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Backport subject : 内核支持未对齐内存访问 #199

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@uestc-gr uestc-gr commented Jan 21, 2026 •
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issue: #193

目前已backport L0社区系列补丁
https://lore.kernel.org/all/20231004151405.521596-1-cleger@rivosinc.com/
后续的内存对齐其它补丁下次PR提交

测试方法：
1、使用开源最新的opensbi
2、使用新的qemu
https://github.com/rivosinc/qemu/tree/dev/cleger/misaligned
3、启动tcg虚拟机
$ qemu-system-riscv64
-cpu rv64,trap-misaligned-access=true,v=true
-M virt
-m 1024M
-bios fw_dynamic.bin
-kernel Image
4、内核接管非对齐异常处理，临时添加内核测试代码（由于本PR与issues: 202代码有依赖，先提交前半部，这块处理在后面再提PR合入）
test.patch
5、运行测试用例
https://github.com/clementleger/unaligned_test

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github-actions bot commented Jan 21, 2026 •
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开始测试 log: https://github.com/RVCK-Project/rvck/actions/runs/21200083759

参数解析结果
args value
repository RVCK-Project/rvck
head ref pull/199/head
base ref rvck-6.6
LAVA repo RVCK-Project/lavaci
LAVA Template lava-job-template/qemu/qemu-ltp.yaml
Testcase path lava-testcases/common-test/ltp/ltp.yaml
need run job kunit-test,kernel-build,check-patch,lava-trigger

测试完成

详细结果:

RVCK result

check result
kunit-test success
kernel-build success
lava-trigger success
check-patch failure

Kunit Test Result

[06:53:43] Testing complete. Ran 455 tests: passed: 443, skipped: 12

Kernel Build Result

Kernel build succeeded: RVCK-Project/rvck/199/

b07c32ab664b80ebdb7b2d62e5692929 /srv/guix_result/dc1d184b6b147a64a775bcc49cd29d698eedc327/Image
ea8379e428524003011a3f4c499a6da2 /root/initramfs.img

LAVA Check

args:

result:

Lava check done! lava log: https://lava.oerv.ac.cn/scheduler/job/1121

lava result count: [fail]: 173, [pass]: 1435, [skip]: 291

Check Patch Result
Total Errors 1
Total Warnings 9

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github-actions bot commented Jan 27, 2026 •
edited
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开始测试 log: https://github.com/RVCK-Project/rvck/actions/runs/21389419343

参数解析结果
args value
repository RVCK-Project/rvck
head ref pull/199/head
base ref rvck-6.6
LAVA repo RVCK-Project/lavaci
LAVA Template lava-job-template/qemu/qemu-ltp.yaml
Testcase path lava-testcases/common-test/ltp/ltp.yaml
need run job kunit-test,kernel-build,check-patch,lava-trigger

测试完成

详细结果:

RVCK result

check result
kunit-test success
kernel-build success
lava-trigger success
check-patch failure

Kunit Test Result

[08:13:46] Testing complete. Ran 455 tests: passed: 443, skipped: 12

Kernel Build Result

Kernel build succeeded: RVCK-Project/rvck/199/

0227f0e93954e63572bf14edb943f39e /srv/guix_result/e8b9ef1b3f08b0472278fe6b3443f2409926bceb/Image
4b6e057fc295833e18ad3ef2aef1e531 /root/initramfs.img

LAVA Check

args:

result:

Lava check done! lava log: https://lava.oerv.ac.cn/scheduler/job/1167

lava result count: [fail]: 175, [pass]: 1433, [skip]: 291

Check Patch Result
Total Errors 1
Total Warnings 11

@uestc-gr uestc-gr changed the title Backport subject : 支持 SBI FWFT扩展未对齐内存访问异常的委托处理 （暂未完成） Backport subject : 内核支持未对齐内存访问 Jan 27, 2026
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uestc-gr commented Jan 28, 2026

该PR已经完成，请老师评审，由于本PR与issues: 202代码有依赖且整体补丁较多，分两次提交，本次先提交前部分代码

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fangyu0809 commented Jan 30, 2026 •
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后面https://github.com/RVCK-Project/rvck/pull/207，依赖当前这个pr，帮忙尽快评审
@sterling-teng

@sterling-teng
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sterling-teng commented Feb 1, 2026

后面https://github.com/RVCK-Project/rvck/pull/207，依赖当前这个pr，帮忙尽快评审 @sterling-teng

好的，月末月初在rebase滚动分支，rebase后审阅。

clementleger and others added 8 commits February 2, 2026 23:24
@clementleger @uestc-gr
riscv: add support for misaligned trap handling in S-mode
f9d2586 
mainline inclusion
from mainline-6.7-rc1
commit 7c83232
category: feature
bugzilla: RVCK-Project#193

--------------------------------

Misalignment trap handling is only supported for M-mode and uses direct
accesses to user memory. In S-mode, when handling usermode fault, this
requires to use the get_user()/put_user() accessors. Implement
load_u8(), store_u8() and get_insn() using these accessors for
userspace and direct text access for kernel.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20231004151405.521596-3-cleger@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Gao Rui <gao.rui@zte.com.cn>
@clementleger @uestc-gr
riscv: report perf event for misaligned fault
0388e10 
mainline inclusion
from mainline-6.7-rc1
commit 89c12fe
category: feature
bugzilla: RVCK-Project#193

--------------------------------

Add missing calls to account for misaligned fault event using
perf_sw_event().

