[XEN,v4] xen/arm32: head: Replace load_paddr with adr_l when they are equivalent

Commit Message

Ayan Kumar Halder Nov. 2, 2023, 7:46 p.m. UTC

Before the MMU is turned on, PC uses physical address. Thus, one can use adr_l
instead of load_paddr to obtain the physical address of a symbol.

The only exception (for this replacement) is create_table_entry() which is
called before and after MMU is turned on.

Also, in lookup_processor_type() "r10" is no longer used. The reason being
__lookup_processor_type uses adr_l (thus r10 is no longer used to obtain the
physical address offset). Consequently, there is no need to save/restore r10.

Signed-off-by: Ayan Kumar Halder <[e-mail]>
Reviewed-by: Michal Orzel <[e-mail]>
---

Refer https://lists.archive.carbon60.com/xen/devel/682900 for details.

Changes from :-

v1 :- 1. No need to modify create_table_entry().
2. Remove "mov   r10, #0 " in lookup_processor_type().

v2 :- 1. No need to save/restore r10 in lookup_processor_type().
2. Update the commit message title.

v3 :- 1. In __lookup_processor_type(), update the comment.
Add Michal's R-b.

 xen/arch/arm/arm32/head.S | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

Patch

diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
index 33b038e7e0..20e92bdb61 100644
--- a/xen/arch/arm/arm32/head.S
+++ b/xen/arch/arm/arm32/head.S
@@ -171,7 +171,7 @@  past_zImage:
 
         /* Using the DTB in the .dtb section? */
 .ifnes CONFIG_DTB_FILE,""
-        load_paddr r8, _sdtb
+        adr_l r8, _sdtb
 .endif
 
         /* Initialize the UART if earlyprintk has been enabled. */
@@ -213,7 +213,7 @@  GLOBAL(init_secondary)
         mrc   CP32(r1, MPIDR)
         bic   r7, r1, #(~MPIDR_HWID_MASK) /* Mask out flags to get CPU ID */
 
-        load_paddr r0, smp_up_cpu
+        adr_l r0, smp_up_cpu
         dsb
 2:      ldr   r1, [r0]
         cmp   r1, r7
@@ -479,7 +479,7 @@  create_page_tables:
          * create_table_entry_paddr() will clobber the register storing
          * the physical address of the table to point to.
          */
-        load_paddr r5, boot_third
+        adr_l r5, boot_third
         mov_w r4, XEN_VIRT_START
 .rept XEN_NR_ENTRIES(2)
         mov   r0, r5                        /* r0 := paddr(l3 table) */
@@ -578,7 +578,7 @@  enable_mmu:
         flush_xen_tlb_local r0
 
         /* Write Xen's PT's paddr into the HTTBR */
-        load_paddr r0, boot_pgtable
+        adr_l r0, boot_pgtable
         mov   r1, #0                 /* r0:r1 is paddr (boot_pagetable) */
         mcrr  CP64(r0, r1, HTTBR)
         isb
@@ -876,19 +876,14 @@  putn:   mov   pc, lr
 
 /* This provides a C-API version of __lookup_processor_type */
 ENTRY(lookup_processor_type)
-        stmfd sp!, {r4, r10, lr}
-        mov   r10, #0                   /* r10 := offset between virt&phys */
+        stmfd sp!, {r4, lr}
         bl    __lookup_processor_type
         mov r0, r1
-        ldmfd sp!, {r4, r10, pc}
+        ldmfd sp!, {r4, pc}
 
 /*
  *  Read processor ID register (CP#15, CR0), and Look up in the linker-built
- * supported processor list. Note that we can't use the absolute addresses for
- * the __proc_info lists since we aren't running with the MMU on (and therefore,
- * we are not in correct address space). We have to calculate the offset.
- *
- * r10: offset between virt&phys
+ * supported processor list.
  *
  * Returns:
  * r0: CPUID
@@ -897,8 +892,8 @@  ENTRY(lookup_processor_type)
  */
 __lookup_processor_type:
         mrc   CP32(r0, MIDR)                /* r0 := our cpu id */
-        load_paddr r1, __proc_info_start
-        load_paddr r2, __proc_info_end
+        adr_l r1, __proc_info_start
+        adr_l r2, __proc_info_end
 1:      ldr   r3, [r1, #PROCINFO_cpu_mask]
         and   r4, r0, r3                    /* r4 := our cpu id with mask */
         ldr   r3, [r1, #PROCINFO_cpu_val]   /* r3 := cpu val in current proc info */