[PATCH v2 1/2] powerpc/powernv: Get L1D flush requirements from device-tree

[Michael Ellerman]

Joel Stanley <joel at jms.id.au> writes:
> On Mon, 4 Apr 2022 at 10:15, Russell Currey <ruscur at 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 <joel at jms.id.au>
>> Signed-off-by: Russell Currey <ruscur at 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/ ?

I suspect some of them might fail, because they have specific knowledge
of things and might need an update.

cheers