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20231004151405.521596-4-cleger@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Gao Rui <gao.rui@zte.com.cn>
@clementleger @uestc-gr
riscv: add floating point insn support to misaligned access emulation
5cd9d23 
mainline inclusion
from mainline-6.7-rc1
commit 7c586a5
category: feature
bugzilla: RVCK-Project#193

--------------------------------

This support is partially based of openSBI misaligned emulation floating
point instruction support. It provides support for the existing
floating point instructions (both for 32/64 bits as well as compressed
ones). Since floating point registers are not part of the pt_regs
struct, we need to modify them directly using some assembly. We also
dirty the pt_regs status in case we modify them to be sure context
switch will save FP state. With this support, Linux is on par with
openSBI support.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Link: https://lore.kernel.org/r/20231004151405.521596-5-cleger@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Gao Rui <gao.rui@zte.com.cn>
@clementleger @uestc-gr
riscv: add support for sysctl unaligned_enabled control
18e6960 
mainline inclusion
from mainline-6.7-rc1
commit bc38f61
category: feature
bugzilla: RVCK-Project#193

--------------------------------

This sysctl tuning option allows the user to disable misaligned access
handling globally on the system. This will also be used by misaligned
detection code to temporarily disable misaligned access handling.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20231004151405.521596-6-cleger@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Gao Rui <gao.rui@zte.com.cn>
@clementleger @uestc-gr
riscv: report misaligned accesses emulation to hwprobe
045b1d6 
mainline inclusion
from mainline-6.7-rc1
commit 71c54b3
category: feature
bugzilla: RVCK-Project#193

--------------------------------

hwprobe provides a way to report if misaligned access are emulated. In
order to correctly populate that feature, we can check if it actually
traps when doing a misaligned access. This can be checked using an
exception table entry which will actually be used when a misaligned
access is done from kernel mode.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Link: https://lore.kernel.org/r/20231004151405.521596-8-cleger@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Gao Rui <gao.rui@zte.com.cn>
@clementleger @uestc-gr
riscv: add support for PR_SET_UNALIGN and PR_GET_UNALIGN
e80d21e 
mainline inclusion
from mainline-6.7-rc1
commit 9f23a5d
category: feature
bugzilla: RVCK-Project#193

--------------------------------

Now that trap support is ready to handle misalignment errors in S-mode,
allow the user to control the behavior of misaligned accesses using
prctl(PR_SET_UNALIGN). Add an align_ctl flag in thread_struct which
will be used to determine if we should SIGBUS the process or not on
such fault.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20231004151405.521596-9-cleger@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Gao Rui <gao.rui@zte.com.cn>
@evangreen @uestc-gr
RISC-V: Remove __init on unaligned_emulation_finish()
cfdd25f 
mainline inclusion
from mainline-6.7-rc1
commit 6eb7a64
category: feature
bugzilla: RVCK-Project#193

--------------------------------

This function shouldn't be __init, since it's called during hotplug. The
warning says it well enough:

WARNING: modpost: vmlinux: section mismatch in reference:
check_unaligned_access_all_cpus+0x13a (section: .text) ->
unaligned_emulation_finish (section: .init.text)

Signed-off-by: Evan Green <evan@rivosinc.com>
Fixes: 71c54b3 ("riscv: report misaligned accesses emulation to hwprobe")
Link: https://lore.kernel.org/r/20231106231105.3141413-1-evan@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Gao Rui <gao.rui@zte.com.cn>
@evangreen @uestc-gr
RISC-V: Probe misaligned access speed in parallel
f51b268 
mainline inclusion
from mainline-6.7-rc1
commit 55e0bf4
category: feature
bugzilla: RVCK-Project#193

--------------------------------

Probing for misaligned access speed takes about 0.06 seconds. On a
system with 64 cores, doing this in smp_callin() means it's done
serially, extending boot time by 3.8 seconds. That's a lot of boot time.

Instead of measuring each CPU serially, let's do the measurements on
all CPUs in parallel. If we disable preemption on all CPUs, the
jiffies stop ticking, so we can do this in stages of 1) everybody
except core 0, then 2) core 0. The allocations are all done outside of
on_each_cpu() to avoid calling alloc_pages() with interrupts disabled.

For hotplugged CPUs that come in after the boot time measurement,
register CPU hotplug callbacks, and do the measurement there. Interrupts
are enabled in those callbacks, so they're fine to do alloc_pages() in.

Reported-by: Jisheng Zhang <jszhang@kernel.org>
Closes: https://lore.kernel.org/all/mhng-9359993d-6872-4134-83ce-c97debe1cf9a@palmer-ri-x1c9/T/#mae9b8f40016f9df428829d33360144dc5026bcbf
Fixes: 584ea65 ("RISC-V: Probe for unaligned access speed")
Signed-off-by: Evan Green <evan@rivosinc.com>
Link: https://lore.kernel.org/r/20231106225855.3121724-1-evan@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Gao Rui <gao.rui@zte.com.cn>
@github-actions
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github-actions bot commented Feb 2, 2026

开始测试 log: https://github.com/RVCK-Project/rvck/actions/runs/21596061406

参数解析结果
args value
repository RVCK-Project/rvck
head ref pull/199/head
base ref rvck-6.6
LAVA repo RVCK-Project/lavaci
LAVA Template lava-job-template/qemu/qemu-ltp.yaml
Testcase path lava-testcases/common-test/ltp/ltp.yaml
need run job kunit-test,kernel-build,check-patch,lava-trigger

@uestc-gr
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uestc-gr commented Feb 2, 2026

后面https://github.com/RVCK-Project/rvck/pull/207，依赖当前这个pr，帮忙尽快评审 @sterling-teng

好的，月末月初在rebase滚动分支，rebase后审阅。

已经rebase了请老师继续评审， @sterling-teng CC: @fangyu0809

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5 participants

@uestc-gr @fangyu0809 @sterling-teng @clementleger @evangreen