Re: [Qemu-devel] [PATCH 12/18] Insert event_tap_mmio() to cpu_physical_memory_rw() in exec.c.

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2011-04-26 16:24, "大村 圭" wrote:
> 
> 2011/4/25 Jan Kiszka <jan.kiszka@web.de>:
>> On 2011-04-25 13:00, OHMURA Kei wrote:
>>> From: Yoshiaki Tamura <tamura.yoshiaki@lab.ntt.co.jp>
>>>
>>> Record mmio write event to replay it upon failover.
>>>
>>> Signed-off-by: Yoshiaki Tamura <tamura.yoshiaki@lab.ntt.co.jp>
>>> Signed-off-by: OHMURA Kei <ohmura.kei@lab.ntt.co.jp>
>>> ---
>>>  exec.c |    4 ++++
>>>  1 files changed, 4 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/exec.c b/exec.c
>>> index c3dc68a..3c3cece 100644
>>> --- a/exec.c
>>> +++ b/exec.c
>>> @@ -33,6 +33,7 @@
>>>  #include "osdep.h"
>>>  #include "kvm.h"
>>>  #include "qemu-timer.h"
>>> +#include "event-tap.h"
>>>  #if defined(CONFIG_USER_ONLY)
>>>  #include <qemu.h>
>>>  #include <signal.h>
>>> @@ -3736,6 +3737,9 @@ void cpu_physical_memory_rw(target_phys_addr_t addr, uint8_t *buf,
>>>                  io_index = (pd >> IO_MEM_SHIFT) & (IO_MEM_NB_ENTRIES - 1);
>>>                  if (p)
>>>                      addr1 = (addr & ~TARGET_PAGE_MASK) + p->region_offset;
>>> +
>>> +                event_tap_mmio(addr, buf, len);
>>> +
>>
>> You know that this is incomplete? A few devices are calling st*_phys
>> directly, specifically virtio.
>>
>> What kind of mmio should be traced here, device or CPU originated? Or both?
>>
>> Jan
>>
>>
> 
> To let Kemari replay outputs upon failover, tracing CPU originated
> mmio (specifically write requests) should be enough.
> IIUC, we can reproduce device originated mmio as a result of cpu
> originated mmio.
> 

OK, I see.

But this tap will only work for KVM. I think you either have to catch
the other paths that TCG could take as well or maybe better move the
hook into kvm-all - then it's absolutely clear that this is no generic
feature.

Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux