Re: [Qemu-devel] Problems with QEMU sdcard while using glib 2.33.8

[Paolo Bonzini <pbonzini@redhat.com>]

Il 19/09/2013 10:11, Stefan Hajnoczi ha scritto:
> On Thu, Sep 19, 2013 at 8:36 AM, Taimoor Mirza <taimoor.mrza@gmail.com> wrote:
> 
> Please use Reply-All to keep the CC list on your reply email.  This
> way others on the mailing list can follow the discussion and
> participate.
> 
>> O1 disassembly is at http://pastebin.com/yxWAmmmf
>>
>> O2 disassembly is at http://pastebin.com/v0uqHuYY
> 
> I diffed them.  The differences look reasonable, nothing obviously broken:
>  * The broken -O2 version inlines qemu_coroutine_switch() into
> coroutine_trampoline().
>  * The broken -O2 version changes the ordering of basic blocks and
> switches a few instructions for shorter/cheaper equivalents.
> 
> Taimoor: Can you try "make check" with the -O2 version?  In
> particular, the test-coroutine tests may fail and that could help us
> figure out which operation is broken.
> 
> Paolo: CCed you in case you want to diff the working -O1 against the
> broken -O2 disassembly.  Perhaps Taimoor's gcc 4.6.2 -O2 subtly breaks
> around the Windows Fiber API calls.

Taimoor, can you please try compiling coroutine-win32.c at
-O2 but without the -fstack-protector-all compiler option?  If it works,
please try with -fstack-protector instead of -fstack-protector-all.

Also (separately from the above experiment), can you try this patch and
see if it breaks/works at -O1 and -O2?  Then, independent of the result,
please post -O1 and -O2 assembly outputs with the patch.

diff --git a/coroutine-win32.c b/coroutine-win32.c
index edc1f72..3b10189 100644
--- a/coroutine-win32.c
+++ b/coroutine-win32.c
@@ -55,7 +55,13 @@ static void CALLBACK coroutine_trampoline(void *co_)
 
     while (true) {
         co->entry(co->entry_arg);
-        qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
+        Coroutine *to_ = co->caller;
+        CoroutineWin32 *from = DO_UPCAST(CoroutineWin32, base, co);
+        CoroutineWin32 *to = DO_UPCAST(CoroutineWin32, base, to_);
+
+        current = to_;
+        to->action = COROUTINE_TERMINATE;
+        SwitchToFiber(to->fiber);
     }
 }
 

Thanks,

Paolo