Re: [Qemu-devel] [PATCH v2 05/11] translate-all: exit cpu_restore_state early if translating

[Richard Henderson]

On 03/03/2017 06:53 AM, Alex Bennée wrote:
> The translation code uses cpu_ld*_code which can trigger a tlb_fill
> which if it fails will attempt a fault resolution. This never works
> during translation as the TB being generated hasn't been added yet.
> However with the new locking regime we end up double locking the
> tb_lock(). As the tcg_ctx.cpu is only set during translation we use
> this to short circuit the restore code and return with a fail.

We *should* have retaddr == 0 for this case, which indicates that we should not 
attempt to restore state.  Are you seeing a non-zero value?

Hmm.. Or rather we should not have called cpu_restore_state in the first place. 
 What is the call chain leading to this point?

Is this in fact linux-user, not softmmu, as you imply from tlb_fill?  Because 
handle_cpu_signal will in fact pass a genuine non-zero retaddr for the SIGSEGV 
resulting from a cpu_ld*_code from a non-mapped address.

So... for linux-user I think the qemu_log is unnecessary -- that's just the way 
things are.  For softmmu, I don't know what to think except that we shouldn't 
have gotten here.


r~