[PATCH 0/7] xen/arm: More clean-ups and improvement

[PATCH 0/7] xen/arm: More clean-ups and improvement

[Julien Grall]

From: Julien Grall <jgrall@amazon.com>

Hi all,

This is another collection of patches that I accumulated while
reworking the boot code. I am not planning to target Xen 4.17
for the boot code (still working on it and it is risky). But I
the clean-ups and improvement patches could be.

Cheers,

Julien Grall (7):
  xen/arm64: head: Don't set x22 and update the documentation
  xen/arm64: head: Introduce get_table_slot() and use it
  xen/arm32: head: Introduce get_table_slot() and use it
  xen/arm32: heap: Rework adr_l so it doesn't rely on where Xen is
    loaded
  xen/arm32: head: Move earlyprintk messages to .rodata.str
  xen/arm: Tweak the dump page-table walk output
  xen/arm32: traps: Dump more information for hypervisor data abort

 xen/arch/arm/arm32/head.S        | 102 +++++++++++++++----------------
 xen/arch/arm/arm32/traps.c       |   2 +-
 xen/arch/arm/arm64/head.S        |  61 +++++++++---------
 xen/arch/arm/include/asm/traps.h |   1 +
 xen/arch/arm/mm.c                |   2 +-
 5 files changed, 83 insertions(+), 85 deletions(-)

-- 
2.37.1

[PATCH 1/7] xen/arm64: head: Don't set x22 and update the documentation

[Julien Grall]

From: Julien Grall <jgrall@amazon.com>

Since commit 7e14a47e7c73 ("xen/arm64: head Rework and document
launch()"), the boot code is setting x22 but not read it.

So remove the two instructions setting x22 and update the documentation
to show x22 has no specific purpose.

Signed-off-by: Julien Grall <jgrall@amazon.com>
---
 xen/arch/arm/arm64/head.S | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index 1babcc65d7c9..26cc7705f556 100644
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -71,7 +71,7 @@
  *  x19 - paddr(start)
  *  x20 - phys offset
  *  x21 - DTB address (boot cpu only)
- *  x22 - is_secondary_cpu
+ *  x22 -
  *  x23 - UART address
  *  x24 -
  *  x25 -
@@ -305,8 +305,6 @@ real_start_efi:
 #endif
         PRINT("- Boot CPU booting -\r\n")
 
-        mov   x22, #0                /* x22 := is_secondary_cpu */
-
         bl    check_cpu_mode
         bl    cpu_init
         bl    create_page_tables
@@ -345,8 +343,6 @@ GLOBAL(init_secondary)
         adr   x19, start             /* x19 := paddr (start) */
         sub   x20, x19, x0           /* x20 := phys-offset */
 
-        mov   x22, #1                /* x22 := is_secondary_cpu */
-
         mrs   x0, mpidr_el1
         ldr   x13, =(~MPIDR_HWID_MASK)
         bic   x24, x0, x13           /* Mask out flags to get CPU ID */
-- 
2.37.1

RE: [PATCH 1/7] xen/arm64: head: Don't set x22 and update the documentation

[Wei Chen]

Hi Julien,

> -----Original Message-----
> From: Xen-devel <xen-devel-bounces@lists.xenproject.org> On Behalf Of
> Julien Grall
> Sent: 2022年8月13日 3:25
> To: xen-devel@lists.xenproject.org
> Cc: julien@xen.org; Julien Grall <jgrall@amazon.com>; Stefano Stabellini
> <sstabellini@kernel.org>; Bertrand Marquis <Bertrand.Marquis@arm.com>;
> Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
> Subject: [PATCH 1/7] xen/arm64: head: Don't set x22 and update the
> documentation
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> Since commit 7e14a47e7c73 ("xen/arm64: head Rework and document
> launch()"), the boot code is setting x22 but not read it.
> 
> So remove the two instructions setting x22 and update the documentation
> to show x22 has no specific purpose.
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
> ---
>  xen/arch/arm/arm64/head.S | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
> index 1babcc65d7c9..26cc7705f556 100644
> --- a/xen/arch/arm/arm64/head.S
> +++ b/xen/arch/arm/arm64/head.S
> @@ -71,7 +71,7 @@
>   *  x19 - paddr(start)
>   *  x20 - phys offset
>   *  x21 - DTB address (boot cpu only)
> - *  x22 - is_secondary_cpu
> + *  x22 -
>   *  x23 - UART address
>   *  x24 -
>   *  x25 -
> @@ -305,8 +305,6 @@ real_start_efi:
>  #endif
>          PRINT("- Boot CPU booting -\r\n")
> 
> -        mov   x22, #0                /* x22 := is_secondary_cpu */
> -
>          bl    check_cpu_mode
>          bl    cpu_init
>          bl    create_page_tables
> @@ -345,8 +343,6 @@ GLOBAL(init_secondary)
>          adr   x19, start             /* x19 := paddr (start) */
>          sub   x20, x19, x0           /* x20 := phys-offset */
> 
> -        mov   x22, #1                /* x22 := is_secondary_cpu */
> -
>          mrs   x0, mpidr_el1
>          ldr   x13, =(~MPIDR_HWID_MASK)
>          bic   x24, x0, x13           /* Mask out flags to get CPU ID */
> --
> 2.37.1
> 

Reviewed-by: Wei Chen <Wei.Chen@arm.com>

Re: [PATCH 1/7] xen/arm64: head: Don't set x22 and update the documentation

[Bertrand Marquis]

Hi Julien,

> On 12 Aug 2022, at 20:24, Julien Grall <julien@xen.org> wrote:
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> Since commit 7e14a47e7c73 ("xen/arm64: head Rework and document
> launch()"), the boot code is setting x22 but not read it.
> 
> So remove the two instructions setting x22 and update the documentation
> to show x22 has no specific purpose.
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

Cheers
Bertrand
> ---
> xen/arch/arm/arm64/head.S | 6 +-----
> 1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
> index 1babcc65d7c9..26cc7705f556 100644
> --- a/xen/arch/arm/arm64/head.S
> +++ b/xen/arch/arm/arm64/head.S
> @@ -71,7 +71,7 @@
>  *  x19 - paddr(start)
>  *  x20 - phys offset
>  *  x21 - DTB address (boot cpu only)
> - *  x22 - is_secondary_cpu
> + *  x22 -
>  *  x23 - UART address
>  *  x24 -
>  *  x25 -
> @@ -305,8 +305,6 @@ real_start_efi:
> #endif
>         PRINT("- Boot CPU booting -\r\n")
> 
> -        mov   x22, #0                /* x22 := is_secondary_cpu */
> -
>         bl    check_cpu_mode
>         bl    cpu_init
>         bl    create_page_tables
> @@ -345,8 +343,6 @@ GLOBAL(init_secondary)
>         adr   x19, start             /* x19 := paddr (start) */
>         sub   x20, x19, x0           /* x20 := phys-offset */
> 
> -        mov   x22, #1                /* x22 := is_secondary_cpu */
> -
>         mrs   x0, mpidr_el1
>         ldr   x13, =(~MPIDR_HWID_MASK)
>         bic   x24, x0, x13           /* Mask out flags to get CPU ID */
> -- 
> 2.37.1
> 

[PATCH 2/7] xen/arm64: head: Introduce get_table_slot() and use it

[Julien Grall]

From: Julien Grall <jgrall@amazon.com>

There are a few places in the code that need to find the slot
at a given page-table level.

So create a new macro get_table_slot() for that. This will reduce
the effort to figure out whether the code is doing the right thing.

Take the opportunity to use 'ubfx'. The only benefits is reducing
the number of instructions from 2 to 1.

The new macro is used everywhere we need to compute the slot. This
requires to tweak the parameter of create_table_entry() to pass
a level rather than shift.

Note, for slot 0 the code is currently skipping the masking part. While
this is fine, it is safer to mask it as technically slot 0 only covers
bit 48 - 39 bit (assuming 4KB page granularity).

Take the opportunity to correct the comment when finding the second
slot for the identity mapping (we are computing the second slot
rather than first).

Signed-off-by: Julien Grall <jgrall@amazon.com>

----

    This patch also has the benefits to reduce the number
    of use of {ZEROETH, FIRST, SECOND, THIRD}_SHIFT. The next
    patch for arm32 will reduce further.
---
 xen/arch/arm/arm64/head.S | 55 +++++++++++++++++++++------------------
 1 file changed, 30 insertions(+), 25 deletions(-)

diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index 26cc7705f556..ad014716db6f 100644
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -493,13 +493,24 @@ cpu_init:
         ret
 ENDPROC(cpu_init)
 
+/*
+ * Macro to find the slot number at a given page-table level
+ *
+ * slot:     slot computed
+ * virt:     virtual address
+ * lvl:      page-table level
+ */
+.macro get_table_slot, slot, virt, lvl
+        ubfx  \slot, \virt, #XEN_PT_LEVEL_SHIFT(\lvl), #XEN_PT_LPAE_SHIFT
+.endm
+
 /*
  * 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
+ * lvl:     page-table level
  * tmp1:    scratch register
  * tmp2:    scratch register
  * tmp3:    scratch register
@@ -511,9 +522,8 @@ ENDPROC(cpu_init)
  *
  * 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, #XEN_PT_LPAE_ENTRY_MASK/* \tmp1 := slot in \tlb */
+.macro create_table_entry, ptbl, tbl, virt, lvl, tmp1, tmp2, tmp3
+        get_table_slot \tmp1, \virt, \lvl   /* \tmp1 := slot in \tlb */
 
         load_paddr \tmp2, \tbl
         mov   \tmp3, #PT_PT                 /* \tmp3 := right for linear PT */
@@ -544,8 +554,7 @@ ENDPROC(cpu_init)
 .macro create_mapping_entry, ptbl, 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, #XEN_PT_LPAE_ENTRY_MASK/* \tmp1 := slot in \tlb */
+        get_table_slot \tmp1, \virt, 3      /* \tmp1 := slot in \tlb */
 
         mov   \tmp2, #\type                 /* \tmp2 := right for section PT */
         orr   \tmp2, \tmp2, \tmp3           /*          + PAGE_ALIGNED(phys) */
@@ -573,9 +582,9 @@ ENDPROC(cpu_init)
 create_page_tables:
         /* Prepare the page-tables for mapping Xen */
         ldr   x0, =XEN_VIRT_START
-        create_table_entry boot_pgtable, boot_first, x0, ZEROETH_SHIFT, x1, x2, x3
-        create_table_entry boot_first, boot_second, x0, FIRST_SHIFT, x1, x2, x3
-        create_table_entry boot_second, boot_third, x0, SECOND_SHIFT, x1, x2, x3
+        create_table_entry boot_pgtable, boot_first, x0, 0, x1, x2, x3
+        create_table_entry boot_first, boot_second, x0, 1, x1, x2, x3
+        create_table_entry boot_second, boot_third, x0, 2, x1, x2, x3
 
         /* Map Xen */
         adr_l x4, boot_third
@@ -612,10 +621,10 @@ create_page_tables:
          * XEN_ZEROETH_SLOT, then the 1:1 mapping will use its own set of
          * page-tables from the first level.
          */
-        lsr   x0, x19, #ZEROETH_SHIFT   /* x0 := zeroeth slot */
+        get_table_slot x0, x19, 0       /* x0 := zeroeth slot */
         cmp   x0, #XEN_ZEROETH_SLOT
         beq   1f
-        create_table_entry boot_pgtable, boot_first_id, x19, ZEROETH_SHIFT, x0, x1, x2
+        create_table_entry boot_pgtable, boot_first_id, x19, 0, x0, x1, x2
         b     link_from_first_id
 
 1:
@@ -624,11 +633,10 @@ create_page_tables:
          * then the 1:1 mapping will use its own set of page-tables from
          * the second level.
          */
-        lsr   x0, x19, #FIRST_SHIFT
-        and   x0, x0, #XEN_PT_LPAE_ENTRY_MASK  /* x0 := first slot */
+        get_table_slot x0, x19, 1      /* x0 := first slot */
         cmp   x0, #XEN_FIRST_SLOT
         beq   1f
-        create_table_entry boot_first, boot_second_id, x19, FIRST_SHIFT, x0, x1, x2
+        create_table_entry boot_first, boot_second_id, x19, 1, x0, x1, x2
         b     link_from_second_id
 
 1:
@@ -638,17 +646,16 @@ create_page_tables:
          * third level. For slot XEN_SECOND_SLOT, Xen is not yet able to handle
          * it.
          */
-        lsr   x0, x19, #SECOND_SHIFT
-        and   x0, x0, #XEN_PT_LPAE_ENTRY_MASK  /* x0 := first slot */
+        get_table_slot x0, x19, 2     /* x0 := second slot */
         cmp   x0, #XEN_SECOND_SLOT
         beq   virtphys_clash
-        create_table_entry boot_second, boot_third_id, x19, SECOND_SHIFT, x0, x1, x2
+        create_table_entry boot_second, boot_third_id, x19, 2, x0, x1, x2
         b     link_from_third_id
 
 link_from_first_id:
-        create_table_entry boot_first_id, boot_second_id, x19, FIRST_SHIFT, x0, x1, x2
+        create_table_entry boot_first_id, boot_second_id, x19, 1, x0, x1, x2
 link_from_second_id:
-        create_table_entry boot_second_id, boot_third_id, x19, SECOND_SHIFT, x0, x1, x2
+        create_table_entry boot_second_id, boot_third_id, x19, 2, x0, x1, x2
 link_from_third_id:
         create_mapping_entry boot_third_id, x19, x19, x0, x1, x2
         ret
@@ -705,7 +712,7 @@ remove_identity_mapping:
          * Find the zeroeth slot used. Remove the entry from zeroeth
          * table if the slot is not XEN_ZEROETH_SLOT.
          */
-        lsr   x1, x19, #ZEROETH_SHIFT   /* x1 := zeroeth slot */
+        get_table_slot x1, x19, 0       /* x1 := zeroeth slot */
         cmp   x1, #XEN_ZEROETH_SLOT
         beq   1f
         /* It is not in slot XEN_ZEROETH_SLOT, remove the entry. */
@@ -718,8 +725,7 @@ remove_identity_mapping:
          * Find the first slot used. Remove the entry for the first
          * table if the slot is not XEN_FIRST_SLOT.
          */
-        lsr   x1, x19, #FIRST_SHIFT
-        and   x1, x1, #XEN_PT_LPAE_ENTRY_MASK  /* x1 := first slot */
+        get_table_slot x1, x19, 1       /* x1 := first slot */
         cmp   x1, #XEN_FIRST_SLOT
         beq   1f
         /* It is not in slot XEN_FIRST_SLOT, remove the entry. */
@@ -732,8 +738,7 @@ remove_identity_mapping:
          * Find the second slot used. Remove the entry for the first
          * table if the slot is not XEN_SECOND_SLOT.
          */
-        lsr   x1, x19, #SECOND_SHIFT
-        and   x1, x1, #XEN_PT_LPAE_ENTRY_MASK  /* x1 := first slot */
+        get_table_slot x1, x19, 2       /* x1 := second slot */
         cmp   x1, #XEN_SECOND_SLOT
         beq   identity_mapping_removed
         /* It is not in slot 1, remove the entry */
@@ -771,7 +776,7 @@ setup_fixmap:
 #endif
         /* Map fixmap into boot_second */
         ldr   x0, =FIXMAP_ADDR(0)
-        create_table_entry boot_second, xen_fixmap, x0, SECOND_SHIFT, x1, x2, x3
+        create_table_entry boot_second, xen_fixmap, x0, 2, x1, x2, x3
         /* Ensure any page table updates made above have occurred. */
         dsb   nshst
 
