Re: [PATCH v15 07/10] tb-stats: Adding info [tb-list|tb] commands to HMP (WIP)

[Wu, Fei]

On 6/12/2023 3:17 PM, Richard Henderson wrote:
> On 6/12/23 03:44, Wu, Fei wrote:
>> On 6/7/2023 8:24 PM, Fei Wu wrote:
>>> +void hmp_info_tb(Monitor *mon, const QDict *qdict)
>>> +{
>>> +    const int id = qdict_get_int(qdict, "id");
>>> +    g_autoptr(GString) buf = g_string_new("");
>>> +
>>> +    if (!tcg_enabled()) {
>>> +        monitor_printf(mon, "Only available with accel=tcg\n");
>>> +        return;
>>> +    }
>>> +
>>> +    TBStatistics *tbs = get_tbstats_by_id(id);
>>> +    if (tbs == NULL) {
>>> +        monitor_printf(mon, "TB %d information is not recorded\n", id);
>>> +        return;
>>> +    }
>>> +
>>> +    monitor_printf(mon, "\n------------------------------\n\n");
>>> +
>>> +    int valid_tb_num = dump_tb_info(buf, tbs, id);
>>> +    monitor_printf(mon, "%s", buf->str);
>>> +
>>> +    if (valid_tb_num > 0) {
>>> +        unsigned num_inst = tbs->code.num_guest_inst /
>>> tbs->translations.total;
>>> +
>>> +        monitor_printf(mon, "\n----------------n\n");
>>> +        // FIXME: cannot disas
>>> +        monitor_disas(mon, mon_get_cpu(mon), tbs->phys_pc, num_inst,
>>> true);
>>> +        monitor_printf(mon, "\n------------------------------\n\n");
>>> +    }
>>> +}
>>> +
>> So far the following methods are candidates for monitor_disas:
>>
>> 1. still use ram_addr_t for tbs->phys_pc, and extend monitor_disas to
>> support disassemble ram_addr_t by using qemu_map_ram_ptr(NULL, ram_addr)
>> to convert it to hva first
>>
>> 2. use gpa for tbs->phys_pc, there is no need to change monitor_disas,
>> but add another parameter for get_page_addr_code_hostp() to return extra
>> gpa, probe_access_internal() has already returned CPUTLBEntryFull, so
>> it's plain to get gpa here.
> 
> No, we need the ram_addr_t for dirty-page handling in order to detect
> self-modifying code.  Leave tb->phys_pc alone.
> 
I mean return both ram_addr_t and gpa from get_page_addr_code_hostp(),
tb->phys_pc will not be changed, I'm not going to change tbs->phys_pc
either (like #3), the extra gpa will be saved in tbs for 'info tb' purpose.

In short, no change on phys_pc, but add gpa to tbs, sounds good?

Thanks,
Fei.

> 
> r~
> 
>>
>> 3. record gpa in another field of tbs, and keep tbs->phys_pc as it is,
>> this is just a variation of #2.
>>
>> I'm inclined to use method #2. I think gpa carries more information for
>> debugging than ram_addr_t, guest can map gpa to the executable file
>> etc., but it has little knowledge of ram_addr_t.
>>
>> What do you suggest?
>>
>> Thanks,
>> Fei.
>>
>