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Date: Wed, 23 Jan 2019 11:04:16 +0100
From: Christophe Leroy <christophe.leroy@....fr>
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>,
Nicholas Piggin <npiggin@...il.com>
Cc: Mike Rapoport <rppt@...ux.ibm.com>, linuxppc-dev@...ts.ozlabs.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v13 00/10] powerpc: Switch to CONFIG_THREAD_INFO_IN_TASK
Le 12/01/2019 à 10:55, Christophe Leroy a écrit :
> The purpose of this serie is to activate CONFIG_THREAD_INFO_IN_TASK which
> moves the thread_info into task_struct.
>
> Moving thread_info into task_struct has the following advantages:
> - It protects thread_info from corruption in the case of stack
> overflows.
> - Its address is harder to determine if stack addresses are
> leaked, making a number of attacks more difficult.
I ran null_syscall and context_switch benchmark selftests and the result
is surprising. There is slight degradation in context_switch and a
significant one on null_syscall:
Without the serie:
~# chrt -f 98 ./context_switch --no-altivec --no-vector --no-fp
55542
55562
55564
55562
55568
...
~# ./null_syscall
2546.71 ns 336.17 cycles
With the serie:
~# chrt -f 98 ./context_switch --no-altivec --no-vector --no-fp
55138
55142
55152
55144
55142
~# ./null_syscall
3479.54 ns 459.30 cycles
So 0,8% less context switches per second and 37% more time for one syscall ?
Any idea ?
Christophe
>
> Changes since v12:
> - Patch 1: Taken comment from Mike (re-introduced the 'panic' in case memblock allocation fails in setup_64.c
> - Patch 1: Added alloc_stack() function in setup_32.c to also panic in case of allocation failure.
>
> Changes since v11:
> - Rebased on 81775f5563fa ("Automatic merge of branches 'master', 'next' and 'fixes' into merge")
> - Added a first patch to change memblock allocs to functions returning virtual addrs. This removes
> the memset() which were the only remaining stuff in irq_ctx_init() and exc_lvl_ctx_init() at the end.
> - dropping irq_ctx_init() and exc_lvl_ctx_init() in patch 5 (powerpc: Activate CONFIG_THREAD_INFO_IN_TASK)
> - A few cosmetic changes in commit log and code.
>
> Changes since v10:
> - Rebased on 21622a0d2023 ("Automatic merge of branches 'master', 'next' and 'fixes' into merge")
> ==> Fixed conflict in setup_32.S
>
> Changes since v9:
> - Rebased on 183cbf93be88 ("Automatic merge of branches 'master', 'next' and 'fixes' into merge")
> ==> Fixed conflict on xmon
>
> Changes since v8:
> - Rebased on e589b79e40d9 ("Automatic merge of branches 'master', 'next' and 'fixes' into merge")
> ==> Main impact was conflicts due to commit 9a8dd708d547 ("memblock: rename memblock_alloc{_nid,_try_nid} to memblock_phys_alloc*")
>
> Changes since v7:
> - Rebased on fb6c6ce7907d ("Automatic merge of branches 'master', 'next' and 'fixes' into merge")
>
> Changes since v6:
> - Fixed validate_sp() to exclude NULL sp in 'regain entire stack space' patch (early crash with CONFIG_KMEMLEAK)
>
> Changes since v5:
> - Fixed livepatch_sp setup by using end_of_stack() instead of hardcoding
> - Fixed PPC_BPF_LOAD_CPU() macro
>
> Changes since v4:
> - Fixed a build failure on 32bits SMP when include/generated/asm-offsets.h is not
> already existing, was due to spaces instead of a tab in the Makefile
>
> Changes since RFC v3: (based on Nick's review)
> - Renamed task_size.h to task_size_user64.h to better relate to what it contains.
> - Handling of the isolation of thread_info cpu field inside CONFIG_SMP #ifdefs moved to a separate patch.
> - Removed CURRENT_THREAD_INFO macro completely.
> - Added a guard in asm/smp.h to avoid build failure before _TASK_CPU is defined.
> - Added a patch at the end to rename 'tp' pointers to 'sp' pointers
> - Renamed 'tp' into 'sp' pointers in preparation patch when relevant
> - Fixed a few commit logs
> - Fixed checkpatch report.
