Re: [Qemu-devel] [PATCH] Bug Fix:Segmentation fault when use usb-ehci device

["Andreas Färber" <afaerber@suse.de>]

Hi,

Am 18.07.2013 17:27, schrieb Mike Qiu:
> Hi all
> 
> Any comments ?

You should've CCed the USB maintainer whose file you are touching for
review rather than just ppc people, see ./MAINTAINERS.

There's some typos in the commit message, but the change looks okay to
me - although there were discussions to catch this on the memory API
side of things instead.

Regards,
Andreas

> 
> Thanks
> Mike
> 2013/7/16 11:50, Mike Qiu wrote:
>> For usb-ehci in qemu, its caps just has read() operation,
>> the write() operation does not exist.
>>
>> This cause a Segmentation fault when use usb-ehci device in ppc64
>> platform.
>>
>> here is gdb output:
>>
>> Program received signal SIGSEGV, Segmentation fault.
>> [Switching to Thread 0x3fffa7fcef20 (LWP 6793)]
>> 0x00000000103f5244 in memory_region_oldmmio_write_accessor
>> (opaque=0x113e9e78, addr=9, value=0x3fffa7fce088,
>> size=1, shift=0, mask=255) at /home/Mike/qemu-impreza/memory.c:384
>> 384  mr->ops->old_mmio.write[ctz32(size)](mr->opaque, addr, tmp);
>> (gdb) p *mr->ops
>> $1 = {read = @0x10716f68: 0x1020699c <ehci_caps_read>, write = 0,
>>    endianness = DEVICE_LITTLE_ENDIAN, valid = {min_access_size = 1,
>>    max_access_size = 4, unaligned = false, accepts = 0}, impl =
>>    {min_access_size = 1, max_access_size = 1, unaligned = false},
>>    old_mmio = {read = {0, 0, 0}, write = {0, 0, 0}}}
>>
>> Becasue function write() of mr->ops has not been implement, in
>> function memory_region_dispatch_write(), it call
>> oldmmio write accessor, but at the same time old_mmio still not
>> been implement by default.
>>
>> That is the root cause of the Segmentation fault.
>>
>> To solve this problem, add empty function: ehci_caps_write()
>>
>> Signed-off-by: Mike Qiu <qiudayu@linux.vnet.ibm.com>
>> ---
>>  hw/usb/hcd-ehci.c |    7 +++++++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/hw/usb/hcd-ehci.c b/hw/usb/hcd-ehci.c
>> index 67e4b24..6c8a439 100644
>> --- a/hw/usb/hcd-ehci.c
>> +++ b/hw/usb/hcd-ehci.c
>> @@ -1072,6 +1072,12 @@ static void ehci_port_write(void *ptr, hwaddr addr,
>>      trace_usb_ehci_portsc_change(addr + s->portscbase, addr >> 2, *portsc, old);
>>  }
>>
>> +static void ehci_caps_write(void *ptr, hwaddr addr, uint64_t val,
>> +                           unsigned size)
>> +{
>> +    /* nothing */
>> +}
>> +
>>  static void ehci_opreg_write(void *ptr, hwaddr addr,
>>                               uint64_t val, unsigned size)
>>  {
>> @@ -2380,6 +2386,7 @@ static void ehci_frame_timer(void *opaque)
>>
>>  static const MemoryRegionOps ehci_mmio_caps_ops = {
>>      .read = ehci_caps_read,
>> +    .write = ehci_caps_write,
>>      .valid.min_access_size = 1,
>>      .valid.max_access_size = 4,
>>      .impl.min_access_size = 1,
> 
> 


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