diff options
| author | WANG Xuerui <git@xen0n.name> | 2020-05-23 21:37:01 +0800 |
|---|---|---|
| committer | Thomas Bogendoerfer <tsbogend@alpha.franken.de> | 2020-05-24 09:26:55 +0200 |
| commit | ec7a93188a75b57b9f704db6862e7137f01aa80b (patch) | |
| tree | 84907800878283ad5358796589613757ed9783f2 /arch/mips/kernel/traps.c | |
| parent | 8267e78f020a8de2752754c42ec1d56e92431477 (diff) | |
MIPS: emulate CPUCFG instruction on older Loongson64 cores
CPUCFG is the instruction for querying processor characteristics on
newer Loongson processors, much like CPUID of x86. Since the instruction
is supposedly designed to provide a unified way to do feature detection
(without having to, for example, parse /proc/cpuinfo which is too
heavyweight), it is important to provide compatibility for older cores
without native support. Fortunately, most of the fields can be
synthesized without changes to semantics. Performance is not really big
a concern, because feature detection logic is not expected to be
invoked very often in typical userland applications.
The instruction can't be emulated on LOONGSON_2EF cores, according to
FlyGoat's experiments. Because the LWC2 opcode is assigned to other
valid instructions on 2E and 2F, no RI exception is raised for us to
intercept. So compatibility is only extended back furthest to
Loongson-3A1000. Loongson-2K is covered too, as it is basically a remix
of various blocks from the 3A/3B models from a kernel perspective.
This is lightly based on Loongson's work on their Linux 3.10 fork, for
being the authority on the right feature flags to fill in, where things
aren't otherwise discoverable.
Signed-off-by: WANG Xuerui <git@xen0n.name>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: Huacai Chen <chenhc@lemote.com>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Diffstat (limited to 'arch/mips/kernel/traps.c')
| -rw-r--r-- | arch/mips/kernel/traps.c | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c index 89eb82f6c837..2d5b16daf331 100644 --- a/arch/mips/kernel/traps.c +++ b/arch/mips/kernel/traps.c @@ -71,6 +71,8 @@ #include <asm/tlbex.h> #include <asm/uasm.h> +#include <asm/mach-loongson64/cpucfg-emul.h> + extern void check_wait(void); extern asmlinkage void rollback_handle_int(void); extern asmlinkage void handle_int(void); @@ -693,6 +695,44 @@ static int simulate_sync(struct pt_regs *regs, unsigned int opcode) return -1; /* Must be something else ... */ } +/* + * Loongson-3 CSR instructions emulation + */ + +#ifdef CONFIG_CPU_LOONGSON3_CPUCFG_EMULATION + +#define LWC2 0xc8000000 +#define RS BASE +#define CSR_OPCODE2 0x00000118 +#define CSR_OPCODE2_MASK 0x000007ff +#define CSR_FUNC_MASK RT +#define CSR_FUNC_CPUCFG 0x8 + +static int simulate_loongson3_cpucfg(struct pt_regs *regs, + unsigned int opcode) +{ + int op = opcode & OPCODE; + int op2 = opcode & CSR_OPCODE2_MASK; + int csr_func = (opcode & CSR_FUNC_MASK) >> 16; + + if (op == LWC2 && op2 == CSR_OPCODE2 && csr_func == CSR_FUNC_CPUCFG) { + int rd = (opcode & RD) >> 11; + int rs = (opcode & RS) >> 21; + __u64 sel = regs->regs[rs]; + + perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, 0); + + regs->regs[rd] = loongson3_cpucfg_read_synthesized( + ¤t_cpu_data, sel); + + return 0; + } + + /* Not ours. */ + return -1; +} +#endif /* CONFIG_CPU_LOONGSON3_CPUCFG_EMULATION */ + asmlinkage void do_ov(struct pt_regs *regs) { enum ctx_state prev_state; @@ -1166,6 +1206,11 @@ no_r2_instr: if (status < 0) status = simulate_fp(regs, opcode, old_epc, old31); + +#ifdef CONFIG_CPU_LOONGSON3_CPUCFG_EMULATION + if (status < 0) + status = simulate_loongson3_cpucfg(regs, opcode); +#endif } else if (cpu_has_mmips) { unsigned short mmop[2] = { 0 }; |