-- 
2.37.1

Re: [PATCH 2/7] xen/arm64: head: Introduce get_table_slot() and use it

[Wei Chen]

Hi Julien,

On 2022/8/13 3:24, Julien Grall wrote:
> From: Julien Grall <jgrall@amazon.com>
> 
> There are a few places in the code that need to find the slot
> at a given page-table level.
> 
> So create a new macro get_table_slot() for that. This will reduce
> the effort to figure out whether the code is doing the right thing.
> 
> Take the opportunity to use 'ubfx'. The only benefits is reducing
> the number of instructions from 2 to 1.
> 
> The new macro is used everywhere we need to compute the slot. This
> requires to tweak the parameter of create_table_entry() to pass
> a level rather than shift.
> 
> Note, for slot 0 the code is currently skipping the masking part. While
> this is fine, it is safer to mask it as technically slot 0 only covers
> bit 48 - 39 bit (assuming 4KB page granularity).
> 
> Take the opportunity to correct the comment when finding the second
> slot for the identity mapping (we are computing the second slot
> rather than first).
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
> 
> ----
> 
>      This patch also has the benefits to reduce the number
>      of use of {ZEROETH, FIRST, SECOND, THIRD}_SHIFT. The next
>      patch for arm32 will reduce further.
> ---
>   xen/arch/arm/arm64/head.S | 55 +++++++++++++++++++++------------------
>   1 file changed, 30 insertions(+), 25 deletions(-)
> 
> diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
> index 26cc7705f556..ad014716db6f 100644
> --- a/xen/arch/arm/arm64/head.S
> +++ b/xen/arch/arm/arm64/head.S
> @@ -493,13 +493,24 @@ cpu_init:
>           ret
>   ENDPROC(cpu_init)
>   
> +/*
> + * Macro to find the slot number at a given page-table level
> + *
> + * slot:     slot computed
> + * virt:     virtual address
> + * lvl:      page-table level
> + */
> +.macro get_table_slot, slot, virt, lvl
> +        ubfx  \slot, \virt, #XEN_PT_LEVEL_SHIFT(\lvl), #XEN_PT_LPAE_SHIFT
> +.endm
> +
>   /*
>    * 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
> + * lvl:     page-table level
>    * tmp1:    scratch register
>    * tmp2:    scratch register
>    * tmp3:    scratch register
> @@ -511,9 +522,8 @@ ENDPROC(cpu_init)
>    *
>    * 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, #XEN_PT_LPAE_ENTRY_MASK/* \tmp1 := slot in \tlb */
> +.macro create_table_entry, ptbl, tbl, virt, lvl, tmp1, tmp2, tmp3
> +        get_table_slot \tmp1, \virt, \lvl   /* \tmp1 := slot in \tlb */
>   
>           load_paddr \tmp2, \tbl
>           mov   \tmp3, #PT_PT                 /* \tmp3 := right for linear PT */
> @@ -544,8 +554,7 @@ ENDPROC(cpu_init)
>   .macro create_mapping_entry, ptbl, 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, #XEN_PT_LPAE_ENTRY_MASK/* \tmp1 := slot in \tlb */
> +        get_table_slot \tmp1, \virt, 3      /* \tmp1 := slot in \tlb */
>   
>           mov   \tmp2, #\type                 /* \tmp2 := right for section PT */
>           orr   \tmp2, \tmp2, \tmp3           /*          + PAGE_ALIGNED(phys) */
> @@ -573,9 +582,9 @@ ENDPROC(cpu_init)
>   create_page_tables:
>           /* Prepare the page-tables for mapping Xen */
>           ldr   x0, =XEN_VIRT_START
> -        create_table_entry boot_pgtable, boot_first, x0, ZEROETH_SHIFT, x1, x2, x3
> -        create_table_entry boot_first, boot_second, x0, FIRST_SHIFT, x1, x2, x3
> -        create_table_entry boot_second, boot_third, x0, SECOND_SHIFT, x1, x2, x3
> +        create_table_entry boot_pgtable, boot_first, x0, 0, x1, x2, x3
> +        create_table_entry boot_first, boot_second, x0, 1, x1, x2, x3
> +        create_table_entry boot_second, boot_third, x0, 2, x1, x2, x3
>   
>           /* Map Xen */
>           adr_l x4, boot_third
> @@ -612,10 +621,10 @@ create_page_tables:
>            * XEN_ZEROETH_SLOT, then the 1:1 mapping will use its own set of
>            * page-tables from the first level.
>            */
> -        lsr   x0, x19, #ZEROETH_SHIFT   /* x0 := zeroeth slot */
> +        get_table_slot x0, x19, 0       /* x0 := zeroeth slot */
>           cmp   x0, #XEN_ZEROETH_SLOT
>           beq   1f
> -        create_table_entry boot_pgtable, boot_first_id, x19, ZEROETH_SHIFT, x0, x1, x2
> +        create_table_entry boot_pgtable, boot_first_id, x19, 0, x0, x1, x2
>           b     link_from_first_id
>   
>   1:
> @@ -624,11 +633,10 @@ create_page_tables:
>            * then the 1:1 mapping will use its own set of page-tables from
>            * the second level.
>            */
> -        lsr   x0, x19, #FIRST_SHIFT
> -        and   x0, x0, #XEN_PT_LPAE_ENTRY_MASK  /* x0 := first slot */
> +        get_table_slot x0, x19, 1      /* x0 := first slot */
>           cmp   x0, #XEN_FIRST_SLOT
>           beq   1f
> -        create_table_entry boot_first, boot_second_id, x19, FIRST_SHIFT, x0, x1, x2
> +        create_table_entry boot_first, boot_second_id, x19, 1, x0, x1, x2
>           b     link_from_second_id
>   
>   1:
> @@ -638,17 +646,16 @@ create_page_tables:
>            * third level. For slot XEN_SECOND_SLOT, Xen is not yet able to handle
>            * it.
>            */
> -        lsr   x0, x19, #SECOND_SHIFT
> -        and   x0, x0, #XEN_PT_LPAE_ENTRY_MASK  /* x0 := first slot */
> +        get_table_slot x0, x19, 2     /* x0 := second slot */
>           cmp   x0, #XEN_SECOND_SLOT
>           beq   virtphys_clash
> -        create_table_entry boot_second, boot_third_id, x19, SECOND_SHIFT, x0, x1, x2
> +        create_table_entry boot_second, boot_third_id, x19, 2, x0, x1, x2
>           b     link_from_third_id
>   
>   link_from_first_id:
> -        create_table_entry boot_first_id, boot_second_id, x19, FIRST_SHIFT, x0, x1, x2
> +        create_table_entry boot_first_id, boot_second_id, x19, 1, x0, x1, x2
>   link_from_second_id:
> -        create_table_entry boot_second_id, boot_third_id, x19, SECOND_SHIFT, x0, x1, x2
> +        create_table_entry boot_second_id, boot_third_id, x19, 2, x0, x1, x2
>   link_from_third_id:
>           create_mapping_entry boot_third_id, x19, x19, x0, x1, x2
>           ret
> @@ -705,7 +712,7 @@ remove_identity_mapping:
>            * Find the zeroeth slot used. Remove the entry from zeroeth
>            * table if the slot is not XEN_ZEROETH_SLOT.
>            */
> -        lsr   x1, x19, #ZEROETH_SHIFT   /* x1 := zeroeth slot */
> +        get_table_slot x1, x19, 0       /* x1 := zeroeth slot */
>           cmp   x1, #XEN_ZEROETH_SLOT
>           beq   1f
>           /* It is not in slot XEN_ZEROETH_SLOT, remove the entry. */
> @@ -718,8 +725,7 @@ remove_identity_mapping:
>            * Find the first slot used. Remove the entry for the first
>            * table if the slot is not XEN_FIRST_SLOT.
>            */
> -        lsr   x1, x19, #FIRST_SHIFT
> -        and   x1, x1, #XEN_PT_LPAE_ENTRY_MASK  /* x1 := first slot */
> +        get_table_slot x1, x19, 1       /* x1 := first slot */
>           cmp   x1, #XEN_FIRST_SLOT
>           beq   1f
>           /* It is not in slot XEN_FIRST_SLOT, remove the entry. */
> @@ -732,8 +738,7 @@ remove_identity_mapping:
>            * Find the second slot used. Remove the entry for the first
>            * table if the slot is not XEN_SECOND_SLOT.
>            */
> -        lsr   x1, x19, #SECOND_SHIFT
> -        and   x1, x1, #XEN_PT_LPAE_ENTRY_MASK  /* x1 := first slot */
> +        get_table_slot x1, x19, 2       /* x1 := second slot */
>           cmp   x1, #XEN_SECOND_SLOT
>           beq   identity_mapping_removed
>           /* It is not in slot 1, remove the entry */
> @@ -771,7 +776,7 @@ setup_fixmap:
>   #endif
>           /* Map fixmap into boot_second */
>           ldr   x0, =FIXMAP_ADDR(0)
> -        create_table_entry boot_second, xen_fixmap, x0, SECOND_SHIFT, x1, x2, x3
> +        create_table_entry boot_second, xen_fixmap, x0, 2, x1, x2, x3
>           /* Ensure any page table updates made above have occurred. */
>           dsb   nshst
>   

Reviewed-by: Wei Chen <Wei.Chen@arm.com>

Re: [PATCH 2/7] xen/arm64: head: Introduce get_table_slot() and use it

[Bertrand Marquis]

Hi Julien,

> On 12 Aug 2022, at 20:24, Julien Grall <julien@xen.org> wrote:
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> There are a few places in the code that need to find the slot
> at a given page-table level.
> 
> So create a new macro get_table_slot() for that. This will reduce
> the effort to figure out whether the code is doing the right thing.
> 
> Take the opportunity to use 'ubfx'. The only benefits is reducing
> the number of instructions from 2 to 1.
> 
> The new macro is used everywhere we need to compute the slot. This
> requires to tweak the parameter of create_table_entry() to pass
> a level rather than shift.
> 
> Note, for slot 0 the code is currently skipping the masking part. While
> this is fine, it is safer to mask it as technically slot 0 only covers
> bit 48 - 39 bit (assuming 4KB page granularity).
> 
> Take the opportunity to correct the comment when finding the second
> slot for the identity mapping (we are computing the second slot
> rather than first).
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

> 
> ----
> 
>    This patch also has the benefits to reduce the number
>    of use of {ZEROETH, FIRST, SECOND, THIRD}_SHIFT. The next
>    patch for arm32 will reduce further.
> ---
> xen/arch/arm/arm64/head.S | 55 +++++++++++++++++++++------------------
> 1 file changed, 30 insertions(+), 25 deletions(-)
> 
> diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
> index 26cc7705f556..ad014716db6f 100644
> --- a/xen/arch/arm/arm64/head.S
> +++ b/xen/arch/arm/arm64/head.S
> @@ -493,13 +493,24 @@ cpu_init:
>         ret
> ENDPROC(cpu_init)
> 
> +/*
> + * Macro to find the slot number at a given page-table level
> + *
> + * slot:     slot computed
> + * virt:     virtual address
> + * lvl:      page-table level
> + */
> +.macro get_table_slot, slot, virt, lvl
> +        ubfx  \slot, \virt, #XEN_PT_LEVEL_SHIFT(\lvl), #XEN_PT_LPAE_SHIFT
> +.endm
> +

Crawling through the macros to verify the code was not that easy.
This is not related to this patch but XEN_PT_* macros could really do with more comments.

