb flush in setup_pagetables

[Julien Grall]

Hi Peng,

On 12/05/16 03:01, Peng Fan wrote:
> CPU0 is using the boot pages table before relocating xen and
> xen_second is not part of them. So, no need to flush the TLB
> when filling xen_second.
>
> Signed-off-by: Peng Fan <van.freenix@gmail.com>
> Cc: Stefano Stabellini <sstabellini@kernel.org>
> Cc: Julien Grall <julien.grall@arm.com>

This will be Xen 4.8 material:

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

Regards,

-- 
Julien Grall

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Re: [PATCH V2 2/2] xen/arm: mm: clean up code in setup_pagetables

[Julien Grall]

Hi Peng,

Hi Peng,

On 12/05/16 03:01, Peng Fan wrote:
> In setup_pagetables, need to map BOOT_RELOC_VIRT_START
> in xen_second and boot_second, so we can merge the two
> pieces code into one code block.

There is a missing subject for "need". I would say:

"The base of address for the relocated xen needs to be mapped at the 
same virtual address (BOOT_RELOC_VIRT_START) in both the boot and 
runtime page tables. So we can merge the two pieces of code into on code 
block."

>
> Also no need to use write_pte when map BOOT_RELOC_VIRT_START
> in xen_second, because CPU0 is using boot page tables now.
>
> Signed-off-by: Peng Fan <van.freenix@gmail.com>
> Cc: Stefano Stabellini <sstabellini@kernel.org>
> Cc: Julien Grall <julien.grall@arm.com>
> ---
>
> V2:
>   Follow Julien's comments:
>     split the V1 patch into two patches, this patch is the code movement part.
>
>   xen/arch/arm/mm.c | 10 ++++------
>   1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> index addd699..0a4f845 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -443,11 +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);
> -
>       /* Calculate virt-to-phys offset for the new location */
>       phys_offset = xen_paddr - (unsigned long) _start;
>
> @@ -494,9 +489,12 @@ void __init setup_pagetables(unsigned long boot_phys_offset, paddr_t xen_paddr)
>       pte = boot_second[second_table_offset(BOOT_FDT_VIRT_START)];
>       xen_second[second_table_offset(BOOT_FDT_VIRT_START)] = pte;
>
> -    /* Map the destination in the boot misc area. */
> +    /* ... Boot Misc area for xen relocation */
>       dest_va = BOOT_RELOC_VIRT_START;
>       pte = mfn_to_xen_entry(xen_paddr >> PAGE_SHIFT, WRITEALLOC);
> +    /* Map the destination in xen_second. */
> +    xen_second[second_table_offset(dest_va)] = pte;
> +    /* Map the destination in 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

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