Hi Warner,
On 31/1/26 01:08, Warner Losh wrote:
OK. I've updated bsd-user fork from last year to yesterday. I had one
question.
I see that we've gone from tb_flush() to queue_tb_flush(). Why was that?
This fixed a race where a vCPU kept a ref to a flushed TB.
And is it a drop in?
FreeBSD's fork has this in the thread creation:
/*
* If this is our first additional thread, we need to ensure we
* generate code for parallel execution and flush old translations.
* Do this now so that the copy gets CF_PARALLEL too.
*/
if (!(cpu->tcg_cflags & CF_PARALLEL)) {
cpu->tcg_cflags |= CF_PARALLEL;
tb_flush(cpu);
}
I think the right thing to do is to just change this to
queue_tb_flush(cpu), and that compiles. I'd like to get some
confirmation, though. Did I parse the changes right?
You should change these 4 lines by:
begin_parallel_context(cpu);
which calls tb_flush__exclusive_or_serial(), itself described as:
* Used to flush all the translation blocks in the system. Mostly this
* is used to empty the code generation buffer after it is full.
* Sometimes it is used when it is simpler to flush everything than work
* out which individual translations are now invalid.
*
* Must be called from an exclusive or serial context, e.g.
* start_exclusive, vm_stop, or when there is only one vcpu. Note that
* start_exclusive cannot be called from within the cpu run loop, so
* this cannot be called from within target code.
See equivalent commit 430014bee7a ("linux-user: Split out
begin_parallel_context").
Everything else is mundane changes that were more annoying than difficult :)
This is reassuring :)
Warner
