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			ASIDs have always been stored as unsigned longs, ie. 32 bits on MIPS32
kernels. This is problematic because it is feasible for the ASID version
to overflow & wrap around to zero.
We currently attempt to handle this overflow by simply setting the ASID
version to 1, using asid_first_version(), but we make no attempt to
account for the fact that there may be mm_structs with stale ASIDs that
have versions which we now reuse due to the overflow & wrap around.
Encountering this requires that:
  1) A struct mm_struct X is active on CPU A using ASID (V,n).
  2) That mm is not used on CPU A for the length of time that it takes
     for CPU A's asid_cache to overflow & wrap around to the same
     version V that the mm had in step 1. During this time tasks using
     the mm could either be sleeping or only scheduled on other CPUs.
  3) Some other mm Y becomes active on CPU A and is allocated the same
     ASID (V,n).
  4) mm X now becomes active on CPU A again, and now incorrectly has the
     same ASID as mm Y.
Where struct mm_struct ASIDs are represented above in the format
(version, EntryHi.ASID), and on a typical MIPS32 system version will be
24 bits wide & EntryHi.ASID will be 8 bits wide.
The length of time required in step 2 is highly dependent upon the CPU &
workload, but for a hypothetical 2GHz CPU running a workload which
generates a new ASID every 10000 cycles this period is around 248 days.
Due to this long period of time & the fact that tasks need to be
scheduled in just the right (or wrong, depending upon your inclination)
way, this is obviously a difficult bug to encounter but it's entirely
possible as evidenced by reports.
In order to fix this, simply extend ASIDs to 64 bits even on MIPS32
builds. This will extend the period of time required for the
hypothetical system above to encounter the problem from 28 days to
around 3 trillion years, which feels safely outside of the realms of
possibility.
The cost of this is slightly more generated code in some commonly
executed paths, but this is pretty minimal:
                         | Code Size Gain | Percentage
  -----------------------|----------------|-------------
    decstation_defconfig |           +270 | +0.00%
        32r2el_defconfig |           +652 | +0.01%
        32r6el_defconfig |          +1000 | +0.01%
I have been unable to measure any change in performance of the LMbench
lat_ctx or lat_proc tests resulting from the 64b ASIDs on either
32r2el_defconfig+interAptiv or 32r6el_defconfig+I6500 systems.
Signed-off-by: Paul Burton <paul.burton@mips.com>
Suggested-by: James Hogan <jhogan@kernel.org>
References: https://lore.kernel.org/linux-mips/80B78A8B8FEE6145A87579E8435D78C30205D5F3@fzex.ruijie.com.cn/
References: https://lore.kernel.org/linux-mips/1488684260-18867-1-git-send-email-jiwei.sun@windriver.com/
Cc: Jiwei Sun <jiwei.sun@windriver.com>
Cc: Yu Huabing <yhb@ruijie.com.cn>
Cc: stable@vger.kernel.org # 2.6.12+
Cc: linux-mips@vger.kernel.org
		
	
			
		
			
				
	
	
		
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			210 lines
		
	
	
	
		
