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 8bfae96..b6c776a 100644
--- a/arch/arm/mm/context.c
+++ b/arch/arm/mm/context.c
@@ -24,7 +24,9 @@
/*
* 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 @@
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 b3b566e..3c38678 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -108,16 +108,18 @@
#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)
