From: Mark Rutland <mark.rutland@arm.com> mainline inclusion from mainline-v6.16-rc1 commit 6ef1d778ce56c5bde1ac0a1f85fd9710efde6724 category: feature bugzilla: https://atomgit.com/openeuler/kernel/issues/8904 CVE: NA Reference: https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commi... ---------------------------------------------------------------------- In a few places we want to transition a task from streaming mode to non-streaming mode, e.g. signal delivery where we historically tried to use an SMSTOP SM instruction. Add a new helper to manipulate a task's state in the same way as an SMSTOP SM instruction. I have not added a corresponding helper to simulate the effects of SMSTART SM. Only ptrace transitions a task into streaming mode, and ptrace has distinct semantics for such transitions. Per ARM DDI 0487 L.a, section B1.4.6: | RRSWFQ | When the Effective value of PSTATE.SM is changed by any method from 0 | to 1, an entry to Streaming SVE mode is performed, and all implemented | bits of Streaming SVE register state are set to zero. | RKFRQZ | When the Effective value of PSTATE.SM is changed by any method from 1 | to 0, an exit from Streaming SVE mode is performed, and in the | newly-entered mode, all implemented bits of the SVE scalable vector | registers, SVE predicate registers, and FFR, are set to zero. Per ARM DDI 0487 L.a, section C5.2.9: | On entry to or exit from Streaming SVE mode, FPMR is set to 0 Per ARM DDI 0487 L.a, section C5.2.10: | On entry to or exit from Streaming SVE mode, FPSR.{IOC, DZC, OFC, UFC, | IXC, IDC, QC} are set to 1 and the remaining bits are set to 0. This means bits 0, 1, 2, 3, 4, 7, and 27 respectively, i.e. 0x0800009f Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Mark Brown <broonie@kernel.org> Cc: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20250508132644.1395904-9-mark.rutland@arm.com Signed-off-by: Will Deacon <will@kernel.org> Signed-off-by: Qinxin Xia <xiaqinxin@huawei.com> Signed-off-by: Hongye Lin <linhongye@h-partners.com> --- arch/arm64/include/asm/fpsimd.h | 2 ++ arch/arm64/kernel/fpsimd.c | 22 ++++++++++++++++++++++ 2 files changed, 24 insertions(+) diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h index 18e06469a932..75e0086d0202 100644 --- a/arch/arm64/include/asm/fpsimd.h +++ b/arch/arm64/include/asm/fpsimd.h @@ -88,6 +88,8 @@ static inline bool thread_za_enabled(struct thread_struct *thread) return system_supports_sme() && (thread->svcr & SVCR_ZA_MASK); } +extern void task_smstop_sm(struct task_struct *task); + /* Maximum VL that SVE/SME VL-agnostic software can transparently support */ #define VL_ARCH_MAX 0x100 diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index a8f78d565e37..a81103cdcbdb 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -728,6 +728,28 @@ static inline void sve_to_fpsimd(struct task_struct *task) } } +static inline void __fpsimd_zero_vregs(struct user_fpsimd_state *fpsimd) +{ + memset(&fpsimd->vregs, 0, sizeof(fpsimd->vregs)); +} + +/* + * Simulate the effects of an SMSTOP SM instruction. + */ +void task_smstop_sm(struct task_struct *task) +{ + if (!thread_sm_enabled(&task->thread)) + return; + + __fpsimd_zero_vregs(&task->thread.uw.fpsimd_state); + task->thread.uw.fpsimd_state.fpsr = 0x0800009f; + if (system_supports_fpmr()) + task->thread.fpmr = 0; + + task->thread.svcr &= ~SVCR_SM_MASK; + task->thread.fp_type = FP_STATE_FPSIMD; +} + void cpu_enable_fpmr(const struct arm64_cpu_capabilities *__always_unused p) { write_sysreg_s(read_sysreg_s(SYS_SCTLR_EL1) | SCTLR_EL1_EnFPM_MASK, -- 2.33.0