linux-kernel - [PATCH 0/2] riscv: Fix race conditions in PR_RISCV_SET_ICACHE_FLUSH

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Message-Id: <20240813-fix_fencei_optimization-v1-0-2aadc2cdde95@rivosinc.com>
Date: Tue, 13 Aug 2024 16:02:16 -0700
From: Charlie Jenkins <charlie@...osinc.com>
To: Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
 Alexandre Ghiti <alexghiti@...osinc.com>, Atish Patra <atishp@...osinc.com>, 
 Samuel Holland <samuel.holland@...ive.com>, 
 Andrea Parri <parri.andrea@...il.com>
Cc: Palmer Dabbelt <palmer@...osinc.com>, linux-riscv@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, Charlie Jenkins <charlie@...osinc.com>
Subject: [PATCH 0/2] riscv: Fix race conditions in
 PR_RISCV_SET_ICACHE_FLUSH_CTX

There are two race conditions possible with
PR_RISCV_SET_ICACHE_FLUSH_CTX. The first one can be seen by enabling
DEBUG_PREEMPT and using this prctl which will warn with BUG: using
smp_processor_id() in preemptible. This can be fixed by disabling
preemption during this prctl handling. Another race condition is present
when the mm->context.icache_stale_mask is changed by a thread while a
different thread in the same mm context is between switch_mm() and
switch_to() during a context switch.

Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
---
Charlie Jenkins (2):
      riscv: Disable preemption while handling PR_RISCV_CTX_SW_FENCEI_OFF
      riscv: Eagerly flush in flush_icache_deferred()

 arch/riscv/include/asm/switch_to.h | 19 ++++++++++++++++---
 arch/riscv/mm/cacheflush.c         | 13 +++++++------
 arch/riscv/mm/context.c            |  6 +-----
 3 files changed, 24 insertions(+), 14 deletions(-)
---
base-commit: 7c626ce4bae1ac14f60076d00eafe71af30450ba
change-id: 20240812-fix_fencei_optimization-3f81ac200505
-- 
- Charlie