Cheers
Bertrand

> /*
>  * 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
> + * lvl:     page-table level
>  * tmp1:    scratch register
>  * tmp2:    scratch register
>  * tmp3:    scratch register
> @@ -511,9 +522,8 @@ ENDPROC(cpu_init)
>  *
>  * 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, #XEN_PT_LPAE_ENTRY_MASK/* \tmp1 := slot in \tlb */
> +.macro create_table_entry, ptbl, tbl, virt, lvl, tmp1, tmp2, tmp3
> +        get_table_slot \tmp1, \virt, \lvl   /* \tmp1 := slot in \tlb */
> 
>         load_paddr \tmp2, \tbl
>         mov   \tmp3, #PT_PT                 /* \tmp3 := right for linear PT */
> @@ -544,8 +554,7 @@ ENDPROC(cpu_init)
> .macro create_mapping_entry, ptbl, 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, #XEN_PT_LPAE_ENTRY_MASK/* \tmp1 := slot in \tlb */
> +        get_table_slot \tmp1, \virt, 3      /* \tmp1 := slot in \tlb */
> 
>         mov   \tmp2, #\type                 /* \tmp2 := right for section PT */
>         orr   \tmp2, \tmp2, \tmp3           /*          + PAGE_ALIGNED(phys) */
> @@ -573,9 +582,9 @@ ENDPROC(cpu_init)
> create_page_tables:
>         /* Prepare the page-tables for mapping Xen */
>         ldr   x0, =XEN_VIRT_START
> -        create_table_entry boot_pgtable, boot_first, x0, ZEROETH_SHIFT, x1, x2, x3
> -        create_table_entry boot_first, boot_second, x0, FIRST_SHIFT, x1, x2, x3
> -        create_table_entry boot_second, boot_third, x0, SECOND_SHIFT, x1, x2, x3
> +        create_table_entry boot_pgtable, boot_first, x0, 0, x1, x2, x3
> +        create_table_entry boot_first, boot_second, x0, 1, x1, x2, x3
> +        create_table_entry boot_second, boot_third, x0, 2, x1, x2, x3
> 
>         /* Map Xen */
>         adr_l x4, boot_third
> @@ -612,10 +621,10 @@ create_page_tables:
>          * XEN_ZEROETH_SLOT, then the 1:1 mapping will use its own set of
>          * page-tables from the first level.
>          */
> -        lsr   x0, x19, #ZEROETH_SHIFT   /* x0 := zeroeth slot */
> +        get_table_slot x0, x19, 0       /* x0 := zeroeth slot */
>         cmp   x0, #XEN_ZEROETH_SLOT
>         beq   1f
> -        create_table_entry boot_pgtable, boot_first_id, x19, ZEROETH_SHIFT, x0, x1, x2
> +        create_table_entry boot_pgtable, boot_first_id, x19, 0, x0, x1, x2
>         b     link_from_first_id
> 
> 1:
> @@ -624,11 +633,10 @@ create_page_tables:
>          * then the 1:1 mapping will use its own set of page-tables from
>          * the second level.
>          */
> -        lsr   x0, x19, #FIRST_SHIFT
> -        and   x0, x0, #XEN_PT_LPAE_ENTRY_MASK  /* x0 := first slot */
> +        get_table_slot x0, x19, 1      /* x0 := first slot */
>         cmp   x0, #XEN_FIRST_SLOT
>         beq   1f
> -        create_table_entry boot_first, boot_second_id, x19, FIRST_SHIFT, x0, x1, x2
> +        create_table_entry boot_first, boot_second_id, x19, 1, x0, x1, x2
>         b     link_from_second_id
> 
> 1:
> @@ -638,17 +646,16 @@ create_page_tables:
>          * third level. For slot XEN_SECOND_SLOT, Xen is not yet able to handle
>          * it.
>          */
> -        lsr   x0, x19, #SECOND_SHIFT
> -        and   x0, x0, #XEN_PT_LPAE_ENTRY_MASK  /* x0 := first slot */
> +        get_table_slot x0, x19, 2     /* x0 := second slot */
>         cmp   x0, #XEN_SECOND_SLOT
>         beq   virtphys_clash
> -        create_table_entry boot_second, boot_third_id, x19, SECOND_SHIFT, x0, x1, x2
> +        create_table_entry boot_second, boot_third_id, x19, 2, x0, x1, x2
>         b     link_from_third_id
> 
> link_from_first_id:
> -        create_table_entry boot_first_id, boot_second_id, x19, FIRST_SHIFT, x0, x1, x2
> +        create_table_entry boot_first_id, boot_second_id, x19, 1, x0, x1, x2
> link_from_second_id:
> -        create_table_entry boot_second_id, boot_third_id, x19, SECOND_SHIFT, x0, x1, x2
> +        create_table_entry boot_second_id, boot_third_id, x19, 2, x0, x1, x2
> link_from_third_id:
>         create_mapping_entry boot_third_id, x19, x19, x0, x1, x2
>         ret
> @@ -705,7 +712,7 @@ remove_identity_mapping:
>          * Find the zeroeth slot used. Remove the entry from zeroeth
>          * table if the slot is not XEN_ZEROETH_SLOT.
>          */
> -        lsr   x1, x19, #ZEROETH_SHIFT   /* x1 := zeroeth slot */
> +        get_table_slot x1, x19, 0       /* x1 := zeroeth slot */
>         cmp   x1, #XEN_ZEROETH_SLOT
>         beq   1f
>         /* It is not in slot XEN_ZEROETH_SLOT, remove the entry. */
> @@ -718,8 +725,7 @@ remove_identity_mapping:
>          * Find the first slot used. Remove the entry for the first
>          * table if the slot is not XEN_FIRST_SLOT.
>          */
> -        lsr   x1, x19, #FIRST_SHIFT
> -        and   x1, x1, #XEN_PT_LPAE_ENTRY_MASK  /* x1 := first slot */
> +        get_table_slot x1, x19, 1       /* x1 := first slot */
>         cmp   x1, #XEN_FIRST_SLOT
>         beq   1f
>         /* It is not in slot XEN_FIRST_SLOT, remove the entry. */
> @@ -732,8 +738,7 @@ remove_identity_mapping:
>          * Find the second slot used. Remove the entry for the first
>          * table if the slot is not XEN_SECOND_SLOT.
>          */
> -        lsr   x1, x19, #SECOND_SHIFT
> -        and   x1, x1, #XEN_PT_LPAE_ENTRY_MASK  /* x1 := first slot */
> +        get_table_slot x1, x19, 2       /* x1 := second slot */
>         cmp   x1, #XEN_SECOND_SLOT
>         beq   identity_mapping_removed
>         /* It is not in slot 1, remove the entry */
> @@ -771,7 +776,7 @@ setup_fixmap:
> #endif
>         /* Map fixmap into boot_second */
>         ldr   x0, =FIXMAP_ADDR(0)
> -        create_table_entry boot_second, xen_fixmap, x0, SECOND_SHIFT, x1, x2, x3
> +        create_table_entry boot_second, xen_fixmap, x0, 2, x1, x2, x3
>         /* Ensure any page table updates made above have occurred. */
>         dsb   nshst
> 
> -- 
> 2.37.1
> 

Re: [PATCH 2/7] xen/arm64: head: Introduce get_table_slot() and use it

[Julien Grall]

On 15/08/2022 15:45, Bertrand Marquis wrote:
> Hi Julien,

Hi Bertrand,

>> On 12 Aug 2022, at 20:24, Julien Grall <julien@xen.org> wrote:
>>
>> From: Julien Grall <jgrall@amazon.com>
>>
>> There are a few places in the code that need to find the slot
>> at a given page-table level.
>>
>> So create a new macro get_table_slot() for that. This will reduce
>> the effort to figure out whether the code is doing the right thing.
>>
>> Take the opportunity to use 'ubfx'. The only benefits is reducing
>> the number of instructions from 2 to 1.
>>
>> The new macro is used everywhere we need to compute the slot. This
>> requires to tweak the parameter of create_table_entry() to pass
>> a level rather than shift.
>>
>> Note, for slot 0 the code is currently skipping the masking part. While
>> this is fine, it is safer to mask it as technically slot 0 only covers
>> bit 48 - 39 bit (assuming 4KB page granularity).
>>
>> Take the opportunity to correct the comment when finding the second
>> slot for the identity mapping (we are computing the second slot
>> rather than first).
>>
>> Signed-off-by: Julien Grall <jgrall@amazon.com>
> Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

Thanks!

>>
>> ----
>>
>>     This patch also has the benefits to reduce the number
>>     of use of {ZEROETH, FIRST, SECOND, THIRD}_SHIFT. The next
>>     patch for arm32 will reduce further.
>> ---
>> xen/arch/arm/arm64/head.S | 55 +++++++++++++++++++++------------------
>> 1 file changed, 30 insertions(+), 25 deletions(-)
>>
>> diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
>> index 26cc7705f556..ad014716db6f 100644
>> --- a/xen/arch/arm/arm64/head.S
>> +++ b/xen/arch/arm/arm64/head.S
>> @@ -493,13 +493,24 @@ cpu_init:
>>          ret
>> ENDPROC(cpu_init)
>>
>> +/*
>> + * Macro to find the slot number at a given page-table level
>> + *
>> + * slot:     slot computed
>> + * virt:     virtual address
>> + * lvl:      page-table level
>> + */
>> +.macro get_table_slot, slot, virt, lvl
>> +        ubfx  \slot, \virt, #XEN_PT_LEVEL_SHIFT(\lvl), #XEN_PT_LPAE_SHIFT
>> +.endm
>> +
> 
> Crawling through the macros to verify the code was not that easy.
> This is not related to this patch but XEN_PT_* macros could really do with more comments.

To me, the name of the macros are self-explaining. So I am not entirely 
what to write in the comments. Please suggest.

Cheers,

-- 
Julien Grall

Re: [PATCH 2/7] xen/arm64: head: Introduce get_table_slot() and use it

[Bertrand Marquis]

Hi,

> On 15 Aug 2022, at 17:44, Julien Grall <julien@xen.org> wrote:
> 
> 
> 
> On 15/08/2022 15:45, Bertrand Marquis wrote:
>> Hi Julien,
> 
> Hi Bertrand,
> 
>>> On 12 Aug 2022, at 20:24, Julien Grall <julien@xen.org> wrote:
>>> 
>>> From: Julien Grall <jgrall@amazon.com>
>>> 
>>> There are a few places in the code that need to find the slot
>>> at a given page-table level.
>>> 
>>> So create a new macro get_table_slot() for that. This will reduce
>>> the effort to figure out whether the code is doing the right thing.
>>> 
>>> Take the opportunity to use 'ubfx'. The only benefits is reducing
>>> the number of instructions from 2 to 1.
>>> 
>>> The new macro is used everywhere we need to compute the slot. This
>>> requires to tweak the parameter of create_table_entry() to pass
>>> a level rather than shift.
>>> 
>>> Note, for slot 0 the code is currently skipping the masking part. While
>>> this is fine, it is safer to mask it as technically slot 0 only covers
>>> bit 48 - 39 bit (assuming 4KB page granularity).
>>> 
>>> Take the opportunity to correct the comment when finding the second
>>> slot for the identity mapping (we are computing the second slot
>>> rather than first).
>>> 
>>> Signed-off-by: Julien Grall <jgrall@amazon.com>
>> Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
> 
> Thanks!
> 
>>> 
>>> ----
>>> 
>>>    This patch also has the benefits to reduce the number
>>>    of use of {ZEROETH, FIRST, SECOND, THIRD}_SHIFT. The next
>>>    patch for arm32 will reduce further.
>>> ---
>>> xen/arch/arm/arm64/head.S | 55 +++++++++++++++++++++------------------
>>> 1 file changed, 30 insertions(+), 25 deletions(-)
>>> 
>>> diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
>>> index 26cc7705f556..ad014716db6f 100644
>>> --- a/xen/arch/arm/arm64/head.S
>>> +++ b/xen/arch/arm/arm64/head.S
>>> @@ -493,13 +493,24 @@ cpu_init:
>>>         ret
>>> ENDPROC(cpu_init)
>>> 
>>> +/*
>>> + * Macro to find the slot number at a given page-table level
>>> + *
>>> + * slot:     slot computed
>>> + * virt:     virtual address
>>> + * lvl:      page-table level
>>> + */
>>> +.macro get_table_slot, slot, virt, lvl
>>> +        ubfx  \slot, \virt, #XEN_PT_LEVEL_SHIFT(\lvl), #XEN_PT_LPAE_SHIFT
>>> +.endm
>>> +
>> Crawling through the macros to verify the code was not that easy.
>> This is not related to this patch but XEN_PT_* macros could really do with more comments.
> 
> To me, the name of the macros are self-explaining. So I am not entirely what to write in the comments. Please suggest.

I will add that in my todo list and try to suggest something in the future (this is really not critical).
I was just pointing out because doing a deep review for someone who did not write this is complex due to the macros of macros of macros of macros ...

Cheers
Bertrand

> 
> Cheers,
> 
> -- 
> Julien Grall

[PATCH 3/7] xen/arm32: head: Introduce get_table_slot() and use it

[Julien Grall]

From: Julien Grall <jgrall@amazon.com>

There are a few places in the code that need to find the slot at a
given page-table level.

So create a new macro get_table_slot() for that. This will reduce
the effort to figure out whether the code is doing the right thing.

The new macro is using 'ubfx' (or 'lsr' for the first level) rather
than the existing sequence (mov_w, lsr, and) because it doesn't require
a scratch register and reduce the number of instructions (4 -> 1).

Signed-off-by: Julien Grall <jgrall@amazon.com>
---
 xen/arch/arm/arm32/head.S | 56 ++++++++++++++++++++++-----------------
 1 file changed, 32 insertions(+), 24 deletions(-)

diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
index 46d93bebbabe..50f6fa4eb38d 100644
--- a/xen/arch/arm/arm32/head.S
+++ b/xen/arch/arm/arm32/head.S
@@ -358,13 +358,31 @@ cpu_init_done:
         mov   pc, r5                        /* Return address is in r5 */
 ENDPROC(cpu_init)
 
+/*
+ * Macro to find the slot number at a given page-table level
+ *
+ * slot:     slot computed
+ * virt:     virtual address
+ * lvl:      page-table level
+ *
+ * Note that ubxf is unpredictable when the end bit is above 32-bit. So we
+ * can't use it for first level offset.
+ */
+.macro get_table_slot, slot, virt, lvl
+    .if \lvl == 1
+        lsr   \slot, \virt, #XEN_PT_LEVEL_SHIFT(\lvl)
+    .else
+        ubfx  \slot, \virt, #XEN_PT_LEVEL_SHIFT(\lvl), #XEN_PT_LPAE_SHIFT
+    .endif
+.endm
+
 /*
  * 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
+ * lvl:     page-table level
  * mmu:     Is the MMU turned on/off. If not specified it will be off
  *
  * Preserves \virt
@@ -374,11 +392,9 @@ ENDPROC(cpu_init)
  *
  * Note that \virt should be in a register other than r1 - r4
  */
-.macro create_table_entry, ptbl, tbl, virt, shift, mmu=0
-        lsr   r1, \virt, #\shift
-        mov_w r2, XEN_PT_LPAE_ENTRY_MASK
-        and   r1, r1, r2             /* r1 := slot in \tlb */
-        lsl   r1, r1, #3             /* r1 := slot offset in \tlb */
+.macro create_table_entry, ptbl, tbl, virt, lvl, mmu=0
+        get_table_slot r1, \virt, \lvl  /* r1 := slot in \tlb */
+        lsl   r1, r1, #3                /* r1 := slot offset in \tlb */
 
         load_paddr r4, \tbl
 
@@ -448,8 +464,8 @@ ENDPROC(cpu_init)
 create_page_tables:
         /* Prepare the page-tables for mapping Xen */
         ldr   r0, =XEN_VIRT_START
-        create_table_entry boot_pgtable, boot_second, r0, FIRST_SHIFT
-        create_table_entry boot_second, boot_third, r0, SECOND_SHIFT
+        create_table_entry boot_pgtable, boot_second, r0, 1
+        create_table_entry boot_second, boot_third, r0, 2
 
