kernel.git/arch/arm/mm/context.c, branch linux-3.11.y

ARM: 7789/1: Do not run dummy_flush_tlb_a15_erratum() on non-Cortex-A15

2013-07-26T11:02:09Z

Commit 93dc688 (ARM: 7684/1: errata: Workaround for Cortex-A15 erratum 798181 (TLBI/DSB operations)) causes the following undefined instruction error on a mx53 (Cortex-A8): Internal error: Oops - undefined instruction: 0 [#1] SMP ARM CPU: 0 PID: 275 Comm: modprobe Not tainted 3.11.0-rc2-next-20130722-00009-g9b0f371 #881 task: df46cc00 ti: df48e000 task.ti: df48e000 PC is at check_and_switch_context+0x17c/0x4d0 LR is at check_and_switch_context+0xdc/0x4d0 This problem happens because check_and_switch_context() calls dummy_flush_tlb_a15_erratum() without checking if we are really running on a Cortex-A15 or not. To avoid this issue, only call dummy_flush_tlb_a15_erratum() inside check_and_switch_context() if erratum_a15_798181() returns true, which means that we are really running on a Cortex-A15. Signed-off-by: Fabio Estevam Acked-by: Catalin Marinas Reviewed-by: Roger Quadros Signed-off-by: Russell King

Merge branch 'devel-stable' into for-next

2013-06-29T10:44:43Z

Conflicts: arch/arm/Makefile arch/arm/include/asm/glue-proc.h

ARM: 7769/1: Cortex-A15: fix erratum 798181 implementation

2013-06-24T14:27:35Z

Looking into the active_asids array is not enough, as we also need to look into the reserved_asids array (they both represent processes that are currently running). Also, not holding the ASID allocator lock is racy, as another CPU could schedule that process and trigger a rollover, making the erratum workaround miss an IPI. Exposing this outside of context.c is a little ugly on the side, so let's define a new entry point that the erratum workaround can call to obtain the cpumask. Cc: # 3.9 Acked-by: Will Deacon Acked-by: Catalin Marinas Signed-off-by: Marc Zyngier Signed-off-by: Russell King

ARM: 7768/1: prevent risks of out-of-bound access in ASID allocator

2013-06-24T14:26:41Z

On a CPU that never ran anything, both the active and reserved ASID fields are set to zero. In this case the ASID_TO_IDX() macro will return -1, which is not a very useful value to index a bitmap. Instead of trying to offset the ASID so that ASID #1 is actually bit 0 in the asid_map bitmap, just always ignore bit 0 and start the search from bit 1. This makes the code a bit more readable, and without risk of OoB access. Cc: # 3.9 Acked-by: Will Deacon Acked-by: Catalin Marinas Reported-by: Catalin Marinas Signed-off-by: Marc Zyngier Signed-off-by: Russell King

ARM: 7767/1: let the ASID allocator handle suspended animation

2013-06-24T14:24:54Z

When a CPU is running a process, the ASID for that process is held in a per-CPU variable (the "active ASIDs" array). When the ASID allocator handles a rollover, it copies the active ASIDs into a "reserved ASIDs" array to ensure that a process currently running on another CPU will continue to run unaffected. The active array is zero-ed to indicate that a rollover occurred. Because of this mechanism, a reserved ASID is only remembered for a single rollover. A subsequent rollover will completely refill the reserved ASIDs array. In a severely oversubscribed environment where a CPU can be prevented from running for extended periods of time (think virtual machines), the above has a horrible side effect: [P{a} denotes process P running with ASID a] CPU-0 CPU-1 A{x} [active = ] [suspended] runs B{y} [active = ] [rollover: active = <0 0> reserved = ] runs B{y} [active = <0 y> reserved = ] [rollover: active = <0 0> reserved = <0 y>] runs C{x} [active = <0 x>] [resumes] runs A{x} At that stage, both A and C have the same ASID, with deadly consequences. The fix is to preserve reserved ASIDs across rollovers if the CPU doesn't have an active ASID when the rollover occurs. Cc: # 3.9 Acked-by: Will Deacon Acked-by: Catalin Carinas Signed-off-by: Marc Zyngier Signed-off-by: Russell King

