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path: root/arch/mips/mm/context.c
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2019-02-05MIPS: Export mm switching functions used by KVMPaul Burton
KVM makes use of check_switch_mmu_context(), check_mmu_context() & get_new_mmu_context() which are no longer static inline functions in a header. As such they need to be exported for KVM to successfully build as a module, which was previously overlooked. Add the missing exports. Signed-off-by: Paul Burton <paul.burton@mips.com> Fixes: 4ebea49ce233 ("MIPS: mm: Un-inline get_new_mmu_context") Fixes: 42d5b846574f ("MIPS: mm: Unify ASID version checks")
2019-02-04MIPS: MemoryMapID (MMID) SupportPaul Burton
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 <paul.burton@mips.com> Cc: linux-mips@vger.kernel.org
2019-02-04MIPS: mm: Add set_cpu_context() for ASID assignmentsPaul Burton
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 <paul.burton@mips.com> Cc: linux-mips@vger.kernel.org
2019-02-04MIPS: mm: Unify ASID version checksPaul Burton
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 <paul.burton@mips.com> Cc: linux-mips@vger.kernel.org
2019-02-04MIPS: mm: Un-inline get_new_mmu_contextPaul Burton
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 <paul.burton@mips.com> Cc: linux-mips@vger.kernel.org