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Subject[PATCH v4 0/2] Fix RISC-V's arch-topology reporting
From: Conor Dooley <>

Hey all,
It's my first time messing around with arch/ code at all, let alone
more than one arch, so forgive me if I have screwed up how to do a
migration like this.

The goal here is the fix the incorrectly reported arch topology on
RISC-V which seems to have been broken since it was added.
cpu, package and thread IDs are all currently reported as -1, so tools
like lstopo think systems have multiple threads on the same core when
this is not true:

arm64's topology code basically applies to RISC-V too, so it has been
made generic along with the removal of MPIDR related code, which
appears to be redudant code since '3102bc0e6ac7 ("arm64: topology: Stop
using MPIDR for topology information")' replaced the code that actually
interacted with MPIDR with default values.

I only built tested for arm{,64} , so hopefully it is not broken when
used. Testing on both arm64 & !SMP RISC-V would really be appreciated!

For V2, I dropped the idea of doing a RISC-V specific implementation
followed by a move to the generic code & just went for the more straight
forward method of moving to the shared version first. I also dropped the

V3 moves store_cpu_topology()'s definition down inside the arch check
alongside the init function so that boot on 32bit arm is not broken.

V4 has moved the RISC-V boot hart's call to store_cpu_topology() later
into the boot process it is now right before SMP is brought up (or not
in the case of !SMP). This prevents calling detect_cache_attributes()
while we cannot allocate memory.

V4 is also rebased on next-20220715 to get Sudeep's most recent
arch_topology patchset.


Conor Dooley (2):
arm64: topology: move store_cpu_topology() to shared code
riscv: topology: fix default topology reporting

arch/arm64/kernel/topology.c | 40 ------------------------------------
arch/riscv/Kconfig | 2 +-
arch/riscv/kernel/smpboot.c | 3 ++-
drivers/base/arch_topology.c | 19 +++++++++++++++++
4 files changed, 22 insertions(+), 42 deletions(-)

base-commit: 6014cfa5bf32cf8c5c58b3cfd5ee0e1542c8a825

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