         /* Setup boot_third: */
         adr_l r4, boot_third, mmu=0
@@ -486,12 +502,10 @@ create_page_tables:
          * then the 1:1 mapping will use its own set of page-tables from
          * the second level.
          */
-        lsr   r1, r9, #FIRST_SHIFT
-        mov_w r0, XEN_PT_LPAE_ENTRY_MASK
-        and   r1, r1, r0              /* r1 := first slot */
+        get_table_slot r1, r9, 1     /* r1 := first slot */
         cmp   r1, #XEN_FIRST_SLOT
         beq   1f
-        create_table_entry boot_pgtable, boot_second_id, r9, FIRST_SHIFT
+        create_table_entry boot_pgtable, boot_second_id, r9, 1
         b     link_from_second_id
 
 1:
@@ -501,16 +515,14 @@ create_page_tables:
          * third level. For slot XEN_SECOND_SLOT, Xen is not yet able to handle
          * it.
          */
-        lsr   r1, r9, #SECOND_SHIFT
-        mov_w r0, XEN_PT_LPAE_ENTRY_MASK
-        and   r1, r1, r0             /* r1 := second slot */
+        get_table_slot r1, r9, 2     /* r1 := second slot */
         cmp   r1, #XEN_SECOND_SLOT
         beq   virtphys_clash
-        create_table_entry boot_second, boot_third_id, r9, SECOND_SHIFT
+        create_table_entry boot_second, boot_third_id, r9, 2
         b     link_from_third_id
 
 link_from_second_id:
-        create_table_entry boot_second_id, boot_third_id, r9, SECOND_SHIFT
+        create_table_entry boot_second_id, boot_third_id, r9, 2
 link_from_third_id:
         create_mapping_entry boot_third_id, r9, r9
         mov   pc, lr
@@ -571,9 +583,7 @@ remove_identity_mapping:
          * Find the first slot used. Remove the entry for the first
          * table if the slot is not XEN_FIRST_SLOT.
          */
-        lsr   r1, r9, #FIRST_SHIFT
-        mov_w r0, XEN_PT_LPAE_ENTRY_MASK
-        and   r1, r1, r0              /* r1 := first slot */
+        get_table_slot r1, r9, 1     /* r1 := first slot */
         cmp   r1, #XEN_FIRST_SLOT
         beq   1f
         /* It is not in slot 0, remove the entry */
@@ -587,9 +597,7 @@ remove_identity_mapping:
          * Find the second slot used. Remove the entry for the first
          * table if the slot is not XEN_SECOND_SLOT.
          */
-        lsr   r1, r9, #SECOND_SHIFT
-        mov_w r0, XEN_PT_LPAE_ENTRY_MASK
-        and   r1, r1, r0             /* r1 := second slot */
+        get_table_slot r1, r9, 2     /* r1 := second slot */
         cmp   r1, #XEN_SECOND_SLOT
         beq   identity_mapping_removed
         /* It is not in slot 1, remove the entry */
@@ -628,7 +636,7 @@ setup_fixmap:
 #endif
         /* Map fixmap into boot_second */
         mov_w r0, FIXMAP_ADDR(0)
-        create_table_entry boot_second, xen_fixmap, r0, SECOND_SHIFT, mmu=1
+        create_table_entry boot_second, xen_fixmap, r0, 2, mmu=1
         /* Ensure any page table updates made above have occurred. */
         dsb   nshst
 
-- 
2.37.1

Re: [PATCH 3/7] xen/arm32: head: Introduce get_table_slot() and use it

[Wei Chen]

Hi Julien,

On 2022/8/13 3:24, Julien Grall wrote:
> From: Julien Grall <jgrall@amazon.com>
> 
> There are a few places in the code that need to find the slot at a
> given page-table level.
> 
> So create a new macro get_table_slot() for that. This will reduce
> the effort to figure out whether the code is doing the right thing.
> 
> The new macro is using 'ubfx' (or 'lsr' for the first level) rather
> than the existing sequence (mov_w, lsr, and) because it doesn't require
> a scratch register and reduce the number of instructions (4 -> 1).
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
> ---
>   xen/arch/arm/arm32/head.S | 56 ++++++++++++++++++++++-----------------
>   1 file changed, 32 insertions(+), 24 deletions(-)
> 
> diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> index 46d93bebbabe..50f6fa4eb38d 100644
> --- a/xen/arch/arm/arm32/head.S
> +++ b/xen/arch/arm/arm32/head.S
> @@ -358,13 +358,31 @@ cpu_init_done:
>           mov   pc, r5                        /* Return address is in r5 */
>   ENDPROC(cpu_init)
>   
> +/*
> + * Macro to find the slot number at a given page-table level
> + *
> + * slot:     slot computed
> + * virt:     virtual address
> + * lvl:      page-table level
> + *
> + * Note that ubxf is unpredictable when the end bit is above 32-bit. So we
> + * can't use it for first level offset.
> + */
> +.macro get_table_slot, slot, virt, lvl
> +    .if \lvl == 1
> +        lsr   \slot, \virt, #XEN_PT_LEVEL_SHIFT(\lvl)
> +    .else
> +        ubfx  \slot, \virt, #XEN_PT_LEVEL_SHIFT(\lvl), #XEN_PT_LPAE_SHIFT
> +    .endif
> +.endm
> +
>   /*
>    * 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
> + * lvl:     page-table level
>    * mmu:     Is the MMU turned on/off. If not specified it will be off
>    *
>    * Preserves \virt
> @@ -374,11 +392,9 @@ ENDPROC(cpu_init)
>    *
>    * Note that \virt should be in a register other than r1 - r4
>    */
> -.macro create_table_entry, ptbl, tbl, virt, shift, mmu=0
> -        lsr   r1, \virt, #\shift
> -        mov_w r2, XEN_PT_LPAE_ENTRY_MASK
> -        and   r1, r1, r2             /* r1 := slot in \tlb */
> -        lsl   r1, r1, #3             /* r1 := slot offset in \tlb */
> +.macro create_table_entry, ptbl, tbl, virt, lvl, mmu=0
> +        get_table_slot r1, \virt, \lvl  /* r1 := slot in \tlb */
> +        lsl   r1, r1, #3                /* r1 := slot offset in \tlb */
>   
>           load_paddr r4, \tbl
>   
> @@ -448,8 +464,8 @@ ENDPROC(cpu_init)
>   create_page_tables:
>           /* Prepare the page-tables for mapping Xen */
>           ldr   r0, =XEN_VIRT_START
> -        create_table_entry boot_pgtable, boot_second, r0, FIRST_SHIFT
> -        create_table_entry boot_second, boot_third, r0, SECOND_SHIFT
> +        create_table_entry boot_pgtable, boot_second, r0, 1
> +        create_table_entry boot_second, boot_third, r0, 2
>   
>           /* Setup boot_third: */
>           adr_l r4, boot_third, mmu=0
> @@ -486,12 +502,10 @@ create_page_tables:
>            * then the 1:1 mapping will use its own set of page-tables from
>            * the second level.
>            */
> -        lsr   r1, r9, #FIRST_SHIFT
> -        mov_w r0, XEN_PT_LPAE_ENTRY_MASK
> -        and   r1, r1, r0              /* r1 := first slot */
> +        get_table_slot r1, r9, 1     /* r1 := first slot */
>           cmp   r1, #XEN_FIRST_SLOT
>           beq   1f
> -        create_table_entry boot_pgtable, boot_second_id, r9, FIRST_SHIFT
> +        create_table_entry boot_pgtable, boot_second_id, r9, 1
>           b     link_from_second_id
>   
>   1:
> @@ -501,16 +515,14 @@ create_page_tables:
>            * third level. For slot XEN_SECOND_SLOT, Xen is not yet able to handle
>            * it.
>            */
> -        lsr   r1, r9, #SECOND_SHIFT
> -        mov_w r0, XEN_PT_LPAE_ENTRY_MASK
> -        and   r1, r1, r0             /* r1 := second slot */
> +        get_table_slot r1, r9, 2     /* r1 := second slot */
>           cmp   r1, #XEN_SECOND_SLOT
>           beq   virtphys_clash
> -        create_table_entry boot_second, boot_third_id, r9, SECOND_SHIFT
> +        create_table_entry boot_second, boot_third_id, r9, 2
>           b     link_from_third_id
>   
>   link_from_second_id:
> -        create_table_entry boot_second_id, boot_third_id, r9, SECOND_SHIFT
> +        create_table_entry boot_second_id, boot_third_id, r9, 2
>   link_from_third_id:
>           create_mapping_entry boot_third_id, r9, r9
>           mov   pc, lr
> @@ -571,9 +583,7 @@ remove_identity_mapping:
>            * Find the first slot used. Remove the entry for the first
>            * table if the slot is not XEN_FIRST_SLOT.
>            */
> -        lsr   r1, r9, #FIRST_SHIFT
> -        mov_w r0, XEN_PT_LPAE_ENTRY_MASK
> -        and   r1, r1, r0              /* r1 := first slot */
> +        get_table_slot r1, r9, 1     /* r1 := first slot */
>           cmp   r1, #XEN_FIRST_SLOT
>           beq   1f
>           /* It is not in slot 0, remove the entry */
> @@ -587,9 +597,7 @@ remove_identity_mapping:
>            * Find the second slot used. Remove the entry for the first
>            * table if the slot is not XEN_SECOND_SLOT.
>            */
> -        lsr   r1, r9, #SECOND_SHIFT
> -        mov_w r0, XEN_PT_LPAE_ENTRY_MASK
> -        and   r1, r1, r0             /* r1 := second slot */
> +        get_table_slot r1, r9, 2     /* r1 := second slot */
>           cmp   r1, #XEN_SECOND_SLOT
>           beq   identity_mapping_removed
>           /* It is not in slot 1, remove the entry */
> @@ -628,7 +636,7 @@ setup_fixmap:
>   #endif
>           /* Map fixmap into boot_second */
>           mov_w r0, FIXMAP_ADDR(0)
> -        create_table_entry boot_second, xen_fixmap, r0, SECOND_SHIFT, mmu=1
> +        create_table_entry boot_second, xen_fixmap, r0, 2, mmu=1
>           /* Ensure any page table updates made above have occurred. */
>           dsb   nshst
>   

Reviewed-by: Wei Chen <Wei.Chen@arm.com>

Re: [PATCH 3/7] xen/arm32: head: Introduce get_table_slot() and use it

[Bertrand Marquis]

Hi Julien,

> On 12 Aug 2022, at 20:24, Julien Grall <julien@xen.org> wrote:
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> There are a few places in the code that need to find the slot at a
> given page-table level.
> 
> So create a new macro get_table_slot() for that. This will reduce
> the effort to figure out whether the code is doing the right thing.
> 
> The new macro is using 'ubfx' (or 'lsr' for the first level) rather
> than the existing sequence (mov_w, lsr, and) because it doesn't require
> a scratch register and reduce the number of instructions (4 -> 1).
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

Also I passed our test suite on arm32 qemu so:
Tested-by: Bertrand Marquis <bertrand.marquis@arm.com>

Cheers
Bertrand


> ---
> xen/arch/arm/arm32/head.S | 56 ++++++++++++++++++++++-----------------
> 1 file changed, 32 insertions(+), 24 deletions(-)
> 
> diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> index 46d93bebbabe..50f6fa4eb38d 100644
> --- a/xen/arch/arm/arm32/head.S
> +++ b/xen/arch/arm/arm32/head.S
> @@ -358,13 +358,31 @@ cpu_init_done:
>         mov   pc, r5                        /* Return address is in r5 */
> ENDPROC(cpu_init)
> 
> +/*
> + * Macro to find the slot number at a given page-table level
> + *
> + * slot:     slot computed
> + * virt:     virtual address
> + * lvl:      page-table level
> + *
> + * Note that ubxf is unpredictable when the end bit is above 32-bit. So we
> + * can't use it for first level offset.
> + */
> +.macro get_table_slot, slot, virt, lvl
> +    .if \lvl == 1
> +        lsr   \slot, \virt, #XEN_PT_LEVEL_SHIFT(\lvl)
> +    .else
> +        ubfx  \slot, \virt, #XEN_PT_LEVEL_SHIFT(\lvl), #XEN_PT_LPAE_SHIFT
> +    .endif
> +.endm
> +
> /*
>  * 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
> + * lvl:     page-table level
>  * mmu:     Is the MMU turned on/off. If not specified it will be off
>  *
>  * Preserves \virt
> @@ -374,11 +392,9 @@ ENDPROC(cpu_init)
>  *
>  * Note that \virt should be in a register other than r1 - r4
>  */
> -.macro create_table_entry, ptbl, tbl, virt, shift, mmu=0
> -        lsr   r1, \virt, #\shift
> -        mov_w r2, XEN_PT_LPAE_ENTRY_MASK
> -        and   r1, r1, r2             /* r1 := slot in \tlb */
> -        lsl   r1, r1, #3             /* r1 := slot offset in \tlb */
> +.macro create_table_entry, ptbl, tbl, virt, lvl, mmu=0
> +        get_table_slot r1, \virt, \lvl  /* r1 := slot in \tlb */
> +        lsl   r1, r1, #3                /* r1 := slot offset in \tlb */
> 
>         load_paddr r4, \tbl
> 
> @@ -448,8 +464,8 @@ ENDPROC(cpu_init)
> create_page_tables:
>         /* Prepare the page-tables for mapping Xen */
>         ldr   r0, =XEN_VIRT_START
> -        create_table_entry boot_pgtable, boot_second, r0, FIRST_SHIFT
> -        create_table_entry boot_second, boot_third, r0, SECOND_SHIFT
> +        create_table_entry boot_pgtable, boot_second, r0, 1
> +        create_table_entry boot_second, boot_third, r0, 2
> 
>         /* Setup boot_third: */
>         adr_l r4, boot_third, mmu=0
> @@ -486,12 +502,10 @@ create_page_tables:
>          * then the 1:1 mapping will use its own set of page-tables from
>          * the second level.
>          */
> -        lsr   r1, r9, #FIRST_SHIFT
> -        mov_w r0, XEN_PT_LPAE_ENTRY_MASK
> -        and   r1, r1, r0              /* r1 := first slot */
> +        get_table_slot r1, r9, 1     /* r1 := first slot */
>         cmp   r1, #XEN_FIRST_SLOT
>         beq   1f
> -        create_table_entry boot_pgtable, boot_second_id, r9, FIRST_SHIFT
> +        create_table_entry boot_pgtable, boot_second_id, r9, 1
>         b     link_from_second_id
> 
> 1:
> @@ -501,16 +515,14 @@ create_page_tables:
>          * third level. For slot XEN_SECOND_SLOT, Xen is not yet able to handle
>          * it.
>          */
> -        lsr   r1, r9, #SECOND_SHIFT
> -        mov_w r0, XEN_PT_LPAE_ENTRY_MASK
> -        and   r1, r1, r0             /* r1 := second slot */
> +        get_table_slot r1, r9, 2     /* r1 := second slot */
>         cmp   r1, #XEN_SECOND_SLOT
>         beq   virtphys_clash
> -        create_table_entry boot_second, boot_third_id, r9, SECOND_SHIFT
> +        create_table_entry boot_second, boot_third_id, r9, 2
>         b     link_from_third_id
> 
> link_from_second_id:
> -        create_table_entry boot_second_id, boot_third_id, r9, SECOND_SHIFT
> +        create_table_entry boot_second_id, boot_third_id, r9, 2
> link_from_third_id:
>         create_mapping_entry boot_third_id, r9, r9
>         mov   pc, lr
> @@ -571,9 +583,7 @@ remove_identity_mapping:
>          * Find the first slot used. Remove the entry for the first
>          * table if the slot is not XEN_FIRST_SLOT.
>          */
> -        lsr   r1, r9, #FIRST_SHIFT
> -        mov_w r0, XEN_PT_LPAE_ENTRY_MASK
> -        and   r1, r1, r0              /* r1 := first slot */
> +        get_table_slot r1, r9, 1     /* r1 := first slot */
>         cmp   r1, #XEN_FIRST_SLOT
>         beq   1f
>         /* It is not in slot 0, remove the entry */
> @@ -587,9 +597,7 @@ remove_identity_mapping:
>          * Find the second slot used. Remove the entry for the first
>          * table if the slot is not XEN_SECOND_SLOT.
>          */
> -        lsr   r1, r9, #SECOND_SHIFT
> -        mov_w r0, XEN_PT_LPAE_ENTRY_MASK
> -        and   r1, r1, r0             /* r1 := second slot */
> +        get_table_slot r1, r9, 2     /* r1 := second slot */
>         cmp   r1, #XEN_SECOND_SLOT
>         beq   identity_mapping_removed
>         /* It is not in slot 1, remove the entry */
> @@ -628,7 +636,7 @@ setup_fixmap:
> #endif
>         /* Map fixmap into boot_second */
>         mov_w r0, FIXMAP_ADDR(0)
> -        create_table_entry boot_second, xen_fixmap, r0, SECOND_SHIFT, mmu=1
> +        create_table_entry boot_second, xen_fixmap, r0, 2, mmu=1
>         /* Ensure any page table updates made above have occurred. */
>         dsb   nshst
> 
> -- 
> 2.37.1
> 