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| /*
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|  * This file is subject to the terms and conditions of the GNU General Public
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|  * License.  See the file "COPYING" in the main directory of this archive
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|  * for more details.
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|  *
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|  * Copyright (C) 1994 Waldorf GMBH
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|  * Copyright (C) 1995, 1996, 1997, 1998, 1999, 2001, 2002, 2003 Ralf Baechle
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|  * Copyright (C) 1996 Paul M. Antoine
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|  * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
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|  * Copyright (C) 2004  Maciej W. Rozycki
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|  */
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| #ifndef __ASM_CPU_INFO_H
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| #define __ASM_CPU_INFO_H
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| 
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| #include <linux/cache.h>
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| #include <linux/types.h>
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| 
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| #include <asm/mipsregs.h>
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| 
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| /*
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|  * Descriptor for a cache
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|  */
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| struct cache_desc {
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| 	unsigned int waysize;	/* Bytes per way */
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| 	unsigned short sets;	/* Number of lines per set */
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| 	unsigned char ways;	/* Number of ways */
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| 	unsigned char linesz;	/* Size of line in bytes */
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| 	unsigned char waybit;	/* Bits to select in a cache set */
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| 	unsigned char flags;	/* Flags describing cache properties */
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| };
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| 
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| struct guest_info {
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| 	unsigned long		ases;
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| 	unsigned long		ases_dyn;
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| 	unsigned long long	options;
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| 	unsigned long long	options_dyn;
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| 	int			tlbsize;
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| 	u8			conf;
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| 	u8			kscratch_mask;
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| };
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| 
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| /*
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|  * Flag definitions
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|  */
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| #define MIPS_CACHE_NOT_PRESENT	0x00000001
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| #define MIPS_CACHE_VTAG		0x00000002	/* Virtually tagged cache */
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| #define MIPS_CACHE_ALIASES	0x00000004	/* Cache could have aliases */
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| #define MIPS_CACHE_IC_F_DC	0x00000008	/* Ic can refill from D-cache */
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| #define MIPS_IC_SNOOPS_REMOTE	0x00000010	/* Ic snoops remote stores */
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| #define MIPS_CACHE_PINDEX	0x00000020	/* Physically indexed cache */
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| 
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| struct cpuinfo_mips {
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| 	u64			asid_cache;
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| #ifdef CONFIG_MIPS_ASID_BITS_VARIABLE
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| 	unsigned long		asid_mask;
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| #endif
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| 
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| 	/*
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| 	 * Capability and feature descriptor structure for MIPS CPU
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| 	 */
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| 	unsigned long		ases;
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| 	unsigned long long	options;
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| 	unsigned int		udelay_val;
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| 	unsigned int		processor_id;
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| 	unsigned int		fpu_id;
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| 	unsigned int		fpu_csr31;
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| 	unsigned int		fpu_msk31;
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| 	unsigned int		msa_id;
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| 	unsigned int		cputype;
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| 	int			isa_level;
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| 	int			tlbsize;
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| 	int			tlbsizevtlb;
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| 	int			tlbsizeftlbsets;
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| 	int			tlbsizeftlbways;
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| 	struct cache_desc	icache; /* Primary I-cache */
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| 	struct cache_desc	dcache; /* Primary D or combined I/D cache */
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| 	struct cache_desc	vcache; /* Victim cache, between pcache and scache */
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| 	struct cache_desc	scache; /* Secondary cache */
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| 	struct cache_desc	tcache; /* Tertiary/split secondary cache */
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| 	int			srsets; /* Shadow register sets */
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| 	int			package;/* physical package number */
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| 	unsigned int		globalnumber;
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| #ifdef CONFIG_64BIT
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| 	int			vmbits; /* Virtual memory size in bits */
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| #endif
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| 	void			*data;	/* Additional data */
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| 	unsigned int		watch_reg_count;   /* Number that exist */
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| 	unsigned int		watch_reg_use_cnt; /* Usable by ptrace */
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| #define NUM_WATCH_REGS 4
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| 	u16			watch_reg_masks[NUM_WATCH_REGS];
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| 	unsigned int		kscratch_mask; /* Usable KScratch mask. */
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| 	/*
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| 	 * Cache Coherency attribute for write-combine memory writes.
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| 	 * (shifted by _CACHE_SHIFT)
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| 	 */
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| 	unsigned int		writecombine;
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| 	/*
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| 	 * Simple counter to prevent enabling HTW in nested
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| 	 * htw_start/htw_stop calls
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| 	 */
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| 	unsigned int		htw_seq;
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| 
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| 	/* VZ & Guest features */
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| 	struct guest_info	guest;
