Re: [RFC PATCH 1/1] QEMU plugin interface extension

[Florian Hauschild]

Am 21.08.21 um 15:18 schrieb Peter Maydell:
> On Sat, 21 Aug 2021 at 10:48, Florian Hauschild
> <florian.hauschild@fs.ei.tum.de> wrote:
>>
>> This extension covers functions:
>>   * to read and write guest memory
>>   * to read and write guest registers
>>   * to flush tb cache
>>   * to control single stepping of qemu from plugin
>>
>> These changes allow the user to
>>   * collect more information about the behaviour of the system
>>   * change the guest state with a plugin during execution
>>   * control cache of tcg
>>   * allow for precise instrumentation in execution flow
> 
>> +
>> +static int plugin_read_register(CPUState *cpu, GByteArray *buf, int reg)
>> +{
>> +    CPUClass *cc = CPU_GET_CLASS(cpu);
>> +    if (reg < cc->gdb_num_core_regs) {
>> +        return cc->gdb_read_register(cpu, buf, reg);
>> +    }
>> +    return 0;
>> +}
> 
> At the point where these functions execute is the emulation
> definitely stopped (ie no register values currently held
> live in TCG locals) ?
> 
> -- PMM
> 
I am not sure, if it is definitely stopped.
I call them during tb_exec_cb and insn_exec_cb.
I have used the extension on ARM and RISC-V single cpu guests and the
data collected is the one i would expect during normal execution on real
hardware. How this would behave on a multi cpu/core system i have not
tested yet.

Currently i am looking into this and as soon as i have found an answer i
will write back again.

Regards
Florian