From 52af9c6cd863fe37d1103035ec7ee22ac1296458 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Thu, 26 May 2011 11:23:43 +0100 Subject: ARM: 6943/1: mm: use TTBR1 instead of reserved context ID On ARMv7 CPUs that cache first level page table entries (like the Cortex-A15), using a reserved ASID while changing the TTBR or flushing the TLB is unsafe. This is because the CPU may cache the first level entry as the result of a speculative memory access while the reserved ASID is assigned. After the process owning the page tables dies, the memory will be reallocated and may be written with junk values which can be interpreted as global, valid PTEs by the processor. This will result in the TLB being populated with bogus global entries. This patch avoids the use of a reserved context ID in the v7 switch_mm and ASID rollover code by temporarily using the swapper_pg_dir pointed at by TTBR1, which contains only global entries that are not tagged with ASIDs. Acked-by: Catalin Marinas Signed-off-by: Will Deacon Signed-off-by: Russell King --- arch/arm/mm/proc-v7.S | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) (limited to 'arch/arm/mm/proc-v7.S') diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S index 3c3867850a30..b3b566ec83d3 100644 --- a/arch/arm/mm/proc-v7.S +++ b/arch/arm/mm/proc-v7.S @@ -108,18 +108,16 @@ ENTRY(cpu_v7_switch_mm) #ifdef CONFIG_ARM_ERRATA_430973 mcr p15, 0, r2, c7, c5, 6 @ flush BTAC/BTB #endif -#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 + mrc p15, 0, r2, c2, c0, 1 @ load TTB 1 + mcr p15, 0, r2, c2, c0, 0 @ into 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) -- cgit v1.2.3