[PATCH 4/7] xen/arm32: heap: Rework adr_l so it doesn't rely on where Xen is loaded

[Julien Grall]

From: Julien Grall <jgrall@amazon.com>

At the moment, the macro addr_l needs to know whether the caller
is running with the MMU on. This is fine today because there are
only two possible cases:
 1) MMU off
 2) MMU on and linked to the virtual address

This is still cumbersome to use for the developer as they need
to know if the MMU is on.

Thankfully, Linux developpers came up with a great way to allow
adr_l to work within the range +/- 4GB of PC by emitting a PC-relative
reference [1].

Re-use the same approach on Arm and drop the parameter 'mmu'.

[1] 0b1674638a5c ("ARM: assembler: introduce adr_l, ldr_l and str_l macros")

Signed-off-by: Julien Grall <jgrall@amazon.com>

----
    I haven't added an Origin tag because this is quite different
    from the Linux commit. I am happy to add one if this is desired..
---
 xen/arch/arm/arm32/head.S | 38 +++++++++++++++-----------------------
 1 file changed, 15 insertions(+), 23 deletions(-)

diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
index 50f6fa4eb38d..27d02ac8d68f 100644
--- a/xen/arch/arm/arm32/head.S
+++ b/xen/arch/arm/arm32/head.S
@@ -49,20 +49,16 @@
 .endm
 
 /*
- * There are no easy way to have a PC relative address within the range
- * +/- 4GB of the PC.
+ * Pseudo-op for PC relative adr <reg>, <symbol> where <symbol> is
+ * within the range +/- 4GB of the PC.
  *
- * This macro workaround it by asking the user to tell whether the MMU
- * has been turned on or not.
- *
- * When the MMU is turned off, we need to apply the physical offset
- * (r10) in order to find the associated physical address.
+ * @dst: destination register
+ * @sym: name of the symbol
  */
-.macro adr_l, dst, sym, mmu
-        ldr   \dst, =\sym
-        .if \mmu == 0
-        add   \dst, \dst, r10
-        .endif
+.macro adr_l, dst, sym
+        mov_w \dst, \sym - .Lpc\@
+        .set  .Lpc\@, .+ 8          /* PC bias */
+        add   \dst, \dst, pc
 .endm
 
 .macro load_paddr rb, sym
@@ -383,7 +379,6 @@ ENDPROC(cpu_init)
  * tbl:     table symbol to point to
  * virt:    virtual address
  * lvl:     page-table level
- * mmu:     Is the MMU turned on/off. If not specified it will be off
  *
  * Preserves \virt
  * Clobbers r1 - r4
@@ -392,7 +387,7 @@ ENDPROC(cpu_init)
  *
  * Note that \virt should be in a register other than r1 - r4
  */
-.macro create_table_entry, ptbl, tbl, virt, lvl, mmu=0
+.macro create_table_entry, ptbl, tbl, virt, lvl
         get_table_slot r1, \virt, \lvl  /* r1 := slot in \tlb */
         lsl   r1, r1, #3                /* r1 := slot offset in \tlb */
 
@@ -402,7 +397,7 @@ ENDPROC(cpu_init)
         orr   r2, r2, r4             /*           + \tlb paddr */
         mov   r3, #0
 
-        adr_l r4, \ptbl, \mmu
+        adr_l r4, \ptbl
 
         strd  r2, r3, [r4, r1]
 .endm
@@ -415,17 +410,14 @@ ENDPROC(cpu_init)
  * virt:    virtual address
  * phys:    physical address
  * type:    mapping type. If not specified it will be normal memory (PT_MEM_L3)
- * mmu:     Is the MMU turned on/off. If not specified it will be off
  *
  * Preserves \virt, \phys
  * Clobbers r1 - r4
  *
- * * Also use r10 for the phys offset.
- *
  * Note that \virt and \paddr should be in other registers than r1 - r4
  * and be distinct.
  */
-.macro create_mapping_entry, ptbl, virt, phys, type=PT_MEM_L3, mmu=0
+.macro create_mapping_entry, ptbl, virt, phys, type=PT_MEM_L3
         mov_w r2, XEN_PT_LPAE_ENTRY_MASK
         lsr   r1, \virt, #THIRD_SHIFT
         and   r1, r1, r2             /* r1 := slot in \tlb */
@@ -438,7 +430,7 @@ ENDPROC(cpu_init)
         orr   r2, r2, r4             /*          + PAGE_ALIGNED(phys) */
         mov   r3, #0
 
-        adr_l r4, \ptbl, \mmu
+        adr_l r4, \ptbl
 
         strd  r2, r3, [r4, r1]
 .endm
@@ -468,7 +460,7 @@ create_page_tables:
         create_table_entry boot_second, boot_third, r0, 2
 
         /* Setup boot_third: */
-        adr_l r4, boot_third, mmu=0
+        adr_l r4, boot_third
 
         lsr   r2, r9, #THIRD_SHIFT  /* Base address for 4K mapping */
         lsl   r2, r2, #THIRD_SHIFT
@@ -632,11 +624,11 @@ setup_fixmap:
 #if defined(CONFIG_EARLY_PRINTK)
         /* Add UART to the fixmap table */
         ldr   r0, =EARLY_UART_VIRTUAL_ADDRESS
-        create_mapping_entry xen_fixmap, r0, r11, type=PT_DEV_L3, mmu=1
+        create_mapping_entry xen_fixmap, r0, r11, type=PT_DEV_L3
 #endif
         /* Map fixmap into boot_second */
         mov_w r0, FIXMAP_ADDR(0)
-        create_table_entry boot_second, xen_fixmap, r0, 2, mmu=1
+        create_table_entry boot_second, xen_fixmap, r0, 2
         /* Ensure any page table updates made above have occurred. */
         dsb   nshst
 
-- 
2.37.1

Re: [PATCH 4/7] xen/arm32: heap: Rework adr_l so it doesn't rely on where Xen is loaded

[Wei Chen]

Hi Julien,

On 2022/8/13 3:24, Julien Grall wrote:
> From: Julien Grall <jgrall@amazon.com>
> 
> At the moment, the macro addr_l needs to know whether the caller
> is running with the MMU on. This is fine today because there are
> only two possible cases:
>   1) MMU off
>   2) MMU on and linked to the virtual address
> 
> This is still cumbersome to use for the developer as they need
> to know if the MMU is on.
> 
> Thankfully, Linux developpers came up with a great way to allow
> adr_l to work within the range +/- 4GB of PC by emitting a PC-relative
> reference [1].
> 
> Re-use the same approach on Arm and drop the parameter 'mmu'.
> 
> [1] 0b1674638a5c ("ARM: assembler: introduce adr_l, ldr_l and str_l macros")
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
> 
> ----
>      I haven't added an Origin tag because this is quite different
>      from the Linux commit. I am happy to add one if this is desired..
> ---
>   xen/arch/arm/arm32/head.S | 38 +++++++++++++++-----------------------
>   1 file changed, 15 insertions(+), 23 deletions(-)
> 
> diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> index 50f6fa4eb38d..27d02ac8d68f 100644
> --- a/xen/arch/arm/arm32/head.S
> +++ b/xen/arch/arm/arm32/head.S
> @@ -49,20 +49,16 @@
>   .endm
>   
>   /*
> - * There are no easy way to have a PC relative address within the range
> - * +/- 4GB of the PC.
> + * Pseudo-op for PC relative adr <reg>, <symbol> where <symbol> is
> + * within the range +/- 4GB of the PC.
>    *
> - * This macro workaround it by asking the user to tell whether the MMU
> - * has been turned on or not.
> - *
> - * When the MMU is turned off, we need to apply the physical offset
> - * (r10) in order to find the associated physical address.
> + * @dst: destination register
> + * @sym: name of the symbol
>    */
> -.macro adr_l, dst, sym, mmu
> -        ldr   \dst, =\sym
> -        .if \mmu == 0
> -        add   \dst, \dst, r10
> -        .endif
> +.macro adr_l, dst, sym
> +        mov_w \dst, \sym - .Lpc\@
> +        .set  .Lpc\@, .+ 8          /* PC bias */
> +        add   \dst, \dst, pc
>   .endm
>   
>   .macro load_paddr rb, sym
> @@ -383,7 +379,6 @@ ENDPROC(cpu_init)
>    * tbl:     table symbol to point to
>    * virt:    virtual address
>    * lvl:     page-table level
> - * mmu:     Is the MMU turned on/off. If not specified it will be off
>    *
>    * Preserves \virt
>    * Clobbers r1 - r4
> @@ -392,7 +387,7 @@ ENDPROC(cpu_init)
>    *
>    * Note that \virt should be in a register other than r1 - r4
>    */
> -.macro create_table_entry, ptbl, tbl, virt, lvl, mmu=0
> +.macro create_table_entry, ptbl, tbl, virt, lvl
>           get_table_slot r1, \virt, \lvl  /* r1 := slot in \tlb */
>           lsl   r1, r1, #3                /* r1 := slot offset in \tlb */
>   
> @@ -402,7 +397,7 @@ ENDPROC(cpu_init)
>           orr   r2, r2, r4             /*           + \tlb paddr */
>           mov   r3, #0
>   
> -        adr_l r4, \ptbl, \mmu
> +        adr_l r4, \ptbl
>   
>           strd  r2, r3, [r4, r1]
>   .endm
> @@ -415,17 +410,14 @@ ENDPROC(cpu_init)
>    * virt:    virtual address
>    * phys:    physical address
>    * type:    mapping type. If not specified it will be normal memory (PT_MEM_L3)
> - * mmu:     Is the MMU turned on/off. If not specified it will be off
>    *
>    * Preserves \virt, \phys
>    * Clobbers r1 - r4
>    *
> - * * Also use r10 for the phys offset.
> - *
>    * Note that \virt and \paddr should be in other registers than r1 - r4
>    * and be distinct.
>    */
> -.macro create_mapping_entry, ptbl, virt, phys, type=PT_MEM_L3, mmu=0
> +.macro create_mapping_entry, ptbl, virt, phys, type=PT_MEM_L3
>           mov_w r2, XEN_PT_LPAE_ENTRY_MASK
>           lsr   r1, \virt, #THIRD_SHIFT
>           and   r1, r1, r2             /* r1 := slot in \tlb */
> @@ -438,7 +430,7 @@ ENDPROC(cpu_init)
>           orr   r2, r2, r4             /*          + PAGE_ALIGNED(phys) */
>           mov   r3, #0
>   
> -        adr_l r4, \ptbl, \mmu
> +        adr_l r4, \ptbl
>   
>           strd  r2, r3, [r4, r1]
>   .endm
> @@ -468,7 +460,7 @@ create_page_tables:
>           create_table_entry boot_second, boot_third, r0, 2
>   
>           /* Setup boot_third: */
> -        adr_l r4, boot_third, mmu=0
> +        adr_l r4, boot_third
>   
>           lsr   r2, r9, #THIRD_SHIFT  /* Base address for 4K mapping */
>           lsl   r2, r2, #THIRD_SHIFT
> @@ -632,11 +624,11 @@ setup_fixmap:
>   #if defined(CONFIG_EARLY_PRINTK)
>           /* Add UART to the fixmap table */
>           ldr   r0, =EARLY_UART_VIRTUAL_ADDRESS
> -        create_mapping_entry xen_fixmap, r0, r11, type=PT_DEV_L3, mmu=1
> +        create_mapping_entry xen_fixmap, r0, r11, type=PT_DEV_L3
>   #endif
>           /* Map fixmap into boot_second */
>           mov_w r0, FIXMAP_ADDR(0)
> -        create_table_entry boot_second, xen_fixmap, r0, 2, mmu=1
> +        create_table_entry boot_second, xen_fixmap, r0, 2
>           /* Ensure any page table updates made above have occurred. */
>           dsb   nshst
>   

LGTM.

Reviewed-by: Wei Chen <Wei.Chen@arm.com>

Re: [PATCH 4/7] xen/arm32: heap: Rework adr_l so it doesn't rely on where Xen is loaded

[Bertrand Marquis]

Hi Julien,

> On 12 Aug 2022, at 20:24, Julien Grall <julien@xen.org> wrote:
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> At the moment, the macro addr_l needs to know whether the caller
> is running with the MMU on. This is fine today because there are
> only two possible cases:
> 1) MMU off
> 2) MMU on and linked to the virtual address
> 
> This is still cumbersome to use for the developer as they need
> to know if the MMU is on.
> 
> Thankfully, Linux developpers came up with a great way to allow
> adr_l to work within the range +/- 4GB of PC by emitting a PC-relative
> reference [1].

