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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 <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Markos Chandras <markos.chandras@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/7336/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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mips-for-linux-next
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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 <kevink@paralogos.com> is an ingenious demonstration for the MT
ASE's power and elegance.
Based on Markos Chandras <Markos.Chandras@imgtec.com> 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 <ralf@linux-mips.org>
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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 <james.hogan@imgtec.com>
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
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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 <jchandra@broadcom.com>
Cc: linux-mips@linux-mips.org
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Patchwork: https://patchwork.linux-mips.org/patch/5906/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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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 <jchandra@broadcom.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5708/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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This that should have been fixed but weren't, way to much, intrusive
and late.
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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 <jchandra@broadcom.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5542/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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The kvm_* symbols are only available if KVM is selected.
Fixes the following linking problem on a randconfig:
arch/mips/built-in.o: In function `local_flush_tlb_mm':
(.text+0x18a94): undefined reference to `kvm_local_flush_tlb_all'
arch/mips/built-in.o: In function `local_flush_tlb_range':
(.text+0x18d0c): undefined reference to `kvm_local_flush_tlb_all'
kernel/built-in.o: In function `__schedule':
core.c:(.sched.text+0x2a00): undefined reference to `kvm_local_flush_tlb_all'
mm/built-in.o: In function `use_mm':
(.text+0x30214): undefined reference to `kvm_local_flush_tlb_all'
fs/built-in.o: In function `flush_old_exec':
(.text+0xf0a0): undefined reference to `kvm_local_flush_tlb_all'
make: *** [vmlinux] Error 1
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Acked-by: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5437/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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This reverts commit d532f3d26716a39dfd4b88d687bd344fbe77e390.
The original commit has several problems:
1) Doesn't work with 64-bit kernels.
2) Calls TLBMISS_HANDLER_SETUP() before the code is generated.
3) Calls TLBMISS_HANDLER_SETUP() twice in per_cpu_trap_init() when
only one call is needed.
[ralf@linux-mips.org: Also revert the bits of the ASID patch which were
hidden in the KVM merge.]
Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: "Steven J. Hill" <Steven.Hill@imgtec.com>
Cc: David Daney <david.daney@cavium.com>
Patchwork: https://patchwork.linux-mips.org/patch/5242/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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git://git.linux-mips.org/pub/scm/sjhill/linux-sjhill into mips-for-linux-next
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Original patch by Ralf Baechle and removed by Harold Koerfgen
with commit f67e4ffc79905482c3b9b8c8dd65197bac7eb508. This
allows for more generic kernels since the size of the ASID
and corresponding masks can be determined at run-time. This
patch is also required for the new Aptiv cores and has been
tested on Malta and Malta Aptiv platforms.
[ralf@linux-mips.org: Added relevant part of fix
https://patchwork.linux-mips.org/patch/5213/]
Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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on a ASID wrap.
Signed-off-by: Sanjay Lal <sanjayl@kymasys.com>
Cc: kvm@vger.kernel.org
Cc: linux-mips@linux-mips.org
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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git://git.linux-mips.org/pub/scm/john/linux-john into mips-for-linux-next
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Currently, init_new_context() only for each online CPU, this may cause
memory corruption when CPU hotplug and fork() happens at the same time.
To avoid this, we make init_new_context() cover each possible CPU.
Scenario:
1, CPU#1 is being offline;
2, On CPU#0, do_fork() call dup_mm() and copy a mm_struct to the child;
3, On CPU#0, dup_mm() call init_new_context(), since CPU#1 is offline
and init_new_context() only covers the online CPUs, child has the
same asid as its parent on CPU#1 (however, child's asid should be 0);
4, CPU#1 is being online;
5, Now, if both parent and child run on CPU#1, memory corruption (e.g.
segfault, bus error, etc.) will occur.
Signed-off-by: Huacai Chen <chenhc@lemote.com>
Acked-by: David Daney <david.daney@cavium.com>
Patchwork: http://patchwork.linux-mips.org/patch/4995/
Acked-by: John Crispin <blogic@openwrt.org>
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tlbmiss_handler_setup_pgd is run-time generated code and it was convenient
to pretend the symbol was an array in the generator but a function for
the users. LTO gcc won't tolerate this kind of lie anymore so solve the
problem through a cast and function pointer instead.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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Having received another series of whitespace patches I decided to do this
once and for all rather than dealing with this kind of patches trickling
in forever.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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Nobody seems to be interested anymore and upstream also never had an
ethernet driver.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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It is unused in the tree.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3557/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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Decide at runtime to use either Context or KScratch to hold the PGD
pointer.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1876/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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This is a preliminary patch to add a vdso to all user processes. Still
missing are ELF headers and .eh_frame information. But it is enough to
allow us to move signal trampolines off of the stack. Note that emulation
of branch delay slots in the FPU emulator still requires the stack.
We allocate a single page (the vdso) and write all possible signal
trampolines into it. The stack is moved down by one page and the vdso is
mapped into this space.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/975/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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Processors that support the mips64r2 ISA can in four instructions
convert a shifted PGD pointer stored in the upper bits of c0_context
into a usable pointer. By doing this we save a memory load and
associated potential cache miss in the TLB exception handlers.
Since the upper bits of c0_context were holding the CPU number, we
move this to the upper bits of c0_xcontext which doesn't have enough
bits to hold the PGD pointer, but has plenty for the CPU number.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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set_saved_sp reads Context register. Avoid reading stale value from
earlier incomplete write.
Issue found and fixed for head.S by Chris Dearman <chris@mips.com>.
Signed-off-by: Chris Dearman <chris@mips.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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We've silently been relying on the hardware chopping off excess, reserved
ASID bits for no better reason that it saving an instruction. Because we
already have:
#define cpu_asid(cpu, mm) (cpu_context((cpu), (mm)) & ASID_MASK)
in <asm/mmu_context.h>.
We can use a cleanup to avoid writing non-zero bits into the reserved
entryhi bits. This avoid triggering some debugging assertion in the
Cavium simulator.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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Makes code futureproof against the impending change to mm->cpu_vm_mask.
It's also a chance to use the new cpumask_ ops which take a pointer
(the older ones are deprecated, but there's no hurry for arch code).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Some of the were relying into smp.h being dragged in by another header
which of course is fragile. <asm/cpu-info.h> uses smp_processor_id()
only in macros and including smp.h there leads to an include loop, so
don't change cpu-info.h.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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