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| 	unsigned int		gtoffset_mask;
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| 	unsigned int		guestid_mask;
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| 	unsigned int		guestid_cache;
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| } __attribute__((aligned(SMP_CACHE_BYTES)));
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| 
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| extern struct cpuinfo_mips cpu_data[];
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| #define current_cpu_data cpu_data[smp_processor_id()]
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| #define raw_current_cpu_data cpu_data[raw_smp_processor_id()]
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| #define boot_cpu_data cpu_data[0]
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| 
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| extern void cpu_probe(void);
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| extern void cpu_report(void);
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| 
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| extern const char *__cpu_name[];
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| #define cpu_name_string()	__cpu_name[raw_smp_processor_id()]
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| 
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| struct seq_file;
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| struct notifier_block;
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| 
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| extern int register_proc_cpuinfo_notifier(struct notifier_block *nb);
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| extern int proc_cpuinfo_notifier_call_chain(unsigned long val, void *v);
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| 
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| #define proc_cpuinfo_notifier(fn, pri)					\
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| ({									\
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| 	static struct notifier_block fn##_nb = {			\
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| 		.notifier_call = fn,					\
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| 		.priority = pri						\
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| 	};								\
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| 									\
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| 	register_proc_cpuinfo_notifier(&fn##_nb);			\
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| })
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| 
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| struct proc_cpuinfo_notifier_args {
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| 	struct seq_file *m;
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| 	unsigned long n;
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| };
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| 
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| static inline unsigned int cpu_cluster(struct cpuinfo_mips *cpuinfo)
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| {
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| 	/* Optimisation for systems where multiple clusters aren't used */
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| 	if (!IS_ENABLED(CONFIG_CPU_MIPSR6))
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| 		return 0;
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| 
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| 	return (cpuinfo->globalnumber & MIPS_GLOBALNUMBER_CLUSTER) >>
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| 		MIPS_GLOBALNUMBER_CLUSTER_SHF;
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| }
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| 
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| static inline unsigned int cpu_core(struct cpuinfo_mips *cpuinfo)
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| {
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| 	return (cpuinfo->globalnumber & MIPS_GLOBALNUMBER_CORE) >>
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| 		MIPS_GLOBALNUMBER_CORE_SHF;
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| }
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| 
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| static inline unsigned int cpu_vpe_id(struct cpuinfo_mips *cpuinfo)
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| {
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| 	/* Optimisation for systems where VP(E)s aren't used */
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| 	if (!IS_ENABLED(CONFIG_MIPS_MT_SMP) && !IS_ENABLED(CONFIG_CPU_MIPSR6))
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| 		return 0;
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| 
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| 	return (cpuinfo->globalnumber & MIPS_GLOBALNUMBER_VP) >>
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| 		MIPS_GLOBALNUMBER_VP_SHF;
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| }
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| 
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| extern void cpu_set_cluster(struct cpuinfo_mips *cpuinfo, unsigned int cluster);
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| extern void cpu_set_core(struct cpuinfo_mips *cpuinfo, unsigned int core);
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| extern void cpu_set_vpe_id(struct cpuinfo_mips *cpuinfo, unsigned int vpe);
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| 
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| static inline bool cpus_are_siblings(int cpua, int cpub)
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| {
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| 	struct cpuinfo_mips *infoa = &cpu_data[cpua];
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| 	struct cpuinfo_mips *infob = &cpu_data[cpub];
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| 	unsigned int gnuma, gnumb;
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| 
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| 	if (infoa->package != infob->package)
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| 		return false;
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| 
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| 	gnuma = infoa->globalnumber & ~MIPS_GLOBALNUMBER_VP;
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| 	gnumb = infob->globalnumber & ~MIPS_GLOBALNUMBER_VP;
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| 	if (gnuma != gnumb)
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| 		return false;
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| 
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| 	return true;
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| }
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| 
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| static inline unsigned long cpu_asid_inc(void)
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| {
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| 	return 1 << CONFIG_MIPS_ASID_SHIFT;
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| }
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| 
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| static inline unsigned long cpu_asid_mask(struct cpuinfo_mips *cpuinfo)
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| {
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| #ifdef CONFIG_MIPS_ASID_BITS_VARIABLE
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| 	return cpuinfo->asid_mask;
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| #endif
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| 	return ((1 << CONFIG_MIPS_ASID_BITS) - 1) << CONFIG_MIPS_ASID_SHIFT;
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| }
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| 
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| static inline void set_cpu_asid_mask(struct cpuinfo_mips *cpuinfo,
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| 				     unsigned long asid_mask)
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| {
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| #ifdef CONFIG_MIPS_ASID_BITS_VARIABLE
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| 	cpuinfo->asid_mask = asid_mask;
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| #endif
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| }
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| 
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| #endif /* __ASM_CPU_INFO_H */
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