This is indeed a great solution :-)

> 
> Re-use the same approach on Arm and drop the parameter 'mmu'.
> 
> [1] 0b1674638a5c ("ARM: assembler: introduce adr_l, ldr_l and str_l macros")
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

> 
> ----
>    I haven't added an Origin tag because this is quite different
>    from the Linux commit. I am happy to add one if this is desired..

I think the reference in the commit message is enough as you reuse the
idea but not the code per say.

Cheers
Bertrand

> ---
> xen/arch/arm/arm32/head.S | 38 +++++++++++++++-----------------------
> 1 file changed, 15 insertions(+), 23 deletions(-)
> 
> diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> index 50f6fa4eb38d..27d02ac8d68f 100644
> --- a/xen/arch/arm/arm32/head.S
> +++ b/xen/arch/arm/arm32/head.S
> @@ -49,20 +49,16 @@
> .endm
> 
> /*
> - * There are no easy way to have a PC relative address within the range
> - * +/- 4GB of the PC.
> + * Pseudo-op for PC relative adr <reg>, <symbol> where <symbol> is
> + * within the range +/- 4GB of the PC.
>  *
> - * This macro workaround it by asking the user to tell whether the MMU
> - * has been turned on or not.
> - *
> - * When the MMU is turned off, we need to apply the physical offset
> - * (r10) in order to find the associated physical address.
> + * @dst: destination register
> + * @sym: name of the symbol
>  */
> -.macro adr_l, dst, sym, mmu
> -        ldr   \dst, =\sym
> -        .if \mmu == 0
> -        add   \dst, \dst, r10
> -        .endif
> +.macro adr_l, dst, sym
> +        mov_w \dst, \sym - .Lpc\@
> +        .set  .Lpc\@, .+ 8          /* PC bias */
> +        add   \dst, \dst, pc
> .endm
> 
> .macro load_paddr rb, sym
> @@ -383,7 +379,6 @@ ENDPROC(cpu_init)
>  * tbl:     table symbol to point to
>  * virt:    virtual address
>  * lvl:     page-table level
> - * mmu:     Is the MMU turned on/off. If not specified it will be off
>  *
>  * Preserves \virt
>  * Clobbers r1 - r4
> @@ -392,7 +387,7 @@ ENDPROC(cpu_init)
>  *
>  * Note that \virt should be in a register other than r1 - r4
>  */
> -.macro create_table_entry, ptbl, tbl, virt, lvl, mmu=0
> +.macro create_table_entry, ptbl, tbl, virt, lvl
>         get_table_slot r1, \virt, \lvl  /* r1 := slot in \tlb */
>         lsl   r1, r1, #3                /* r1 := slot offset in \tlb */
> 
> @@ -402,7 +397,7 @@ ENDPROC(cpu_init)
>         orr   r2, r2, r4             /*           + \tlb paddr */
>         mov   r3, #0
> 
> -        adr_l r4, \ptbl, \mmu
> +        adr_l r4, \ptbl
> 
>         strd  r2, r3, [r4, r1]
> .endm
> @@ -415,17 +410,14 @@ ENDPROC(cpu_init)
>  * virt:    virtual address
>  * phys:    physical address
>  * type:    mapping type. If not specified it will be normal memory (PT_MEM_L3)
> - * mmu:     Is the MMU turned on/off. If not specified it will be off
>  *
>  * Preserves \virt, \phys
>  * Clobbers r1 - r4
>  *
> - * * Also use r10 for the phys offset.
> - *
>  * Note that \virt and \paddr should be in other registers than r1 - r4
>  * and be distinct.
>  */
> -.macro create_mapping_entry, ptbl, virt, phys, type=PT_MEM_L3, mmu=0
> +.macro create_mapping_entry, ptbl, virt, phys, type=PT_MEM_L3
>         mov_w r2, XEN_PT_LPAE_ENTRY_MASK
>         lsr   r1, \virt, #THIRD_SHIFT
>         and   r1, r1, r2             /* r1 := slot in \tlb */
> @@ -438,7 +430,7 @@ ENDPROC(cpu_init)
>         orr   r2, r2, r4             /*          + PAGE_ALIGNED(phys) */
>         mov   r3, #0
> 
> -        adr_l r4, \ptbl, \mmu
> +        adr_l r4, \ptbl
> 
>         strd  r2, r3, [r4, r1]
> .endm
> @@ -468,7 +460,7 @@ create_page_tables:
>         create_table_entry boot_second, boot_third, r0, 2
> 
>         /* Setup boot_third: */
> -        adr_l r4, boot_third, mmu=0
> +        adr_l r4, boot_third
> 
>         lsr   r2, r9, #THIRD_SHIFT  /* Base address for 4K mapping */
>         lsl   r2, r2, #THIRD_SHIFT
> @@ -632,11 +624,11 @@ setup_fixmap:
> #if defined(CONFIG_EARLY_PRINTK)
>         /* Add UART to the fixmap table */
>         ldr   r0, =EARLY_UART_VIRTUAL_ADDRESS
> -        create_mapping_entry xen_fixmap, r0, r11, type=PT_DEV_L3, mmu=1
> +        create_mapping_entry xen_fixmap, r0, r11, type=PT_DEV_L3
> #endif
>         /* Map fixmap into boot_second */
>         mov_w r0, FIXMAP_ADDR(0)
> -        create_table_entry boot_second, xen_fixmap, r0, 2, mmu=1
> +        create_table_entry boot_second, xen_fixmap, r0, 2
>         /* Ensure any page table updates made above have occurred. */
>         dsb   nshst
> 
> -- 
> 2.37.1
> 

[PATCH 5/7] xen/arm32: head: Move earlyprintk messages to .rodata.str

[Julien Grall]

From: Julien Grall <jgrall@amazon.com>

At the moment, the strings are in text right after each use because
the instruction 'adr' has specific requirement on the location
and the compiler will forbid cross section label.

The macro 'adr_l' was recently reworked so the caller doesn't need
to know whether the MMU is on. This makes it easier to use where
instructions can be run in both context.

This also means that the strings don't need to be part of .text
anymore. So move them to .rodata.str.

Signed-off-by: Julien Grall <jgrall@amazon.com>
---
 xen/arch/arm/arm32/head.S | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
index 27d02ac8d68f..a558c2a6876e 100644
--- a/xen/arch/arm/arm32/head.S
+++ b/xen/arch/arm/arm32/head.S
@@ -93,13 +93,10 @@
  */
 #define PRINT(_s)           \
         mov   r3, lr       ;\
-        adr   r0, 98f      ;\
+        adr_l r0, 98f      ;\
         bl    puts         ;\
         mov   lr, r3       ;\
-        b     99f          ;\
-98:     .asciz _s          ;\
-        .align 2           ;\
-99:
+        RODATA_STR(98, _s)
 
 /*
  * Macro to print the value of register \rb
@@ -736,7 +733,7 @@ ENDPROC(puts)
  * Clobbers r0-r3
  */
 putn:
-        adr   r1, hex
+        adr_l r1, hex
         mov   r3, #8
 1:
         early_uart_ready r11, r2
@@ -749,8 +746,7 @@ putn:
         mov   pc, lr
 ENDPROC(putn)
 
-hex:    .ascii "0123456789abcdef"
-        .align 2
+RODATA_STR(hex, "0123456789abcdef")
 
 #else  /* CONFIG_EARLY_PRINTK */
 
-- 
2.37.1

RE: [PATCH 5/7] xen/arm32: head: Move earlyprintk messages to .rodata.str

[Jiamei Xie]

Hi Julien,

> -----Original Message-----
> From: Xen-devel <xen-devel-bounces@lists.xenproject.org> On Behalf Of
> Julien Grall
> Sent: Saturday, August 13, 2022 3:25 AM
> To: xen-devel@lists.xenproject.org
> Cc: julien@xen.org; Julien Grall <jgrall@amazon.com>; Stefano Stabellini
> <sstabellini@kernel.org>; Bertrand Marquis <Bertrand.Marquis@arm.com>;
> Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
> Subject: [PATCH 5/7] xen/arm32: head: Move earlyprintk messages
> to .rodata.str
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> At the moment, the strings are in text right after each use because
> the instruction 'adr' has specific requirement on the location
> and the compiler will forbid cross section label.
> 
> The macro 'adr_l' was recently reworked so the caller doesn't need
> to know whether the MMU is on. This makes it easier to use where
> instructions can be run in both context.
> 
> This also means that the strings don't need to be part of .text
> anymore. So move them to .rodata.str.
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
> ---
>  xen/arch/arm/arm32/head.S | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> index 27d02ac8d68f..a558c2a6876e 100644
> --- a/xen/arch/arm/arm32/head.S
> +++ b/xen/arch/arm/arm32/head.S
> @@ -93,13 +93,10 @@
>   */
>  #define PRINT(_s)           \
>          mov   r3, lr       ;\
> -        adr   r0, 98f      ;\
> +        adr_l r0, 98f      ;\
>          bl    puts         ;\
>          mov   lr, r3       ;\
> -        b     99f          ;\
> -98:     .asciz _s          ;\
> -        .align 2           ;\
> -99:
> +        RODATA_STR(98, _s)
> 
>  /*
>   * Macro to print the value of register \rb
> @@ -736,7 +733,7 @@ ENDPROC(puts)
>   * Clobbers r0-r3
>   */
>  putn:
> -        adr   r1, hex
> +        adr_l r1, hex
>          mov   r3, #8
>  1:
>          early_uart_ready r11, r2
> @@ -749,8 +746,7 @@ putn:
>          mov   pc, lr
>  ENDPROC(putn)
> 
> -hex:    .ascii "0123456789abcdef"
> -        .align 2
> +RODATA_STR(hex, "0123456789abcdef")
> 
>  #else  /* CONFIG_EARLY_PRINTK */
> 
> --
> 2.37.1
> 

That looks good to me.
Reviewed-by: Jiamei Xie <jiamei.xie@arm.com>

Best wishes
Jiamei Xie

Re: [PATCH 5/7] xen/arm32: head: Move earlyprintk messages to .rodata.str

[Wei Chen]

Hi Julien,


On 2022/8/13 3:24, Julien Grall wrote:
> From: Julien Grall <jgrall@amazon.com>
> 
> At the moment, the strings are in text right after each use because
> the instruction 'adr' has specific requirement on the location
> and the compiler will forbid cross section label.
> 
> The macro 'adr_l' was recently reworked so the caller doesn't need
> to know whether the MMU is on. This makes it easier to use where
> instructions can be run in both context.
> 
> This also means that the strings don't need to be part of .text
> anymore. So move them to .rodata.str.
> 

This sounds very good!

> Signed-off-by: Julien Grall <jgrall@amazon.com>
> ---
>   xen/arch/arm/arm32/head.S | 12 ++++--------
>   1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> index 27d02ac8d68f..a558c2a6876e 100644
> --- a/xen/arch/arm/arm32/head.S
> +++ b/xen/arch/arm/arm32/head.S
> @@ -93,13 +93,10 @@
>    */
>   #define PRINT(_s)           \
>           mov   r3, lr       ;\
> -        adr   r0, 98f      ;\
> +        adr_l r0, 98f      ;\
>           bl    puts         ;\
>           mov   lr, r3       ;\
> -        b     99f          ;\
> -98:     .asciz _s          ;\
> -        .align 2           ;\
> -99:
> +        RODATA_STR(98, _s)
>   
>   /*
>    * Macro to print the value of register \rb
> @@ -736,7 +733,7 @@ ENDPROC(puts)
>    * Clobbers r0-r3
>    */
>   putn:
> -        adr   r1, hex
> +        adr_l r1, hex
>           mov   r3, #8
>   1:
>           early_uart_ready r11, r2
> @@ -749,8 +746,7 @@ putn:
>           mov   pc, lr
>   ENDPROC(putn)
>   
> -hex:    .ascii "0123456789abcdef"
> -        .align 2
> +RODATA_STR(hex, "0123456789abcdef")
>   
>   #else  /* CONFIG_EARLY_PRINTK */
>   

Reviewed-by: Wei Chen <Wei.Chen@arm.com>

Re: [PATCH 5/7] xen/arm32: head: Move earlyprintk messages to .rodata.str

[Jan Beulich]

On 12.08.2022 21:24, Julien Grall wrote:
> From: Julien Grall <jgrall@amazon.com>
> 
> At the moment, the strings are in text right after each use because
> the instruction 'adr' has specific requirement on the location
> and the compiler will forbid cross section label.
> 
> The macro 'adr_l' was recently reworked so the caller doesn't need
> to know whether the MMU is on. This makes it easier to use where
> instructions can be run in both context.
> 
> This also means that the strings don't need to be part of .text
> anymore. So move them to .rodata.str.

Wouldn't they better live somewhere in .init* ?

> --- a/xen/arch/arm/arm32/head.S
> +++ b/xen/arch/arm/arm32/head.S
> @@ -93,13 +93,10 @@
>   */
>  #define PRINT(_s)           \
>          mov   r3, lr       ;\
> -        adr   r0, 98f      ;\
> +        adr_l r0, 98f      ;\
>          bl    puts         ;\
>          mov   lr, r3       ;\
> -        b     99f          ;\
> -98:     .asciz _s          ;\
> -        .align 2           ;\
> -99:
> +        RODATA_STR(98, _s)

Nit: How about using uniform indentation here  and ...

> @@ -736,7 +733,7 @@ ENDPROC(puts)
>   * Clobbers r0-r3
>   */
>  putn:
> -        adr   r1, hex
> +        adr_l r1, hex
>          mov   r3, #8
>  1:
>          early_uart_ready r11, r2
> @@ -749,8 +746,7 @@ putn:
>          mov   pc, lr
>  ENDPROC(putn)
>  
> -hex:    .ascii "0123456789abcdef"
> -        .align 2
> +RODATA_STR(hex, "0123456789abcdef")

... here?

