kernel/linux.git/arch/mips/include/asm/mmu_context.h, branch linux-4.4.y

MIPS: HTW: Prevent accidental HTW start due to nested htw_{start, stop}

2015-02-16T09:55:26+00:00

activate_mm() and switch_mm() call get_new_mmu_context() which in turn can enable the HTW before the entryhi is changed with the new ASID. Since the latter will enable the HTW in local_flush_tlb_all(), then there is a small timing window where the HTW is running with the new ASID but with an old pgd since the TLBMISS_HANDLER_SETUP_PGD hasn't assigned a new one yet. In order to prevent that, we introduce a simple htw counter to avoid starting HTW accidentally due to nested htw_{start,stop}() sequences. Moreover, since various IPI calls can enforce TLB flushing operations on a different core, such an operation may interrupt another htw_{stop,start} in progress leading inconsistent updates of the htw_seq variable. In order to avoid that, we disable the interrupts whenever we update that variable. Signed-off-by: Markos Chandras Cc: # 3.17+ Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/9118/ Signed-off-by: Ralf Baechle

MIPS,prctl: add PR_[GS]ET_FP_MODE prctl options for MIPS

2015-02-12T11:30:29+00:00

Userland code may be built using an ABI which permits linking to objects that have more restrictive floating point requirements. For example, userland code may be built to target the O32 FPXX ABI. Such code may be linked with other FPXX code, or code built for either one of the more restrictive FP32 or FP64. When linking with more restrictive code, the overall requirement of the process becomes that of the more restrictive code. The kernel has no way to know in advance which mode the process will need to be executed in, and indeed it may need to change during execution. The dynamic loader is the only code which will know the overall required mode, and so it needs to have a means to instruct the kernel to switch the FP mode of the process. This patch introduces 2 new options to the prctl syscall which provide such a capability. The FP mode of the process is represented as a simple bitmask combining a number of mode bits mirroring those present in the hardware. Userland can either retrieve the current FP mode of the process: mode = prctl(PR_GET_FP_MODE); or modify the current FP mode of the process: err = prctl(PR_SET_FP_MODE, new_mode); Signed-off-by: Paul Burton Cc: Matthew Fortune Cc: Markos Chandras Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/8899/ Signed-off-by: Ralf Baechle

MIPS: mm: Use the Hardware Page Table Walker if the core supports it

2014-08-01T22:06:39+00:00

The Hardware Page Table Walker aims to speed up TLB refill exceptions by handling them in the hardware level instead of having a software TLB refill handler. However, a TLB refill exception can still be thrown in certain cases such as, synchronus exceptions, or address translation or memory errors during the HTW operation. As a result of which, HTW must not be considered a complete replacement for the TLB refill software handler, but rather a fast-path for it. For HTW to work, the PWBase register must contain the task's page global directory address so the HTW will kick in on TLB refill exceptions. Due to HTW being a separate engine embedded deep in the CPU pipeline, we need to restart the HTW everytime a PTE changes to avoid HTW fetching a old entry from the page tables. It's also necessary to restart the HTW on context switches to prevent it from fetching a page from the previous process. Finally, since HTW is using the entryhi register to write the translations to the TLB, it's necessary to stop the HTW whenever the entryhi changes (eg for tlb probe perations) and enable it back afterwards. == Performance == The following trivial test was used to measure the performance of the HTW. Using the same root filesystem, the following command was used to measure the number of tlb refill handler executions with and without (using 'nohtw' kernel parameter) HTW support. The kernel was modified to use a scratch register as a counter for the TLB refill exceptions. find /usr -type f -exec ls -lh {} \; HTW Enabled: TLB refill exceptions: 12306 HTW Disabled: TLB refill exceptions: 17805 Signed-off-by: Markos Chandras Cc: linux-mips@linux-mips.org Cc: Markos Chandras Patchwork: https://patchwork.linux-mips.org/patch/7336/ Signed-off-by: Ralf Baechle

Merge branch 'wip-mips-pm' of https://github.com/paulburton/linux into mips-for-linux-next

2014-05-29T13:08:23+00:00

MIPS: MT: Remove SMTC support

2014-05-23T22:07:01+00:00

Nobody is maintaining SMTC anymore and there also seems to be no userbase. Which is a pity - the SMTC technology primarily developed by Kevin D. Kissell is an ingenious demonstration for the MT ASE's power and elegance. Based on Markos Chandras patch https://patchwork.linux-mips.org/patch/6719/ which while very similar did no longer apply cleanly when I tried to merge it plus some additional post-SMTC cleanup - SMTC was a feature as tricky to remove as it was to merge once upon a time. Signed-off-by: Ralf Baechle

MIPS: traps: Add CPU PM callback for trap configuration

2014-05-02T15:38:59+00:00

Implement a CPU power management callback for restoring trap related CPU configuration after CPU power up from a low power state. The following state is restored: - Status register - HWREna register - Exception vector configuration registers - Context/XContext register Signed-off-by: James Hogan Signed-off-by: Paul Burton

MIPS: mm: Use scratch for PGD when !CONFIG_MIPS_PGD_C0_CONTEXT

2013-10-29T20:24:51+00:00

Allow usage of scratch register for current pgd even when MIPS_PGD_C0_CONTEXT is not configured. MIPS_PGD_C0_CONTEXT is set for 64r2 platforms to indicate availability of Xcontext for saving cpuid, thus freeing Context to be used for saving PGD. This option was also tied to using a scratch register for storing PGD. This commit will allow usage of scratch register to store the current pgd if one can be allocated for the platform, even when MIPS_PGD_C0_CONTEXT is not set. The cpuid will be kept in the CP0 Context register in this case. The code to store the current pgd for the TLB miss handler is now generated in all cases. When scratch register is available, the PGD is also stored in the scratch register. Signed-off-by: Jayachandran C Cc: linux-mips@linux-mips.org Cc: Hauke Mehrtens Patchwork: https://patchwork.linux-mips.org/patch/5906/ Signed-off-by: Ralf Baechle

MIPS: Move definition of SMP processor id register to header file

2013-10-29T20:23:51+00:00

The definition of the CP0 register used to save the smp processor id is repicated in many files, move them all to thread_info.h. Signed-off-by: Jayachandran C Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/5708/ Signed-off-by: Ralf Baechle

Merge branch '3.10-fixes' into mips-for-linux-next

2013-07-12T16:11:43+00:00

This that should have been fixed but weren't, way to much, intrusive and late.

MIPS: Move generated code to .text for microMIPS

2013-07-01T13:10:56+00:00

Prepare of a next patch which will call tlbmiss_handler_setup_pgd on microMIPS. MicroMIPS complains if the called code s not in the .text section. To fix this we generate code into space reserved in arch/mips/mm/tlb-funcs.S While there, move the rest of the generated functions (handle_tlbl, handle_tlbs, handle_tlbm) to the same file. Signed-off-by: Jayachandran C Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/5542/ Signed-off-by: Ralf Baechle