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SubjectRe: [PATCH kernel v3 2/2] powerpc/dma: Fallback to dma_ops when persistent memory present
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On 29/10/2020 11:40, Michael Ellerman wrote:
> Alexey Kardashevskiy <aik@ozlabs.ru> writes:
>> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
>> index e4198700ed1a..91112e748491 100644
>> --- a/arch/powerpc/platforms/pseries/iommu.c
>> +++ b/arch/powerpc/platforms/pseries/iommu.c
>> @@ -1111,11 +1112,13 @@ static void reset_dma_window(struct pci_dev *dev, struct device_node *par_dn)
>> */
>> static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
>> {
>> - int len, ret;
>> + int len = 0, ret;
>> + bool pmem_present = of_find_node_by_type(NULL, "ibm,pmemory") != NULL;
>
> That leaks a reference on the returned node.
>
> dn = of_find_node_by_type(NULL, "ibm,pmemory");
> pmem_present = dn != NULL;
> of_node_put(dn);


ah, true. v4 then.


>
>
>> @@ -1126,7 +1129,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
>>
>> mutex_lock(&direct_window_init_mutex);
>>
>> - dma_addr = find_existing_ddw(pdn);
>> + dma_addr = find_existing_ddw(pdn, &len);
>
> I don't see len used anywhere?
>
>> if (dma_addr != 0)
>> goto out_unlock;
>>
>> @@ -1212,14 +1215,26 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
>> }
>> /* verify the window * number of ptes will map the partition */
>> /* check largest block * page size > max memory hotplug addr */
>> - max_addr = ddw_memory_hotplug_max();
>> - if (query.largest_available_block < (max_addr >> page_shift)) {
>> - dev_dbg(&dev->dev, "can't map partition max 0x%llx with %llu "
>> - "%llu-sized pages\n", max_addr, query.largest_available_block,
>> - 1ULL << page_shift);
>> + /*
>> + * The "ibm,pmemory" can appear anywhere in the address space.
>> + * Assuming it is still backed by page structs, try MAX_PHYSMEM_BITS
>> + * for the upper limit and fallback to max RAM otherwise but this
>> + * disables device::dma_ops_bypass.
>> + */
>> + len = max_ram_len;
>
> Here you override whatever find_existing_ddw() wrote to len?


Not always, there is a bunch of gotos before this line to the end of the
function and one (which returns the existing window) is legit. Thanks,



>
>> + if (pmem_present) {
>> + if (query.largest_available_block >=
>> + (1ULL << (MAX_PHYSMEM_BITS - page_shift)))
>> + len = MAX_PHYSMEM_BITS - page_shift;
>> + else
>> + dev_info(&dev->dev, "Skipping ibm,pmemory");
>> + }
>> +
>> + if (query.largest_available_block < (1ULL << (len - page_shift))) {
>> + dev_dbg(&dev->dev, "can't map partition max 0x%llx with %llu %llu-sized pages\n",
>> + 1ULL << len, query.largest_available_block, 1ULL << page_shift);
>> goto out_failed;
>> }
>> - len = order_base_2(max_addr);
>> win64 = kzalloc(sizeof(struct property), GFP_KERNEL);
>> if (!win64) {
>> dev_info(&dev->dev,
>
>
> cheers
>

--
Alexey

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