Re: [Qemu-devel] [PATCH v3 for-2.11 3/3] tpm_tis: Return 0 for every register in case of failure mode

[Marc-André Lureau]

Hi

On Wed, Nov 15, 2017 at 2:18 AM, Stefan Berger
<address@hidden> wrote:
> On 11/14/2017 06:47 PM, Marc-André Lureau wrote:
>>
>> Hi
>>
>> On Tue, Nov 14, 2017 at 10:52 PM, Stefan Berger
>> <address@hidden> wrote:
>>>
>>> Rather than returning ~0, return 0 for every register in case of
>>> failure mode. The '0' is better to indicate that there's no device
>>> there.
>>
>> For most registers, 0 makes more sense. However, I wonder if we
>> shouldn't just fail to start qemu in this case...
>>
>> Not convincing me this is 2.11 material either. Does this fix a specific
>> bug?
>
>
> Yes, SeaBIOS detects the ~0 when it probes and thinks there's a device
> there. It then hangs trying to set flags and read registers to be able to
> use the device.
>

Please update the commit message with that added,
Reviewed-by: Marc-André Lureau <address@hidden>


>    Stefan
>
>
>>
>>> Signed-off-by: Stefan Berger <address@hidden>
>>> ---
>>>   hw/tpm/tpm_tis.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/hw/tpm/tpm_tis.c b/hw/tpm/tpm_tis.c
>>> index fec2fc6..42d647d 100644
>>> --- a/hw/tpm/tpm_tis.c
>>> +++ b/hw/tpm/tpm_tis.c
>>> @@ -545,7 +545,7 @@ static uint64_t tpm_tis_mmio_read(void *opaque,
>>> hwaddr addr,
>>>       uint8_t v;
>>>
>>>       if (tpm_backend_had_startup_error(s->be_driver)) {
>>> -        return val;
>>> +        return 0;
>>>       }
>>>
>>>       switch (offset) {
>>> --
>>> 2.5.5
>>>
>>
>>
>



-- 
Marc-André Lureau