UbiquitousOS
/
OpenCloudOS-Kernel
mirror of https://gitee.com/OpenCloudOS/OpenCloudOS-Kernel.git
11
0
Fork 0
Code Issues Projects Releases Wiki Activity

x86/fpu: Add a helper to prepare AMX state for low-power CPU idle 

When a CPU enters an idle state, a non-initialized AMX register state may
be the cause of preventing a deeper low-power state. Other extended
register states whether initialized or not do not impact the CPU idle
state.

The new helper can ensure the AMX state is initialized before the CPU is
idle, and it will be used by the intel idle driver.

Check the AMX_TILE feature bit before using XGETBV1 as a chain of
dependencies was established via cpuid_deps[]: AMX->XFD->XGETBV1.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20220608164748.11864-2-chang.seok.bae@intel.com
This commit is contained in:
Chang S. Bae 2022-06-08 09:47:47 -07:00 committed by Borislav Petkov
parent ff6992735a
commit f17b168734
3 changed files with 25 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/include/asm/fpu/api.h
View File

@ -164,4 +164,6 @@ static inline bool fpstate_is_confidential(struct fpu_guest *gfpu)
/* prctl */
extern long fpu_xstate_prctl(int option, unsigned long arg2);
extern void fpu_idle_fpregs(void);
#endif /* _ASM_X86_FPU_API_H */

9
arch/x86/include/asm/special_insns.h
View File

@ -295,6 +295,15 @@ 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 */

14
arch/x86/kernel/fpu/core.c
View File

@ -851,3 +851,17 @@ 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)
{
/* Note: AMX_TILE being enabled implies XGETBV1 support */
if (cpu_feature_enabled(X86_FEATURE_AMX_TILE) &&
(xfeatures_in_use() & XFEATURE_MASK_XTILE)) {
tile_release();
fpregs_deactivate(&current->thread.fpu);
}
}