Revert "ARM: 6943/1: mm: use TTBR1 instead of reserved context ID"

This reverts commit 52af9c6cd863fe37d1103035ec7ee22ac1296458.

Will Deacon reports that:

 In 52af9c6c ("ARM: 6943/1: mm: use TTBR1 instead of reserved context ID")
 I updated the ASID rollover code to use only the kernel page tables
 whilst updating the ASID.

 Unfortunately, the code to restore the user page tables was part of a
 later patch which isn't yet in mainline, so this leaves the code
 quite broken.

We're also in the process of eliminating __ARCH_WANT_INTERRUPTS_ON_CTXSW
from ARM, so lets revert these until we can properly sort out what we're
doing with the ARM context switching.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c
index 8bfae964b133987e061c430a0426f951b07172fa..b6c776ae4039b963c88d28b1b34d9f04f8ad4e01 100644 (file)
--- a/arch/arm/mm/context.c
+++ b/arch/arm/mm/context.c
@@ -24,7 +24,9 @@ DEFINE_PER_CPU(struct mm_struct *, current_mm);
 
 /*
  * We fork()ed a process, and we need a new context for the child
- * to run in.
+ * to run in.  We reserve version 0 for initial tasks so we will
+ * always allocate an ASID. The ASID 0 is reserved for the TTBR
+ * register changing sequence.
  */
 void __init_new_context(struct task_struct *tsk, struct mm_struct *mm)
 {
@@ -34,11 +36,8 @@ void __init_new_context(struct task_struct *tsk, struct mm_struct *mm)
 
 static void flush_context(void)
 {
-       u32 ttb;
-       /* Copy TTBR1 into TTBR0 */
-       asm volatile("mrc       p15, 0, %0, c2, c0, 1\n"
-                    "mcr       p15, 0, %0, c2, c0, 0"
-                    : "=r" (ttb));
+       /* set the reserved ASID before flushing the TLB */
+       asm("mcr        p15, 0, %0, c13, c0, 1\n" : : "r" (0));
        isb();
        local_flush_tlb_all();
        if (icache_is_vivt_asid_tagged()) {

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index b3b566ec83d397c1074c1dcbee0d5e33542e7d9c..3c3867850a3011d1e163d347a25ffbabc4aa4dc7 100644 (file)
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -108,16 +108,18 @@ ENTRY(cpu_v7_switch_mm)
 #ifdef CONFIG_ARM_ERRATA_430973
        mcr     p15, 0, r2, c7, c5, 6           @ flush BTAC/BTB
 #endif
-       mrc     p15, 0, r2, c2, c0, 1           @ load TTB 1
-       mcr     p15, 0, r2, c2, c0, 0           @ into TTB 0
+#ifdef CONFIG_ARM_ERRATA_754322
+       dsb
+#endif
+       mcr     p15, 0, r2, c13, c0, 1          @ set reserved context ID
+       isb
+1:     mcr     p15, 0, r0, c2, c0, 0           @ set TTB 0
        isb
 #ifdef CONFIG_ARM_ERRATA_754322
        dsb
 #endif
        mcr     p15, 0, r1, c13, c0, 1          @ set context ID
        isb
-       mcr     p15, 0, r0, c2, c0, 0           @ set TTB 0
-       isb
 #endif
        mov     pc, lr
 ENDPROC(cpu_v7_switch_mm)