[Skiboot] [PATCH 2/2] npu2: Purge cache when resetting a GPU

[Reza Arbab]

On Tue, Jun 11, 2019 at 12:55:48PM +1000, Alexey Kardashevskiy wrote:
>On 08/06/2019 02:08, Reza Arbab wrote:
>> After putting all a GPU's links in reset, do a cache purge in case we
>> have CPU cache lines belonging to the now-unaccessible GPU memory.
>>
>> Fixes: 68d11e4460ec ("npu2: Reset NVLinks when resetting a GPU")
>> Cc: skiboot-stable at lists.ozlabs.org
>> Signed-off-by: Reza Arbab <arbab at linux.ibm.com>
>> ---
>>  hw/npu2.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/hw/npu2.c b/hw/npu2.c
>> index 774592911110..3a2808d7133c 100644
>> --- a/hw/npu2.c
>> +++ b/hw/npu2.c
>> @@ -561,6 +561,8 @@ static int64_t npu2_gpu_bridge_sec_bus_reset(void *dev,
>>
>>  	gpu = list_top(&pd->children, struct pci_device, link);
>>  	if (gpu && (*data & PCI_CFG_BRCTL_SECONDARY_RESET)) {
>> +		int64_t rc;
>> +
>>  		dt_for_each_compatible(dt_root, np, "ibm,power9-npu-pciex") {
>>  			npphb = pci_get_phb(dt_prop_get_cell(np,
>>  					"ibm,opal-phbid", 1));
>> @@ -574,6 +576,10 @@ static int64_t npu2_gpu_bridge_sec_bus_reset(void *dev,
>>  					npu2_dev_procedure_reset(ndev);
>>  			}
>>  		}
>> +
>> +		rc = purge_l2_l3_caches();
>> +		if (rc)
>> +			return rc;
>
>
>Ah, missed that :( Probably would make more sense to have this in
>npu2_dev_procedure_reset() as the other caller also purges caches.

That is tempting but we'd end up purging the cache a bunch of times, 
once for each link. Probably better to reset each link, and then just do 
one purge afterwards.

-- 
Reza Arbab