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  1. 13 Dec, 2018 1 commit
    • Firoz Khan's avatar
      mips: add __NR_syscalls along with __NR_Linux_syscalls · ef2512c8
      Firoz Khan authored 
      __NR_Linux_syscalls macro holds the number of system call
exist in mips architecture. We have to change the value of
__NR_Linux_syscalls, if we add or delete a system call.

One of the patch in this patch series has a script which
will generate a uapi header based on syscall.tbl file.
The syscall.tbl file contains the total number of system
calls information. So we have two option to update __NR-
_Linux_syscalls value.

1. Update __NR_Linux_syscalls in asm/unistd.h manually
   by counting the no.of system calls. No need to update
   __NR_Linux_syscalls until we either add a new system
   call or delete existing system call.

2. We can keep this feature it above mentioned script,
   that will count the number of syscalls and keep it in
   a generated file. In this case we don't need to expli-
   citly update __NR_Linux_syscalls in asm/unistd.h file.

The 2nd option will be the recommended one. For that, I
added the __NR_syscalls macro in uapi/asm/unistd.h along
with __NR_Linux_syscalls. The macro __NR_syscalls also
added for making the name convention same across all
architecture. While __NR_syscalls isn't strictly part of
the uapi, having it as part of the generated header to
simplifies the implementation. We also need to enclose
this macro with #ifdef __KERNEL__ to avoid side effects.
Signed-off-by: default avatarFiroz Khan <firoz.khan@linaro.org>
Signed-off-by: default avatarPaul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: y2038@lists.linaro.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: arnd@arndb.de
Cc: deepa.kernel@gmail.com
Cc: marcin.juszkiewicz@linaro.org
      ef2512c8
  3. 05 Dec, 2018 1 commit
    • Paul Burton's avatar
      MIPS: Expand MIPS32 ASIDs to 64 bits · ff4dd232
      Paul Burton authored 
      ASIDs have always been stored as unsigned longs, ie. 32 bits on MIPS32
kernels. This is problematic because it is feasible for the ASID version
to overflow & wrap around to zero.

We currently attempt to handle this overflow by simply setting the ASID
version to 1, using asid_first_version(), but we make no attempt to
account for the fact that there may be mm_structs with stale ASIDs that
have versions which we now reuse due to the overflow & wrap around.

Encountering this requires that:

  1) A struct mm_struct X is active on CPU A using ASID (V,n).

  2) That mm is not used on CPU A for the length of time that it takes
     for CPU A's asid_cache to overflow & wrap around to the same
     version V that the mm had in step 1. During this time tasks using
     the mm could either be sleeping or only scheduled on other CPUs.

  3) Some other mm Y becomes active on CPU A and is allocated the same
     ASID (V,n).

  4) mm X now becomes active on CPU A again, and now incorrectly has the
     same ASID as mm Y.

Where struct mm_struct ASIDs are represented above in the format
(version, EntryHi.ASID), and on a typical MIPS32 system version will be
24 bits wide & EntryHi.ASID will be 8 bits wide.

The length of time required in step 2 is highly dependent upon the CPU &
workload, but for a hypothetical 2GHz CPU running a workload which
generates a new ASID every 10000 cycles this period is around 248 days.
Due to this long period of time & the fact that tasks need to be
scheduled in just the right (or wrong, depending upon your inclination)
way, this is obviously a difficult bug to encounter but it's entirely
possible as evidenced by reports.

In order to fix this, simply extend ASIDs to 64 bits even on MIPS32
builds. This will extend the period of time required for the
hypothetical system above to encounter the problem from 28 days to
around 3 trillion years, which feels safely outside of the realms of
possibility.