Jan

Re: [PATCH 5/7] xen/arm32: head: Move earlyprintk messages to .rodata.str

[Julien Grall]

Hi Jan,

On 15/08/2022 07:43, Jan Beulich wrote:
> On 12.08.2022 21:24, Julien Grall wrote:
>> From: Julien Grall <jgrall@amazon.com>
>>
>> At the moment, the strings are in text right after each use because
>> the instruction 'adr' has specific requirement on the location
>> and the compiler will forbid cross section label.
>>
>> The macro 'adr_l' was recently reworked so the caller doesn't need
>> to know whether the MMU is on. This makes it easier to use where
>> instructions can be run in both context.
>>
>> This also means that the strings don't need to be part of .text
>> anymore. So move them to .rodata.str.
> 
> Wouldn't they better live somewhere in .init* ?

PRINT() is also used in path for secondary bring-up. So this could be 
used after .init (even though today CPU hotplug doesn't work on Arm).

Furthermore, PRINT() is only used when earlyprintk is enabled. This 
should only be used in a development environment (gated by 
CONFIG_DEBUG). So I think it is better to keep all the strings in 
.rodata.str rather than trying to distinguish whether the caller will 
happen only during init on boot.

Cheers,

-- 
Julien Grall

Re: [PATCH 5/7] xen/arm32: head: Move earlyprintk messages to .rodata.str

[Jan Beulich]

On 15.08.2022 10:17, Julien Grall wrote:
> On 15/08/2022 07:43, Jan Beulich wrote:
>> On 12.08.2022 21:24, Julien Grall wrote:
>>> From: Julien Grall <jgrall@amazon.com>
>>>
>>> At the moment, the strings are in text right after each use because
>>> the instruction 'adr' has specific requirement on the location
>>> and the compiler will forbid cross section label.
>>>
>>> The macro 'adr_l' was recently reworked so the caller doesn't need
>>> to know whether the MMU is on. This makes it easier to use where
>>> instructions can be run in both context.
>>>
>>> This also means that the strings don't need to be part of .text
>>> anymore. So move them to .rodata.str.
>>
>> Wouldn't they better live somewhere in .init* ?
> 
> PRINT() is also used in path for secondary bring-up. So this could be 
> used after .init (even though today CPU hotplug doesn't work on Arm).

Then the term "earlyprintk" looks to be misleading?

> Furthermore, PRINT() is only used when earlyprintk is enabled. This 
> should only be used in a development environment (gated by 
> CONFIG_DEBUG). So I think it is better to keep all the strings in 
> .rodata.str rather than trying to distinguish whether the caller will 
> happen only during init on boot.

Fair enough.

Jan

Re: [PATCH 5/7] xen/arm32: head: Move earlyprintk messages to .rodata.str

[Julien Grall]

Hi Jan,

On 15/08/2022 09:21, Jan Beulich wrote:
> On 15.08.2022 10:17, Julien Grall wrote:
>> On 15/08/2022 07:43, Jan Beulich wrote:
>>> On 12.08.2022 21:24, Julien Grall wrote:
>>>> From: Julien Grall <jgrall@amazon.com>
>>>>
>>>> At the moment, the strings are in text right after each use because
>>>> the instruction 'adr' has specific requirement on the location
>>>> and the compiler will forbid cross section label.
>>>>
>>>> The macro 'adr_l' was recently reworked so the caller doesn't need
>>>> to know whether the MMU is on. This makes it easier to use where
>>>> instructions can be run in both context.
>>>>
>>>> This also means that the strings don't need to be part of .text
>>>> anymore. So move them to .rodata.str.
>>>
>>> Wouldn't they better live somewhere in .init* ?
>>
>> PRINT() is also used in path for secondary bring-up. So this could be
>> used after .init (even though today CPU hotplug doesn't work on Arm).
> 
> Then the term "earlyprintk" looks to be misleading?
I can't think of a better name. "early" could also be interpreted as 
"early CPU bring-up".

Cheers,

-- 
Julien Grall

Re: [PATCH 5/7] xen/arm32: head: Move earlyprintk messages to .rodata.str

[Bertrand Marquis]

Hi Julien,

> On 12 Aug 2022, at 20:24, Julien Grall <julien@xen.org> wrote:
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> At the moment, the strings are in text right after each use because
> the instruction 'adr' has specific requirement on the location
> and the compiler will forbid cross section label.
> 
> The macro 'adr_l' was recently reworked so the caller doesn't need
> to know whether the MMU is on. This makes it easier to use where
> instructions can be run in both context.
> 
> This also means that the strings don't need to be part of .text
> anymore. So move them to .rodata.str.
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

Tested by enabling early printk on qemu arm32 and it works so:

Tested-by: Bertrand Marquis <bertrand.marquis@arm.com>

Cheers
Bertrand

> ---
> xen/arch/arm/arm32/head.S | 12 ++++--------
> 1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> index 27d02ac8d68f..a558c2a6876e 100644
> --- a/xen/arch/arm/arm32/head.S
> +++ b/xen/arch/arm/arm32/head.S
> @@ -93,13 +93,10 @@
>  */
> #define PRINT(_s)           \
>         mov   r3, lr       ;\
> -        adr   r0, 98f      ;\
> +        adr_l r0, 98f      ;\
>         bl    puts         ;\
>         mov   lr, r3       ;\
> -        b     99f          ;\
> -98:     .asciz _s          ;\
> -        .align 2           ;\
> -99:
> +        RODATA_STR(98, _s)
> 
> /*
>  * Macro to print the value of register \rb
> @@ -736,7 +733,7 @@ ENDPROC(puts)
>  * Clobbers r0-r3
>  */
> putn:
> -        adr   r1, hex
> +        adr_l r1, hex
>         mov   r3, #8
> 1:
>         early_uart_ready r11, r2
> @@ -749,8 +746,7 @@ putn:
>         mov   pc, lr
> ENDPROC(putn)
> 
> -hex:    .ascii "0123456789abcdef"
> -        .align 2
> +RODATA_STR(hex, "0123456789abcdef")
> 
> #else  /* CONFIG_EARLY_PRINTK */
> 
> -- 
> 2.37.1
> 

[PATCH 6/7] xen/arm: Tweak the dump page-table walk output

[Julien Grall]

From: Julien Grall <jgrall@amazon.com>

Currently the output is looking like:

(XEN) 1ST[0x1] = 0x000000004015ff7f
(XEN) 2ND[0x1f] = 0x00500000bfe00f7d

The content of the entries are not aligned making a bit trickier to
read (I appreciate this is a matter of taste).

Align the values by forcing the index to be always printed using
3 characters (enough to cover 512 in hexadecimal).

New output:

(XEN) 1ST[0x001] = 0x000000004015ff7f
(XEN) 2ND[0x01f] = 0x00500000bfe00f7d

Signed-off-by: Julien Grall <jgrall@amazon.com>
---
 xen/arch/arm/mm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index b42cddb1b446..c81c706c8b23 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -234,7 +234,7 @@ void dump_pt_walk(paddr_t ttbr, paddr_t addr,
 
         pte = mapping[offsets[level]];
 
-        printk("%s[0x%x] = 0x%"PRIpaddr"\n",
+        printk("%s[0x%03x] = 0x%"PRIpaddr"\n",
                level_strs[level], offsets[level], pte.bits);
 
         if ( level == 3 || !pte.walk.valid || !pte.walk.table )
-- 
2.37.1

RE: [PATCH 6/7] xen/arm: Tweak the dump page-table walk output

[Henry Wang]

Hi Julien,

> -----Original Message-----
> Subject: [PATCH 6/7] xen/arm: Tweak the dump page-table walk output
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> Currently the output is looking like:
> 
> (XEN) 1ST[0x1] = 0x000000004015ff7f
> (XEN) 2ND[0x1f] = 0x00500000bfe00f7d
> 
> The content of the entries are not aligned making a bit trickier to
> read (I appreciate this is a matter of taste).
> 
> Align the values by forcing the index to be always printed using
> 3 characters (enough to cover 512 in hexadecimal).
> 
> New output:
> 
> (XEN) 1ST[0x001] = 0x000000004015ff7f
> (XEN) 2ND[0x01f] = 0x00500000bfe00f7d
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>

Reviewed-by: Henry Wang <Henry.Wang@arm.com>

Kind regards,
Henry

Re: [PATCH 6/7] xen/arm: Tweak the dump page-table walk output

[Bertrand Marquis]

Hi Julien,

> On 12 Aug 2022, at 20:24, Julien Grall <julien@xen.org> wrote:
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> Currently the output is looking like:
> 
> (XEN) 1ST[0x1] = 0x000000004015ff7f
> (XEN) 2ND[0x1f] = 0x00500000bfe00f7d
> 
> The content of the entries are not aligned making a bit trickier to
> read (I appreciate this is a matter of taste).
> 
> Align the values by forcing the index to be always printed using
> 3 characters (enough to cover 512 in hexadecimal).
> 
> New output:
> 
> (XEN) 1ST[0x001] = 0x000000004015ff7f
> (XEN) 2ND[0x01f] = 0x00500000bfe00f7d
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

Cheers
Bertrand

> ---
> xen/arch/arm/mm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> index b42cddb1b446..c81c706c8b23 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -234,7 +234,7 @@ void dump_pt_walk(paddr_t ttbr, paddr_t addr,
> 
>         pte = mapping[offsets[level]];
> 
> -        printk("%s[0x%x] = 0x%"PRIpaddr"\n",
> +        printk("%s[0x%03x] = 0x%"PRIpaddr"\n",
>                level_strs[level], offsets[level], pte.bits);
> 
>         if ( level == 3 || !pte.walk.valid || !pte.walk.table )
> -- 
> 2.37.1
> 

[PATCH 7/8] patch arm32-tweak-enable-mmu.patch

[Julien Grall]

From: Julien Grall <jgrall@amazon.com>

---
 xen/arch/arm/arm32/head.S | 50 +++++++++++++++++++++++----------------
 1 file changed, 30 insertions(+), 20 deletions(-)

diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
index a558c2a6876e..a914ffab98a5 100644
--- a/xen/arch/arm/arm32/head.S
+++ b/xen/arch/arm/arm32/head.S
@@ -167,19 +167,12 @@ past_zImage:
         bl    check_cpu_mode
         bl    cpu_init
         bl    create_page_tables
-        bl    enable_mmu
 
-        /* We are still in the 1:1 mapping. Jump to the runtime Virtual Address. */
-        ldr   r0, =primary_switched
-        mov   pc, r0
+        /* Address in the runtime mapping to jump to after the MMU is enabled */
+        mov_w lr, primary_switched
+        b     enable_mmu
+
 primary_switched:
-        /*
-         * The 1:1 map may clash with other parts of the Xen virtual memory
-         * layout. As it is not used anymore, remove it completely to
-         * avoid having to worry about replacing existing mapping
-         * afterwards.
-         */
-        bl    remove_identity_mapping
         bl    setup_fixmap
 #ifdef CONFIG_EARLY_PRINTK
         /* Use a virtual address to access the UART. */
@@ -223,12 +216,10 @@ GLOBAL(init_secondary)
         bl    check_cpu_mode
         bl    cpu_init
         bl    create_page_tables
-        bl    enable_mmu
-
 
-        /* We are still in the 1:1 mapping. Jump to the runtime Virtual Address. */
-        ldr   r0, =secondary_switched
-        mov   pc, r0
+        /* Address in the runtime mapping to jump to after the MMU is enabled */
+        mov_w lr, secondary_switched
+        b     enable_mmu
 secondary_switched:
         /*
          * Non-boot CPUs need to move on to the proper pagetables, which were
@@ -523,9 +514,11 @@ virtphys_clash:
 ENDPROC(create_page_tables)
 
 /*
- * Turn on the Data Cache and the MMU. The function will return on the 1:1
- * mapping. In other word, the caller is responsible to switch to the runtime
- * mapping.
+ * Turn on the Data Cache and the MMU. The function will return
+ * to the virtual address provided in LR (e.g. the runtime mapping).
+ *
+ * Inputs:
+ *   lr : Virtual address to return to
  *
  * Clobbers r0 - r3
  */
@@ -551,7 +544,24 @@ enable_mmu:
         dsb                          /* Flush PTE writes and finish reads */
         mcr   CP32(r0, HSCTLR)       /* now paging is enabled */
         isb                          /* Now, flush the icache */
-        mov   pc, lr
+
+        /*
+         * The MMU is turned on and we are in the 1:1 mapping. Switch
+         * to the runtime mapping.
+         */
+        mov_w r0, 1f
+        mov   pc, r0
+1:
+        /*
+         * The 1:1 map may clash with other parts of the Xen virtual memory
+         * layout. As it is not used anymore, remove it completely to
+         * avoid having to worry about replacing existing mapping
+         * afterwards.
+         *
+         * On return this will jump to the virtual address requested by
+         * the caller.
+         */
+        b     remove_identity_mapping
 ENDPROC(enable_mmu)
 
 /*
-- 
2.37.1

[PATCH 7/7] xen/arm32: traps: Dump more information for hypervisor data abort

[Julien Grall]

From: Julien Grall <jgrall@amazon.com>

Unlike arm64, on arm32 there are no extra information dumped (e.g.
page table walk) for hypervisor data abort.

For data abort, the HSR will be set properly and so replace the call
to do_unexpected_trap() with do_trap_hyp_sync() to dispatch the error.

