Re: [Qemu-devel] [PATCH v13 05/24] tcg: add options for enabling MTTCG

["Alex Bennée" <alex.bennee@linaro.org>]

Pranith Kumar <bobby.prani@gmail.com> writes:

> Hi Alex,
>
> On Wed, Feb 22, 2017 at 12:13 PM, Alex Bennée <alex.bennee@linaro.org> wrote:
>> From: KONRAD Frederic <fred.konrad@greensocs.com>
>>
>> We know there will be cases where MTTCG won't work until additional work
>> is done in the front/back ends to support. It will however be useful to
>> be able to turn it on.
>>
>> As a result MTTCG will default to off unless the combination is
>> supported. However the user can turn it on for the sake of testing.
>>
>> Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
>> [AJB: move to -accel tcg,thread=multi|single, defaults]
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> Reviewed-by: Richard Henderson <rth@twiddle.net>
>> ---
>> v1:
>>   - merge with add mttcg option.
>>   - update commit message
>> v2:
>>   - machine_init->opts_init
>> v3:
>>   - moved from -tcg to -accel tcg,thread=single|multi
>>   - fix checkpatch warnings
>> v4:
>>   - make mttcg_enabled extern, qemu_tcg_mttcg_enabled() now just macro
>>   - qemu_tcg_configure now propagates Error instead of exiting
>>   - better error checking of thread=foo
>>   - use CONFIG flags for default_mttcg_enabled()
>>   - disable mttcg with icount, error if both forced on
>> v7
>>   - explicitly disable MTTCG for TCG_OVERSIZED_GUEST
>>   - use check_tcg_memory_orders_compatible() instead of CONFIG_MTTCG_HOST
>>   - change CONFIG_MTTCG_TARGET to TARGET_SUPPORTS_MTTCG
>> v8
>>   - fix missing include tcg.h
>>   - change mismatched MOs to a warning instead of error
>> v10
>>   - TCG_DEFAULT_MO -> TCG_GUEST_DEFAULT_MO
>> v11
>>   - tweak warning message
>> ---
>>  cpus.c                | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++
>>  include/qom/cpu.h     |  9 +++++++
>>  include/sysemu/cpus.h |  2 ++
>>  qemu-options.hx       | 20 ++++++++++++++
>>  tcg/tcg.h             |  9 +++++++
>>  vl.c                  | 49 +++++++++++++++++++++++++++++++++-
>>  6 files changed, 161 insertions(+), 1 deletion(-)
>>
>> diff --git a/cpus.c b/cpus.c
>> index 0bcb5b50b6..c296ec715f 100644
>> --- a/cpus.c
>> +++ b/cpus.c
> <...>
>> +void qemu_tcg_configure(QemuOpts *opts, Error **errp)
>> +{
>> +    const char *t = qemu_opt_get(opts, "thread");
>> +    if (t) {
>> +        if (strcmp(t, "multi") == 0) {
>> +            if (TCG_OVERSIZED_GUEST) {
>> +                error_setg(errp, "No MTTCG when guest word size > hosts");
>> +            } else {
>> +                if (!check_tcg_memory_orders_compatible()) {
>> +                    error_report("Guest expects a stronger memory ordering than"
>> +                                 "the host provides");
>> +                    error_printf("This may cause strange/hard to debug errors");
>> +                }
>
> This prints it as:
>
> Guest expects a stronger memory ordering thanthe host provides
>
> Please add a space between 'than' and 'the'.

Will do.

> Also why are you using
> error_report() for the first line and error_printf() for the second?

There is only one error to report, quoth HACKING:

"Use error_printf() & friends to print additional information."

--
Alex Bennée