From: Mark Brown broonie@kernel.org
commit 2f43f549cd0b3164ea0345e59aa3958c0d243383 upstream.
When the value of ZT is set via ptrace we don't disable traps for SME. This means that when a the task has never used SME before then the value set via ptrace will never be seen by the target task since it will trigger a SME access trap which will flush the register state.
Disable SME traps when setting ZT, this means we also need to allocate storage for SVE if it is not already allocated, for the benefit of streaming SVE.
Fixes: f90b529bcbe5 ("arm64/sme: Implement ZT0 ptrace support") Signed-off-by: Mark Brown broonie@kernel.org Cc: stable@vger.kernel.org # 6.3.x Link: https://lore.kernel.org/r/20230816-arm64-zt-ptrace-first-use-v2-1-00aa82847e... Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/kernel/ptrace.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index a31af7a1abe3..187aa2b175b4 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -1177,6 +1177,11 @@ static int zt_set(struct task_struct *target, if (!system_supports_sme2()) return -EINVAL;
+ /* Ensure SVE storage in case this is first use of SME */ + sve_alloc(target, false); + if (!target->thread.sve_state) + return -ENOMEM; + if (!thread_za_enabled(&target->thread)) { sme_alloc(target, true); if (!target->thread.sme_state) @@ -1186,8 +1191,10 @@ static int zt_set(struct task_struct *target, ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, thread_zt_state(&target->thread), 0, ZT_SIG_REG_BYTES); - if (ret == 0) + if (ret == 0) { target->thread.svcr |= SVCR_ZA_MASK; + set_tsk_thread_flag(target, TIF_SME); + }
fpsimd_flush_task_state(target);