kernel/arch/mips/include/asm/mmu_context.h, branch linux-rolling-stable

mips: use asm-generic/mmu_context.h for no-op implementations

2020-10-27T15:02:36Z

Signed-off-by: Nicholas Piggin Acked-by: Thomas Bogendoerfer Cc: Thomas Bogendoerfer Cc: linux-mips@vger.kernel.org Signed-off-by: Arnd Bergmann

MIPS: MemoryMapID (MMID) Support

2019-02-04T18:56:41Z

Introduce support for using MemoryMapIDs (MMIDs) as an alternative to Address Space IDs (ASIDs). The major difference between the two is that MMIDs are global - ie. an MMID uniquely identifies an address space across all coherent CPUs. In contrast ASIDs are non-global per-CPU IDs, wherein each address space is allocated a separate ASID for each CPU upon which it is used. This global namespace allows a new GINVT instruction be used to globally invalidate TLB entries associated with a particular MMID across all coherent CPUs in the system, removing the need for IPIs to invalidate entries with separate ASIDs on each CPU. The allocation scheme used here is largely borrowed from arm64 (see arch/arm64/mm/context.c). In essence we maintain a bitmap to track available MMIDs, and MMIDs in active use at the time of a rollover to a new MMID version are preserved in the new version. The allocation scheme requires efficient 64 bit atomics in order to perform reasonably, so this support depends upon CONFIG_GENERIC_ATOMIC64=n (ie. currently it will only be included in MIPS64 kernels). The first, and currently only, available CPU with support for MMIDs is the MIPS I6500. This CPU supports 16 bit MMIDs, and so for now we cap our MMIDs to 16 bits wide in order to prevent the bitmap growing to absurd sizes if any future CPU does implement 32 bit MMIDs as the architecture manuals suggest is recommended. When MMIDs are in use we also make use of GINVT instruction which is available due to the global nature of MMIDs. By executing a sequence of GINVT & SYNC 0x14 instructions we can avoid the overhead of an IPI to each remote CPU in many cases. One complication is that GINVT will invalidate wired entries (in all cases apart from type 0, which targets the entire TLB). In order to avoid GINVT invalidating any wired TLB entries we set up, we make sure to create those entries using a reserved MMID (0) that we never associate with any address space. Also of note is that KVM will require further work in order to support MMIDs & GINVT, since KVM is involved in allocating IDs for guests & in configuring the MMU. That work is not part of this patch, so for now when MMIDs are in use KVM is disabled. Signed-off-by: Paul Burton Cc: linux-mips@vger.kernel.org

MIPS: mm: Add set_cpu_context() for ASID assignments

2019-02-04T18:56:33Z

When we gain MMID support we'll be storing MMIDs as atomic64_t values and accessing them via atomic64_* functions. This necessitates that we don't use cpu_context() as the left hand side of an assignment, ie. as a modifiable lvalue. In preparation for this introduce a new set_cpu_context() function & replace all assignments with cpu_context() on their left hand side with an equivalent call to set_cpu_context(). To enforce that cpu_context() should not be used for assignments, we rewrite it as a static inline function. Signed-off-by: Paul Burton Cc: linux-mips@vger.kernel.org

MIPS: mm: Unify ASID version checks

2019-02-04T18:56:30Z

Introduce a new check_mmu_context() function to check an mm's ASID version & get a new one if it's outdated, and a check_switch_mmu_context() function which additionally sets up the new ASID & page directory. Simplify switch_mm() & various get_new_mmu_context() callsites in MIPS KVM by making use of the new functions, which will help reduce the amount of code that requires modification to gain MMID support. Signed-off-by: Paul Burton Cc: linux-mips@vger.kernel.org

MIPS: mm: Un-inline get_new_mmu_context

2019-02-04T18:56:28Z

In preparation for adding MMID support to get_new_mmu_context() which will increase the size of the function somewhat, move it from asm/mmu_context.h into a C file. Signed-off-by: Paul Burton Cc: linux-mips@vger.kernel.org

MIPS: mm: Move drop_mmu_context() comment into appropriate block

2019-02-04T18:56:20Z

drop_mmu_context() is preceded by a comment indicating what happens if the mm provided is currently active on the local CPU. Move that comment into the block that executes in this case, adjusting slightly to reflect its new location. Signed-off-by: Paul Burton Cc: linux-mips@vger.kernel.org

MIPS: mm: Consolidate drop_mmu_context() has-ASID checks

2019-02-04T18:56:18Z

If an mm does not have an ASID on the local CPU then drop_mmu_context() is always redundant, since there's no context to "drop". Various callers of drop_mmu_context() check whether the mm has been allocated an ASID before making the call. Move that check into drop_mmu_context() and remove it from callers to simplify them. Signed-off-by: Paul Burton Cc: linux-mips@vger.kernel.org

MIPS: mm: Avoid HTW stop/start when dropping an inactive mm

2019-02-04T18:56:16Z

If drop_mmu_context() is called with an mm that is not currently active on the local CPU then there's no need for us to stop & start a hardware page table walker because it can't be fetching entries for the ASID corresponding to the mm we're operating on. Move the htw_stop() & htw_start() calls into the block which we run only if the mm is currently active, in order to avoid the redundant work. Signed-off-by: Paul Burton Cc: linux-mips@vger.kernel.org

MIPS: mm: Remove redundant get_new_mmu_context() cpu argument

2019-02-04T18:56:14Z

get_new_mmu_context() accepts a cpu argument, but implicitly assumes that this is always equal to smp_processor_id() by operating on the local CPU's TLB & icache. Remove the cpu argument and have get_new_mmu_context() call smp_processor_id() instead. Signed-off-by: Paul Burton Cc: linux-mips@vger.kernel.org

MIPS: mm: Remove redundant drop_mmu_context() cpu argument

2019-02-04T18:56:12Z

The drop_mmu_context() function accepts a cpu argument, but it implicitly expects that this is always equal to smp_processor_id() by allocating & configuring an ASID on the local CPU when the mm is active on the CPU indicated by the cpu argument. All callers do provide the value of smp_processor_id() to the cpu argument. Remove the redundant argument and have drop_mmu_context() call smp_processor_id() itself, making it clearer that the cpu variable always represents the local CPU. Signed-off-by: Paul Burton Cc: linux-mips@vger.kernel.org