Re: [PATCH v2] hw/scsi/lsi53c895a: add timer to scripts processing

[Sven Schnelle <svens@stackframe.org>]

Peter Maydell <peter.maydell@linaro.org> writes:

> On Thu, 29 Feb 2024 at 20:44, Sven Schnelle <svens@stackframe.org> wrote:
>>
>> HP-UX 10.20 seems to make the lsi53c895a spinning on a memory location
>> under certain circumstances. As the SCSI controller and CPU are not
>> running at the same time this loop will never finish. After some
>> time, the check loop interrupts with a unexpected device disconnect.
>> This works, but is slow because the kernel resets the scsi controller.
>> Instead of signaling UDC, start a timer and exit the loop. Until the
>> timer fires, the CPU can process instructions which might changes the
>> memory location.
>>
>> The limit of instructions is also reduced because scripts running on
>> the SCSI processor are usually very short. This keeps the time until
>> the loop is exit short.
>
> "exited"
>
>>
>> Suggested-by: Peter Maydell <peter.maydell@linaro.org>
>> Signed-off-by: Sven Schnelle <svens@stackframe.org>
>> ---
>> Changes in v2:
>> - update comment in lsi_execute_script()
>> - reset waiting state and del timer in lsi_execute_script() to
>>   handle the case where script processing is triggered via
>>   register write, and not from the pending timer
>> - delete timer in lsi_scsi_exit()
>
> Other than the s/host/guest/ comment fix,
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
>
> I don't suppose anybody has a setup with the Windows drivers
> to test this on? (commit ee4d919f30f13 suggests that at least
> Windows XP and 2003 had this problem.)

I have a Windows XP VM with lsi53c895a. I just fired it up and added
a qemu_log() in the timer path, and seen it trigger once while copying
a few files. It looks like Windows XP (or better the SCSI driver) also
works with this patch.