[Skiboot] [PATCH-RESEND] capi: Disable CAPP virtual machines

[christophe lombard]

Le 01/02/2018 à 09:29, Stewart Smith a écrit :
> christophe lombard <clombard at linux.vnet.ibm.com> writes:
>> Le 18/01/2018 à 05:09, Vaibhav Jain a écrit :
>>> When exercising more than one CAPI accelerators simultaneously in
>>> cache coherency mode, the verification team is seeing a deadlock. To
>>> fix this a workaround of disabling CAPP virtual machines is
>>> suggested. These 'virtual machines' let PSL queue multiple CAPP
>>> commands for servicing by CAPP there by increasing
>>> throughput. Below is the error scenario described by the h/w team:
>>>
>>> " With virtual machines enabled we had a deadlock scenario where with 2
>>> or more CAPI's in a system you could get in a deadlock scenario due to
>>> cast-outs that are required break the deadlock (evict lines that
>>> another CAPI is requesting) get stuck in the virtual machine queue by
>>> a command ahead of it that is being retried by the same scenario in
>>> the other CAPI. "
>>>
>>> So this patch updates CAPP APC Master Powerbus control
>>> register during CAPP init to also set Bit(12) that disables CAPP
>>> virtual machines. This forces processing of CAPP commands from PSL one
>>> at a time and thereby preventing above mentioned deadlock scenario.
>>>
>>> Signed-off-by: Vaibhav Jain <vaibhav at linux.vnet.ibm.com>
>>> ---
>>> Change-log:
>>> Resend -> Updated the patch description with more info CAPP virtual
>>>          	  machines and the error scenario.
>>> ---
>>>    hw/phb4.c | 1 +
>>>    1 file changed, 1 insertion(+)
>>>
>>> diff --git a/hw/phb4.c b/hw/phb4.c
>>> index ff912e1f..8e660b66 100644
>>> --- a/hw/phb4.c
>>> +++ b/hw/phb4.c
>>> @@ -3581,6 +3581,7 @@ static void phb4_init_capp_regs(struct phb4 *p, uint32_t capp_eng)
>>>    	xscom_read(p->chip_id, APC_MASTER_PB_CTRL + offset, &reg);
>>>    	reg |= PPC_BIT(0); /* enable cResp exam */
>>>    	reg |= PPC_BIT(3); /* disable vg not sys */
>>> +	reg |= PPC_BIT(12);/* HW417025: disable capp virtual machines */
>>>    	if (p->rev == PHB4_REV_NIMBUS_DD10) {
>>>    		reg |= PPC_BIT(1);
>>>    	} else {
>>>
>>
>> Acked-by: Christophe Lombard clombard at linux.vnet.ibm.com
> 
> You seem to be missing the < > around the email address, which caused
> patchwork not to pick up the acked-by. Might want to fix that :)
> 

Oups, sorry about that. I will check this point.