Messages in this thread Patch in this message | | | From | "Chang S. Bae" <> | Subject | [PATCH v3 2/3] x86/fpu: Add a helper to prepare AMX state for low-power CPU idle | Date | Thu, 24 Mar 2022 19:22:18 -0700 |
| |
When a CPU enters an idle state, non-initialized states left in large registers may be the cause of preventing deeper low-power states.
The new helper ensures the AMX state is initialized to make the CPU ready for low-power states. It will be used by the intel idle driver.
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- Changes from v2: * Check the feature flag instead of fpu_state_size_dynamic() (Dave Hansen).
Changes from v1: * Check the dynamic state flag first, to avoid #UD with XGETBV(1). --- arch/x86/include/asm/fpu/api.h | 2 ++ arch/x86/include/asm/special_insns.h | 9 +++++++++ arch/x86/kernel/fpu/core.c | 13 +++++++++++++ 3 files changed, 24 insertions(+)
diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h index c83b3020350a..df48912fd1c8 100644 --- a/arch/x86/include/asm/fpu/api.h +++ b/arch/x86/include/asm/fpu/api.h @@ -165,4 +165,6 @@ static inline bool fpstate_is_confidential(struct fpu_guest *gfpu) struct task_struct; extern long fpu_xstate_prctl(struct task_struct *tsk, int option, unsigned long arg2); +extern void fpu_idle_fpregs(void); + #endif /* _ASM_X86_FPU_API_H */ diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h index 68c257a3de0d..d434fbaeb3ff 100644 --- a/arch/x86/include/asm/special_insns.h +++ b/arch/x86/include/asm/special_insns.h @@ -294,6 +294,15 @@ static inline int enqcmds(void __iomem *dst, const void *src) return 0; } +static inline void tile_release(void) +{ + /* + * Instruction opcode for TILERELEASE; supported in binutils + * version >= 2.36. + */ + asm volatile(".byte 0xc4, 0xe2, 0x78, 0x49, 0xc0"); +} + #endif /* __KERNEL__ */ #endif /* _ASM_X86_SPECIAL_INSNS_H */ diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 8dea01ffc5c1..3507609e22d7 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -847,3 +847,16 @@ int fpu__exception_code(struct fpu *fpu, int trap_nr) */ return 0; } + +/* + * Initialize register state that may prevent from entering low-power idle. + * This function will be invoked from the cpuidle driver only when needed. + */ +void fpu_idle_fpregs(void) +{ + if (cpu_feature_enabled(X86_FEATURE_XGETBV1) && + (xfeatures_in_use() & XFEATURE_MASK_XTILE)) { + tile_release(); + fpregs_deactivate(¤t->thread.fpu); + } +} -- 2.17.1
| |