timestamp - time of executing block in qemu -


i want ask question getting time information when executing translation block in qemu

in fact im using function

qemu_clock_get_ns(qemu_clock_virtual);

but i'm not sure returns time of executing translation block in guest processor.

so can give me hints ?

thanx

non kvm, soft-mmu qemu !!!:

qemu_clock_get_ns(qemuclocktype type) represent elapsed nano-seconds specified qemu reference clock. there several reference clocks: realtime, virtual, host, etc. qemu_clock_virtual counter explicitly driven qemu main loop: 1 tick of clock emulated quantum of time (nano-second).

details: qemu assume that:

1 guest instruction counter tick = 1 emulated nano second << icount_time_shift

icount_time_shift specfied "-icount" comand line option, 3 default.

all qemu timers implemented deadlines (in qemu_clock_virtual units), , qemu execute translation blocks 1 deadline another. straight conversation ns icount provide deteremenistic tb generation: qemu main loop advance clock accordance num of instructions executed @ translation block/chain (see cpu_exec.c, here abstract pseudo code):

cpu_exec(cpustate env):    # jump here if synchronous exception occurs: page fault, protection , etc   if(setjmp(env) == exeption)        ;#fall through    for(;;):     # if exception/interrupt pending handle here     take_exception_or_interrupt();      while(no_interrupts()) {         # num instructions left till next deadline         icount_extra = get_icount_limit();          # find/generate tb accordnace icount_extra         # every instruction access io last instruction @ block.         # if  access io cause interrupt handle on next iteration         tb = find_tb(env, icount_extra);          # execute tb or tb chain         execute(env, tb);          # increment qemu_clock_virtual accordance guest instructions executed         # (syncronise iothread)         update_clock(tb.executed_instr);         # take interrupts @ next iteration

intervals provided qemu_clock_virtual used @ models of guest timers/counters: example if set board system counter frequency 62 mhz, qemu single increment of counter per 16 increments of qemu_clock_virtual.

then can use qemu_clock_get_ns(qemu_clock_virtual) obtain emulated nano second intervals @ guest model.


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