Messages in this thread Patch in this message | | | From | "Chang S. Bae" <> | Subject | [RESEND PATCH v6 07/12] x86/fsgsbase/64: Introduce the FIND_PERCPU_BASE macro | Date | Fri, 15 Mar 2019 13:06:40 -0700 |
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GSBASE is used to find per-CPU data in the kernel. But when it is unknown, the per-CPU base can be found from the per_cpu_offset table with a CPU NR. The CPU NR is extracted from the limit field of the CPUNODE entry in GDT, or by the RDPID instruction.
Also, add the GAS-compatible RDPID macro.
The new macro will be used on a following patch.
Suggested-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Andi Kleen <ak@linux.intel.com> --- arch/x86/include/asm/fsgsbase.h | 41 +++++++++++++++++++++++++++++++++ arch/x86/include/asm/inst.h | 15 ++++++++++++ 2 files changed, 56 insertions(+)
diff --git a/arch/x86/include/asm/fsgsbase.h b/arch/x86/include/asm/fsgsbase.h index aefd53767a5d..5e3dfbe8c1bf 100644 --- a/arch/x86/include/asm/fsgsbase.h +++ b/arch/x86/include/asm/fsgsbase.h @@ -78,6 +78,47 @@ extern void x86_gsbase_write_cpu_inactive(unsigned long gsbase); #endif /* CONFIG_X86_64 */ +#else /* __ASSEMBLY__ */ + +#ifdef CONFIG_X86_64 + +#include <asm/inst.h> + +#ifdef CONFIG_SMP + +/* + * CPU/node NR is loaded from the limit (size) field of a special segment + * descriptor entry in GDT. + */ +.macro LOAD_CPU_AND_NODE_SEG_LIMIT reg:req + movq $__CPUNODE_SEG, \reg + lsl \reg, \reg +.endm + +/* + * Fetch the per-CPU GSBASE value for this processor and put it in @reg. + * We normally use %gs for accessing per-CPU data, but we are setting up + * %gs here and obviously can not use %gs itself to access per-CPU data. + */ +.macro FIND_PERCPU_BASE reg:req + ALTERNATIVE \ + "LOAD_CPU_AND_NODE_SEG_LIMIT \reg", \ + "RDPID \reg", \ + X86_FEATURE_RDPID + andq $VDSO_CPUNODE_MASK, \reg + movq __per_cpu_offset(, \reg, 8), \reg +.endm + +#else + +.macro FIND_PERCPU_BASE reg:req + movq pcpu_unit_offsets(%rip), \reg +.endm + +#endif /* CONFIG_SMP */ + +#endif /* CONFIG_X86_64 */ + #endif /* __ASSEMBLY__ */ #endif /* _ASM_FSGSBASE_H */ diff --git a/arch/x86/include/asm/inst.h b/arch/x86/include/asm/inst.h index f5a796da07f8..d063841a17e3 100644 --- a/arch/x86/include/asm/inst.h +++ b/arch/x86/include/asm/inst.h @@ -306,6 +306,21 @@ .endif MODRM 0xc0 movq_r64_xmm_opd1 movq_r64_xmm_opd2 .endm + +.macro RDPID opd + REG_TYPE rdpid_opd_type \opd + .if rdpid_opd_type == REG_TYPE_R64 + R64_NUM rdpid_opd \opd + .else + R32_NUM rdpid_opd \opd + .endif + .byte 0xf3 + .if rdpid_opd > 7 + PFX_REX rdpid_opd 0 + .endif + .byte 0x0f, 0xc7 + MODRM 0xc0 rdpid_opd 0x7 +.endm #endif #endif -- 2.19.1
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