Signed-off-by: Julien Grall <jgrall@amazon.com>
---
 xen/arch/arm/arm32/traps.c       | 2 +-
 xen/arch/arm/include/asm/traps.h | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/arm32/traps.c b/xen/arch/arm/arm32/traps.c
index a4ce2b92d904..a2fc1c22cbc9 100644
--- a/xen/arch/arm/arm32/traps.c
+++ b/xen/arch/arm/arm32/traps.c
@@ -81,7 +81,7 @@ void do_trap_data_abort(struct cpu_user_regs *regs)
     if ( VABORT_GEN_BY_GUEST(regs) )
         do_trap_guest_serror(regs);
     else
-        do_unexpected_trap("Data Abort", regs);
+        do_trap_hyp_sync(regs);
 }
 
 void finalize_instr_emulation(const struct instr_details *instr)
diff --git a/xen/arch/arm/include/asm/traps.h b/xen/arch/arm/include/asm/traps.h
index 08bc0b484c75..883dae368eac 100644
--- a/xen/arch/arm/include/asm/traps.h
+++ b/xen/arch/arm/include/asm/traps.h
@@ -73,6 +73,7 @@ int do_bug_frame(const struct cpu_user_regs *regs, vaddr_t pc);
 
 void noreturn do_unexpected_trap(const char *msg,
                                  const struct cpu_user_regs *regs);
+void do_trap_hyp_sync(struct cpu_user_regs *regs);
 
 /* Functions for pending virtual abort checking window. */
 void abort_guest_exit_start(void);
-- 
2.37.1

RE: [PATCH 7/7] xen/arm32: traps: Dump more information for hypervisor data abort

[Henry Wang]

Hi Julien,

> -----Original Message-----
> Subject: [PATCH 7/7] xen/arm32: traps: Dump more information for
> hypervisor data abort
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> Unlike arm64, on arm32 there are no extra information dumped (e.g.
> page table walk) for hypervisor data abort.
> 
> For data abort, the HSR will be set properly and so replace the call
> to do_unexpected_trap() with do_trap_hyp_sync() to dispatch the error.
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>

I think this patch looks good to me so:

Reviewed-by: Henry Wang <Henry.Wang@arm.com>

But it seems that there is a duplicated patch at:
https://patchwork.kernel.org/project/xen-devel/patch/20220812192448.43016-10-julien@xen.org/

Kind regards,
Henry

Re: [PATCH 7/7] xen/arm32: traps: Dump more information for hypervisor data abort

[Julien Grall]

On 15/08/2022 02:40, Henry Wang wrote:
> Hi Julien,

Hi Henry,

>> -----Original Message-----
>> Subject: [PATCH 7/7] xen/arm32: traps: Dump more information for
>> hypervisor data abort
>>
>> From: Julien Grall <jgrall@amazon.com>
>>
>> Unlike arm64, on arm32 there are no extra information dumped (e.g.
>> page table walk) for hypervisor data abort.
>>
>> For data abort, the HSR will be set properly and so replace the call
>> to do_unexpected_trap() with do_trap_hyp_sync() to dispatch the error.
>>
>> Signed-off-by: Julien Grall <jgrall@amazon.com>
> 
> I think this patch looks good to me so:
> 
> Reviewed-by: Henry Wang <Henry.Wang@arm.com>
> 
> But it seems that there is a duplicated patch at:
> https://patchwork.kernel.org/project/xen-devel/patch/20220812192448.43016-10-julien@xen.org/

Hmmm... I dropped a patch from the series and it looks like I didn't 
properly clean the directory before doing that. Please ignore patch #8.

Cheers,

-- 
Julien Grall

RE: [PATCH 7/7] xen/arm32: traps: Dump more information for hypervisor data abort

[Henry Wang]

Hi Julien,

> -----Original Message-----
> From: Julien Grall <julien@xen.org>
> Subject: Re: [PATCH 7/7] xen/arm32: traps: Dump more information for
> hypervisor data abort
> Hmmm... I dropped a patch from the series and it looks like I didn't
> properly clean the directory before doing that. Please ignore patch #8.

Sure, I guess the patch that you dropped is this one?
https://patchwork.kernel.org/project/xen-devel/patch/20220812192448.43016-8-julien@xen.org/

Kind regards,
Henry

> 
> Cheers,
> 
> --
> Julien Grall

Re: [PATCH 7/7] xen/arm32: traps: Dump more information for hypervisor data abort

[Julien Grall]

On 16/08/2022 04:29, Henry Wang wrote:
> Hi Julien,

Hi Henry,

Sorry for the late reply.

> 
>> -----Original Message-----
>> From: Julien Grall <julien@xen.org>
>> Subject: Re: [PATCH 7/7] xen/arm32: traps: Dump more information for
>> hypervisor data abort
>> Hmmm... I dropped a patch from the series and it looks like I didn't
>> properly clean the directory before doing that. Please ignore patch #8.
> 
> Sure, I guess the patch that you dropped is this one?
> https://patchwork.kernel.org/project/xen-devel/patch/20220812192448.43016-8-julien@xen.org/

That's correct.

Cheers,

-- 
Julien Grall

Re: [PATCH 7/7] xen/arm32: traps: Dump more information for hypervisor data abort

[Bertrand Marquis]

Hi Julien,

> On 12 Aug 2022, at 20:24, Julien Grall <julien@xen.org> wrote:
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> Unlike arm64, on arm32 there are no extra information dumped (e.g.
> page table walk) for hypervisor data abort.

The code in arch/arm/traps.c has nothing arm32 specific like that so
could you explain this statement ?

Here the arm32 code will call the generic function which has only
something specific for BRK handling but the rest is generic.

> 
> For data abort, the HSR will be set properly and so replace the call
> to do_unexpected_trap() with do_trap_hyp_sync() to dispatch the error.

I agree with that, I just do not understand your previous statement here.

Cheers
Bertrand


> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
> ---
> xen/arch/arm/arm32/traps.c       | 2 +-
> xen/arch/arm/include/asm/traps.h | 1 +
> 2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/arm32/traps.c b/xen/arch/arm/arm32/traps.c
> index a4ce2b92d904..a2fc1c22cbc9 100644
> --- a/xen/arch/arm/arm32/traps.c
> +++ b/xen/arch/arm/arm32/traps.c
> @@ -81,7 +81,7 @@ void do_trap_data_abort(struct cpu_user_regs *regs)
>     if ( VABORT_GEN_BY_GUEST(regs) )
>         do_trap_guest_serror(regs);
>     else
> -        do_unexpected_trap("Data Abort", regs);
> +        do_trap_hyp_sync(regs);
> }
> 
> void finalize_instr_emulation(const struct instr_details *instr)
> diff --git a/xen/arch/arm/include/asm/traps.h b/xen/arch/arm/include/asm/traps.h
> index 08bc0b484c75..883dae368eac 100644
> --- a/xen/arch/arm/include/asm/traps.h
> +++ b/xen/arch/arm/include/asm/traps.h
> @@ -73,6 +73,7 @@ int do_bug_frame(const struct cpu_user_regs *regs, vaddr_t pc);
> 
> void noreturn do_unexpected_trap(const char *msg,
>                                  const struct cpu_user_regs *regs);
> +void do_trap_hyp_sync(struct cpu_user_regs *regs);
> 
> /* Functions for pending virtual abort checking window. */
> void abort_guest_exit_start(void);
> -- 
> 2.37.1
> 

Re: [PATCH 7/7] xen/arm32: traps: Dump more information for hypervisor data abort

[Julien Grall]

On 15/08/2022 17:39, Bertrand Marquis wrote:
> Hi Julien,

Hi Bertrand,

>> On 12 Aug 2022, at 20:24, Julien Grall <julien@xen.org> wrote:
>>
>> From: Julien Grall <jgrall@amazon.com>
>>
>> Unlike arm64, on arm32 there are no extra information dumped (e.g.
>> page table walk) for hypervisor data abort.
> 
> The code in arch/arm/traps.c has nothing arm32 specific like that so
> could you explain this statement ?
> 
> Here the arm32 code will call the generic function which has only
> something specific for BRK handling but the rest is generic.

The statement is not related to the code but the console output. On 
arm64, a data abort will decode the HSR and provide a dump of the 
page-table walk.

This doesn't happen on arm32 because Xen will call do_unexpected_trap(). 
So the only information we have is the HSR and FAR. This is not very 
helpful for debugging page-table walk.

After this patch, the same information will be printed on arm32 and arm64.

Cheers,

-- 
Julien Grall

Re: [PATCH 7/7] xen/arm32: traps: Dump more information for hypervisor data abort

[Bertrand Marquis]

Hi Julien,

> On 15 Aug 2022, at 18:04, Julien Grall <julien@xen.org> wrote:
> 
> 
> 
> On 15/08/2022 17:39, Bertrand Marquis wrote:
>> Hi Julien,
> 
> Hi Bertrand,
> 
>>> On 12 Aug 2022, at 20:24, Julien Grall <julien@xen.org> wrote:
>>> 
>>> From: Julien Grall <jgrall@amazon.com>
>>> 
>>> Unlike arm64, on arm32 there are no extra information dumped (e.g.
>>> page table walk) for hypervisor data abort.
>> The code in arch/arm/traps.c has nothing arm32 specific like that so
>> could you explain this statement ?
>> Here the arm32 code will call the generic function which has only
>> something specific for BRK handling but the rest is generic.
> 
> The statement is not related to the code but the console output. On arm64, a data abort will decode the HSR and provide a dump of the page-table walk.
> 
> This doesn't happen on arm32 because Xen will call do_unexpected_trap(). So the only information we have is the HSR and FAR. This is not very helpful for debugging page-table walk.
> 
> After this patch, the same information will be printed on arm32 and arm64.

Ok then this is what I understood. Your commit message is maybe a bit unclear.

I would add a sentence like that: Call do_trap_hyp_sync for hypervisor data aborts on arm32 to have the same information than on arm64.

This can be done on commit so feel free to add my:

Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

Cheers
Bertrand

> 
> Cheers,
> 
> -- 
> Julien Grall

Re: [PATCH 7/7] xen/arm32: traps: Dump more information for hypervisor data abort

[Julien Grall]

On 16/08/2022 08:28, Bertrand Marquis wrote:
> Hi Julien,

Hi Bertrand,


>> On 15 Aug 2022, at 18:04, Julien Grall <julien@xen.org> wrote:
>>
>>
>>
>> On 15/08/2022 17:39, Bertrand Marquis wrote:
>>> Hi Julien,
>>
>> Hi Bertrand,
>>
>>>> On 12 Aug 2022, at 20:24, Julien Grall <julien@xen.org> wrote:
>>>>
>>>> From: Julien Grall <jgrall@amazon.com>
>>>>
>>>> Unlike arm64, on arm32 there are no extra information dumped (e.g.
>>>> page table walk) for hypervisor data abort.
>>> The code in arch/arm/traps.c has nothing arm32 specific like that so
>>> could you explain this statement ?
>>> Here the arm32 code will call the generic function which has only
>>> something specific for BRK handling but the rest is generic.
>>
>> The statement is not related to the code but the console output. On arm64, a data abort will decode the HSR and provide a dump of the page-table walk.
>>
>> This doesn't happen on arm32 because Xen will call do_unexpected_trap(). So the only information we have is the HSR and FAR. This is not very helpful for debugging page-table walk.
>>
>> After this patch, the same information will be printed on arm32 and arm64.
> 
> Ok then this is what I understood. Your commit message is maybe a bit unclear.
> 
> I would add a sentence like that: Call do_trap_hyp_sync for hypervisor data aborts on arm32 to have the same information than on arm64.

Below the new commit message:

     Unlike arm64, on arm32 there are no extra information dumped (e.g.
     page table walk) for hypervisor data abort.

     For data abort, the HSR will be set properly and so call
     do_trap_hyp_sync() instead of do_unexpected_trap() on arm32 to have
     the print the same information as arm64.


> 
> This can be done on commit so feel free to add my:
> 
> Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

Thanks! I have committed the series.

Cheers,

-- 
Julien Grall

[PATCH 8/8] xen/arm32: traps: Dump more information for hypervisor data abort

[Julien Grall]

From: Julien Grall <jgrall@amazon.com>

Unlike arm64, on arm32 there are no extra information dumped (e.g.
page table walk) for hypervisor data abort.

For data abort, the HSR will be set properly and so replace the call
to do_unexpected_trap() with do_trap_hyp_sync() to dispatch the error.

Signed-off-by: Julien Grall <jgrall@amazon.com>
---
 xen/arch/arm/arm32/traps.c       | 2 +-
 xen/arch/arm/include/asm/traps.h | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/arm32/traps.c b/xen/arch/arm/arm32/traps.c
index a4ce2b92d904..a2fc1c22cbc9 100644
--- a/xen/arch/arm/arm32/traps.c
+++ b/xen/arch/arm/arm32/traps.c
@@ -81,7 +81,7 @@ void do_trap_data_abort(struct cpu_user_regs *regs)
     if ( VABORT_GEN_BY_GUEST(regs) )
         do_trap_guest_serror(regs);
     else
-        do_unexpected_trap("Data Abort", regs);
+        do_trap_hyp_sync(regs);
 }
 
 void finalize_instr_emulation(const struct instr_details *instr)
diff --git a/xen/arch/arm/include/asm/traps.h b/xen/arch/arm/include/asm/traps.h
index 08bc0b484c75..883dae368eac 100644
--- a/xen/arch/arm/include/asm/traps.h
+++ b/xen/arch/arm/include/asm/traps.h
@@ -73,6 +73,7 @@ int do_bug_frame(const struct cpu_user_regs *regs, vaddr_t pc);
 
 void noreturn do_unexpected_trap(const char *msg,
                                  const struct cpu_user_regs *regs);
+void do_trap_hyp_sync(struct cpu_user_regs *regs);
 
 /* Functions for pending virtual abort checking window. */
 void abort_guest_exit_start(void);
-- 
2.37.1

Re: [PATCH 8/8] xen/arm32: traps: Dump more information for hypervisor data abort

[Julien Grall]

Hi all,

Please ignore this patch. This is a duplication of patch #7.

Cheers,

On 12/08/2022 20:24, Julien Grall wrote:
> From: Julien Grall <jgrall@amazon.com>
> 
> Unlike arm64, on arm32 there are no extra information dumped (e.g.
> page table walk) for hypervisor data abort.
> 
> For data abort, the HSR will be set properly and so replace the call
> to do_unexpected_trap() with do_trap_hyp_sync() to dispatch the error.
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
> ---
>   xen/arch/arm/arm32/traps.c       | 2 +-
>   xen/arch/arm/include/asm/traps.h | 1 +
>   2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/arm32/traps.c b/xen/arch/arm/arm32/traps.c
> index a4ce2b92d904..a2fc1c22cbc9 100644
> --- a/xen/arch/arm/arm32/traps.c
> +++ b/xen/arch/arm/arm32/traps.c
> @@ -81,7 +81,7 @@ void do_trap_data_abort(struct cpu_user_regs *regs)
>       if ( VABORT_GEN_BY_GUEST(regs) )
>           do_trap_guest_serror(regs);
>       else
> -        do_unexpected_trap("Data Abort", regs);
> +        do_trap_hyp_sync(regs);
>   }
>   
>   void finalize_instr_emulation(const struct instr_details *instr)
> diff --git a/xen/arch/arm/include/asm/traps.h b/xen/arch/arm/include/asm/traps.h
> index 08bc0b484c75..883dae368eac 100644
> --- a/xen/arch/arm/include/asm/traps.h
> +++ b/xen/arch/arm/include/asm/traps.h
> @@ -73,6 +73,7 @@ int do_bug_frame(const struct cpu_user_regs *regs, vaddr_t pc);
>   
>   void noreturn do_unexpected_trap(const char *msg,
>                                    const struct cpu_user_regs *regs);
> +void do_trap_hyp_sync(struct cpu_user_regs *regs);
>   
>   /* Functions for pending virtual abort checking window. */
>   void abort_guest_exit_start(void);

-- 
Julien Grall