Joel Stanley <j...@jms.id.au> writes:
> On Tue, 5 Apr 2022 at 06:13, Michael Ellerman <m...@ellerman.id.au> wrote:
>>
>> Joel Stanley <j...@jms.id.au> writes:
>> > On Mon, 4 Apr 2022 at 10:15, Russell Currey <rus...@russell.cc> wrote:
>> >>
>> >> The device-tree properties no-need-l1d-flush-msr-pr-1-to-0 and
>> >> no-need-l1d-flush-kernel-on-user-access are the equivalents of
>> >> H_CPU_BEHAV_NO_L1D_FLUSH_ENTRY and H_CPU_BEHAV_NO_L1D_FLUSH_UACCESS
>> >> from the H_GET_CPU_CHARACTERISTICS hcall on pseries respectively.
>> >>
>> >> In commit d02fa40d759f ("powerpc/powernv: Remove POWER9 PVR version
>> >> check for entry and uaccess flushes") the condition for disabling the
>> >> L1D flush on kernel entry and user access was changed from any non-P9
>> >> CPU to only checking P7 and P8. Without the appropriate device-tree
>> >> checks for newer processors on powernv, these flushes are unnecessarily
>> >> enabled on those systems. This patch corrects this.
>> >>
>> >> Fixes: d02fa40d759f ("powerpc/powernv: Remove POWER9 PVR version check
>> >> for entry and uaccess flushes")
>> >> Reported-by: Joel Stanley <j...@jms.id.au>
>> >> Signed-off-by: Russell Currey <rus...@russell.cc>
>> >
>> > I booted both patches in this series on a power10 powernv machine,
>> > applied on top of v5.18-rc1:
>> >
>> > $ dmesg |grep -i flush
>> > [ 0.000000] rfi-flush: fallback displacement flush available
>> > [ 0.000000] rfi-flush: patched 12 locations (no flush)
>> > [ 0.000000] count-cache-flush: flush disabled.
>> > [ 0.000000] link-stack-flush: flush disabled.
>> >
>> > $ grep . /sys/devices/system/cpu/vulnerabilities/*
>> > /sys/devices/system/cpu/vulnerabilities/itlb_multihit:Not affected
>> > /sys/devices/system/cpu/vulnerabilities/l1tf:Not affected
>> > /sys/devices/system/cpu/vulnerabilities/mds:Not affected
>> > /sys/devices/system/cpu/vulnerabilities/meltdown:Not affected
>> > /sys/devices/system/cpu/vulnerabilities/spec_store_bypass:Not affected
>> > /sys/devices/system/cpu/vulnerabilities/spectre_v1:Mitigation: __user
>> > pointer sanitization, ori31 speculation barrier enabled
>> > /sys/devices/system/cpu/vulnerabilities/spectre_v2:Mitigation:
>> > Software count cache flush (hardware accelerated), Software link stack
>> > flush
>> > /sys/devices/system/cpu/vulnerabilities/srbds:Not affected
>> > /sys/devices/system/cpu/vulnerabilities/tsx_async_abort:Not affected
>> >
>> > Does that match what we expect?
>>
>> AFAIK yes. Happy for ruscur to correct me though.
>>
>> Can you also try running the kernel selftests under
>> tools/testing/selftests/powerpc/security/ ?
>
> Here's the results when booted with no_spectrev2 (which I keep on
> doing by accident, as this machine has it in it's nvram):
>
> make[1]: Entering directory
> '/home/joel/dev/kernels/linus/tools/testing/selftests/powerpc/security'
> TAP version 13
> 1..5
> # selftests: powerpc/security: rfi_flush
> # test: rfi_flush_test
> # tags: git_version:v5.18-rc1-0-g312310928417
> # PASS (L1D misses with rfi_flush=0: 63101900 < 95000000) [10/10 pass]
> # PASS (L1D misses with rfi_flush=1: 196001003 > 190000000) [10/10 pass]
> # success: rfi_flush_test
> ok 1 selftests: powerpc/security: rfi_flush
> # selftests: powerpc/security: entry_flush
> # test: entry_flush_test
> # tags: git_version:v5.18-rc1-0-g312310928417
> # PASS (L1D misses with entry_flush=0: 52766044 < 95000000) [10/10 pass]
> # PASS (L1D misses with entry_flush=1: 196082833 > 190000000) [10/10 pass]
> # success: entry_flush_test
> ok 2 selftests: powerpc/security: entry_flush
> # selftests: powerpc/security: uaccess_flush
> # test: uaccess_flush_test
> # tags: git_version:v5.18-rc1-0-g312310928417
> # PASS (L1D misses with uaccess_flush=0: 68646267 < 95000000) [10/10 pass]
> # PASS (L1D misses with uaccess_flush=1: 194177355 > 190000000) [10/10 pass]
> # success: uaccess_flush_test
> ok 3 selftests: powerpc/security: uaccess_flush
> # selftests: powerpc/security: spectre_v2
> # test: spectre_v2
> # tags: git_version:v5.18-rc1-0-g312310928417
> # sysfs reports: 'Vulnerable'
> # PM_BR_PRED_CCACHE: result 0 running/enabled 2090650862
> # PM_BR_MPRED_CCACHE: result 1 running/enabled 2090648016
> # Miss percent 0 %
> # OK - Measured branch prediction rates match reported spectre v2 mitigation.
> # success: spectre_v2
> ok 4 selftests: powerpc/security: spectre_v2
> # selftests: powerpc/security: mitigation-patching.sh
> # Spawned threads enabling/disabling mitigations ...
> # Waiting for timeout ...
> # OK
> ok 5 selftests: powerpc/security: mitigation-patching.sh
>
>
> Here's the same thing without the command line option set:
Thanks.
> # test: spectre_v2
> # tags: git_version:v5.18-rc1-0-g312310928417
> # sysfs reports: 'Mitigation: Software count cache flush (hardware
> accelerated), Software link stack flush'
> # PM_BR_PRED_CCACHE: result 0 running/enabled 2016985490
> # PM_BR_MPRED_CCACHE: result 1 running/enabled 2016981520
> # Miss percent 0 %
> # OK - Measured branch prediction rates match reported spectre v2 mitigation.
> # success: spectre_v2
This passed, but looks wrong, it says there were zero branches correctly
predicted.
I think the PMU events were are using are wrong for P10, the test will
need updating to use the right events for P10.
cheers