>
> Changes since RFC v2:
> - Removed the modification of names in asm-offsets
> - Created a rule in arch/powerpc/Makefile to append the offset of current->cpu in CFLAGS
> - Modified asm/smp.h to use the offset set in CFLAGS
> - Squashed the renaming of THREAD_INFO to TASK_STACK in the preparation patch
> - Moved the modification of current_pt_regs in the patch activating CONFIG_THREAD_INFO_IN_TASK
>
> Changes since RFC v1:
> - Removed the first patch which was modifying header inclusion order in timer
> - Modified some names in asm-offsets to avoid conflicts when including asm-offsets in C files
> - Modified asm/smp.h to avoid having to include linux/sched.h (using asm-offsets instead)
> - Moved some changes from the activation patch to the preparation patch.
>
> Christophe Leroy (10):
> powerpc/irq: use memblock functions returning virtual address
> book3s/64: avoid circular header inclusion in mmu-hash.h
> powerpc: Only use task_struct 'cpu' field on SMP
> powerpc: Prepare for moving thread_info into task_struct
> powerpc: Activate CONFIG_THREAD_INFO_IN_TASK
> powerpc: regain entire stack space
> powerpc: 'current_set' is now a table of task_struct pointers
> powerpc/32: Remove CURRENT_THREAD_INFO and rename TI_CPU
> powerpc/64: Remove CURRENT_THREAD_INFO
> powerpc: clean stack pointers naming
>
> arch/powerpc/Kconfig | 1 +
> arch/powerpc/Makefile | 7 ++
> arch/powerpc/include/asm/asm-prototypes.h | 4 +-
> arch/powerpc/include/asm/book3s/64/mmu-hash.h | 2 +-
> arch/powerpc/include/asm/exception-64s.h | 4 +-
> arch/powerpc/include/asm/irq.h | 18 ++--
> arch/powerpc/include/asm/livepatch.h | 6 +-
> arch/powerpc/include/asm/processor.h | 39 +--------
> arch/powerpc/include/asm/ptrace.h | 2 +-
> arch/powerpc/include/asm/reg.h | 2 +-
> arch/powerpc/include/asm/smp.h | 17 +++-
> arch/powerpc/include/asm/task_size_user64.h | 42 +++++++++
> arch/powerpc/include/asm/thread_info.h | 19 -----
> arch/powerpc/kernel/asm-offsets.c | 10 ++-
> arch/powerpc/kernel/entry_32.S | 66 +++++---------
> arch/powerpc/kernel/entry_64.S | 12 +--
> arch/powerpc/kernel/epapr_hcalls.S | 5 +-
> arch/powerpc/kernel/exceptions-64e.S | 13 +--
> arch/powerpc/kernel/exceptions-64s.S | 2 +-
> arch/powerpc/kernel/head_32.S | 14 +--
> arch/powerpc/kernel/head_40x.S | 4 +-
> arch/powerpc/kernel/head_44x.S | 8 +-
> arch/powerpc/kernel/head_64.S | 1 +
> arch/powerpc/kernel/head_8xx.S | 2 +-
> arch/powerpc/kernel/head_booke.h | 12 +--
> arch/powerpc/kernel/head_fsl_booke.S | 16 ++--
> arch/powerpc/kernel/idle_6xx.S | 8 +-
> arch/powerpc/kernel/idle_book3e.S | 2 +-
> arch/powerpc/kernel/idle_e500.S | 8 +-
> arch/powerpc/kernel/idle_power4.S | 2 +-
> arch/powerpc/kernel/irq.c | 114 +++----------------------
> arch/powerpc/kernel/kgdb.c | 28 ------
> arch/powerpc/kernel/machine_kexec_64.c | 6 +-
> arch/powerpc/kernel/misc_32.S | 17 ++--
> arch/powerpc/kernel/process.c | 40 ++++-----
> arch/powerpc/kernel/setup-common.c | 2 +-
> arch/powerpc/kernel/setup_32.c | 25 +++---
> arch/powerpc/kernel/setup_64.c | 51 +++--------
> arch/powerpc/kernel/smp.c | 16 ++--
> arch/powerpc/kernel/trace/ftrace_64_mprofile.S | 6 +-
> arch/powerpc/kvm/book3s_hv_hmi.c | 1 +
> arch/powerpc/mm/hash_low_32.S | 14 ++-
> arch/powerpc/net/bpf_jit32.h | 5 +-
> arch/powerpc/sysdev/6xx-suspend.S | 5 +-
> arch/powerpc/xmon/xmon.c | 2 +-
> 45 files changed, 249 insertions(+), 431 deletions(-)
> create mode 100644 arch/powerpc/include/asm/task_size_user64.h
>
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