ARM: LPAE: use 64-bit accessors for TTBR registers

2013-05-30T15:02:07Z

This patch adds TTBR accessor macros, and modifies cpu_get_pgd() and the LPAE version of cpu_set_reserved_ttbr0() to use these instead. In the process, we also fix these functions to correctly handle cases where the physical address lies beyond the 4G limit of 32-bit addressing. Signed-off-by: Cyril Chemparathy Signed-off-by: Vitaly Andrianov Acked-by: Nicolas Pitre Reviewed-by: Catalin Marinas Tested-by: Santosh Shilimkar Tested-by: Subash Patel Signed-off-by: Will Deacon

ARM: 7684/1: errata: Workaround for Cortex-A15 erratum 798181 (TLBI/DSB operations)

2013-04-03T15:45:49Z

On Cortex-A15 (r0p0..r3p2) the TLBI/DSB are not adequately shooting down all use of the old entries. This patch implements the erratum workaround which consists of: 1. Dummy TLBIMVAIS and DSB on the CPU doing the TLBI operation. 2. Send IPI to the CPUs that are running the same mm (and ASID) as the one being invalidated (or all the online CPUs for global pages). 3. CPU receiving the IPI executes a DMB and CLREX (part of the exception return code already). Signed-off-by: Catalin Marinas Signed-off-by: Russell King

ARM: 7661/1: mm: perform explicit branch predictor maintenance when required

2013-03-03T22:54:16Z

The ARM ARM requires branch predictor maintenance if, for a given ASID, the instructions at a specific virtual address appear to change. From the kernel's point of view, that means: - Changing the kernel's view of memory (e.g. switching to the identity map) - ASID rollover (since ASIDs will be re-allocated to new tasks) This patch adds explicit branch predictor maintenance when either of the two conditions above are met. Reviewed-by: Catalin Marinas Signed-off-by: Will Deacon Signed-off-by: Russell King

ARM: 7659/1: mm: make mm->context.id an atomic64_t variable

2013-03-03T22:54:14Z

mm->context.id is updated under asid_lock when a new ASID is allocated to an mm_struct. However, it is also read without the lock when a task is being scheduled and checking whether or not the current ASID generation is up-to-date. If two threads of the same process are being scheduled in parallel and the bottom bits of the generation in their mm->context.id match the current generation (that is, the mm_struct has not been used for ~2^24 rollovers) then the non-atomic, lockless access to mm->context.id may yield the incorrect ASID. This patch fixes this issue by making mm->context.id and atomic64_t, ensuring that the generation is always read consistently. For code that only requires access to the ASID bits (e.g. TLB flushing by mm), then the value is accessed directly, which GCC converts to an ldrb. Cc: # 3.8 Reviewed-by: Catalin Marinas Signed-off-by: Will Deacon Signed-off-by: Russell King

ARM: 7658/1: mm: fix race updating mm->context.id on ASID rollover

2013-03-03T22:54:13Z

If a thread triggers an ASID rollover, other threads of the same process must be made to wait until the mm->context.id for the shared mm_struct has been updated to new generation and associated book-keeping (e.g. TLB invalidation) has ben performed. However, there is a *tiny* window where both mm->context.id and the relevant active_asids entry are updated to the new generation, but the TLB flush has not been performed, which could allow another thread to return to userspace with a dirty TLB, potentially leading to data corruption. In reality this will never occur because one CPU would need to perform a context-switch in the time it takes another to do a couple of atomic test/set operations but we should plug the race anyway. This patch moves the active_asids update until after the potential TLB flush on context-switch. Cc: # 3.8 Reviewed-by: Catalin Marinas Signed-off-by: Will Deacon Signed-off-by: Russell King