The cost of this is slightly more generated code in some commonly
executed paths, but this is pretty minimal:

                         | Code Size Gain | Percentage
  -----------------------|----------------|-------------
    decstation_defconfig |           +270 | +0.00%
        32r2el_defconfig |           +652 | +0.01%
        32r6el_defconfig |          +1000 | +0.01%

I have been unable to measure any change in performance of the LMbench
lat_ctx or lat_proc tests resulting from the 64b ASIDs on either
32r2el_defconfig+interAptiv or 32r6el_defconfig+I6500 systems.
Signed-off-by: default avatarPaul Burton <paul.burton@mips.com>
Suggested-by: default avatarJames Hogan <jhogan@kernel.org>
References: https://lore.kernel.org/linux-mips/80B78A8B8FEE6145A87579E8435D78C30205D5F3@fzex.ruijie.com.cn/
References: https://lore.kernel.org/linux-mips/1488684260-18867-1-git-send-email-jiwei.sun@windriver.com/
Cc: Jiwei Sun <jiwei.sun@windriver.com>
Cc: Yu Huabing <yhb@ruijie.com.cn>
Cc: stable@vger.kernel.org # 2.6.12+
Cc: linux-mips@vger.kernel.org
      ff4dd232
  5. 04 Dec, 2018 6 commits
  7. 03 Dec, 2018 1 commit
    • Mathieu Malaterre's avatar
      mips: annotate implicit fall throughs · 69095e39
      Mathieu Malaterre authored 
      There is a plan to build the kernel with -Wimplicit-fallthrough and
these places in the code produced warnings. Fix them up.

This patch produces no change in behaviour, but should be reviewed in
case these are actually bugs not intentional fallthoughs.
Signed-off-by: default avatarMathieu Malaterre <malat@debian.org>
Signed-off-by: default avatarPaul Burton <paul.burton@mips.com>
Cc: Kees Cook <keescook@google.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
      69095e39
  9. 27 Nov, 2018 2 commits
  11. 22 Nov, 2018 1 commit
    • Paul Burton's avatar
      MIPS: Only include mmzone.h when CONFIG_NEED_MULTIPLE_NODES=y · 66a4059b
      Paul Burton authored 
      MIPS' asm/mmzone.h includes the machine/platform mmzone.h
unconditionally, but since commit bb53fdf3 ("MIPS: c-r4k: Add
r4k_blast_scache_node for Loongson-3") is included by asm/rk4cache.h for
all r4k-style configs regardless of CONFIG_NEED_MULTIPLE_NODES.

This is problematic when CONFIG_NEED_MULTIPLE_NODES=n because both the
loongson3 & ip27 mmzone.h headers unconditionally define the NODE_DATA
preprocessor macro which is aready defined by linux/mmzone.h, resulting
in the following build error:

  In file included from ./arch/mips/include/asm/mmzone.h:10,
                   from ./arch/mips/include/asm/r4kcache.h:23,
                   from arch/mips/mm/c-r4k.c:33:
  ./arch/mips/include/asm/mach-loongson64/mmzone.h:48: error: "NODE_DATA" redefined [-Werror]
   #define NODE_DATA(n)  (&__node_data[(n)]->pglist)

  In file included from ./include/linux/topology.h:32,
                   from ./include/linux/irq.h:19,
                   from ./include/asm-generic/hardirq.h:13,
                   from ./arch/mips/include/asm/hardirq.h:16,
                   from ./include/linux/hardirq.h:9,
                   from arch/mips/mm/c-r4k.c:11:
  ./include/linux/mmzone.h:907: note: this is the location of the previous definition
   #define NODE_DATA(nid)  (&contig_page_data)

Resolve this by only including the machine mmzone.h when
CONFIG_NEED_MULTIPLE_NODES=y, which also removes the need for the empty
mach-generic version of the header which we delete.
Signed-off-by: default avatarPaul Burton <paul.burton@mips.com>
Fixes: bb53fdf3 ("MIPS: c-r4k: Add r4k_blast_scache_node for Loongson-3")
      66a4059b
  13. 21 Nov, 2018 28 commits
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