Subject: Re: [PATCH V7 04/17] PCI: Take additional IOV BAR alignment in sizing and assigning

From: Wei Yang <[email-masked]>
Date: Thu, 28 Aug 2014 10:34:02 +0800

Bjorn,

Is my understanding correct? Could I send another version based on your
comment, so that we can see it meets your requirement? 

On Wed, Aug 20, 2014 at 02:14:02PM +0800, Wei Yang wrote:
>On Tue, Aug 19, 2014 at 09:08:41PM -0600, Bjorn Helgaas wrote:
>>On Thu, Jul 24, 2014 at 02:22:14PM +0800, Wei Yang wrote:
>>> At resource sizing/assigning stage, resources are divided into two lists,
>>> requested list and additional list, while the alignement of the additional
>>> IOV BAR is not taken into the sizeing and assigning procedure.
>>> 
>>> This is reasonable in the original implementation, since IOV BAR's alignment is
>>> mostly the size of a PF BAR alignemt. This means the alignment is already taken
>>> into consideration. While this rule may be violated on some platform.
>>> 
>>> This patch take the additional IOV BAR alignment in sizing and assigning stage
>>> explicitly.
>>> 
>>> Signed-off-by: Wei Yang <[email-masked]>
>>> ---
>>>  drivers/pci/setup-bus.c |   68 +++++++++++++++++++++++++++++++++++++++++------
>>>  1 file changed, 60 insertions(+), 8 deletions(-)
>>> 
>>> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
>>> index a5a63ec..d83681f 100644
>>> --- a/drivers/pci/setup-bus.c
>>> +++ b/drivers/pci/setup-bus.c
>>> @@ -120,6 +120,28 @@ static resource_size_t get_res_add_size(struct list_head *head,
>>>  	return 0;
>>>  }
>>>  
>>> +static resource_size_t get_res_add_align(struct list_head *head,
>>> +		struct resource *res)
>>> +{
>>> +	struct pci_dev_resource *dev_res;
>>> +
>>> +	list_for_each_entry(dev_res, head, list) {
>>> +		if (dev_res->res == res) {
>>> +			int idx = res - &dev_res->dev->resource[0];
>>> +
>>> +			dev_printk(KERN_DEBUG, &dev_res->dev->dev,
>>> +				   "res[%d]=%pR get_res_add_align min_align %llx\n",
>>> +				   idx, dev_res->res,
>>> +				   (unsigned long long)dev_res->min_align);
>>> +
>>> +			return dev_res->min_align;
>>> +		}
>>> +	}
>>> +
>>> +	return 0;
>>> +}
>>
>>I see that you copied the structure of the existing get_res_add_size()
>>here.  But I don't understand *that* function.  It looks basically like
>>this:
>>
>>  resource_size_t get_res_add_size(list, res)
>>  {
>>    list_for_each_entry(dev_res, head, list) {
>>      if (dev_res->res == res)
>>        return dev_res->add_size;
>>    }
>>    return 0;
>>  }
>>
>>and we call it like this:
>>
>>  dev_res->res->end += get_res_add_size(realloc_head, dev_res->res);
>>
>>So we start out with dev_res", pass in dev_res->res, search the
>>realloc_head list to find dev_res again, and return dev_res->add_size.
>>That looks equivalent to just:
>>
>>  dev_res->res->end += dev_res->add_size;
>>
>>It looks like get_res_add_size() merely adds a printk and some complexity.
>>Am I missing something?
>>
>
>Let me try to explain it, if not correct, please let know :-)
>
>  dev_res->res->end += get_res_add_size(realloc_head, dev_res->res);
>
>would be expanded to:
>
>  dev_res->res->end += dev_res_1->add_size;
>
>with the dev_res_1 is another one from dev_res which is stored in realloc_head.
>
>>I do see that there are other callers where we don't actually start with
>>dev_res, which makes it a little more complicated.  But I think you should
>>either add something like this:
>>
>>  struct pci_dev_resource *res_to_dev_res(list, res)
>>  {
>>    list_for_each_entry(dev_res, head, list) {
>>      if (dev_res->res == res)
>>        return dev_res;
>>    }
>>    return NULL;
>>  }
>>
>
>Ok, we can extract the common part of these two functions.
>
>>which can be used to replace get_res_add_size() and get_res_add_align(), OR
>>figure out whether the dev_res of interest is always one we've just added.
>>If it is, maybe you can just make add_to_list() return the dev_res pointer
>>instead of an errno, and hang onto the pointer.  I'd like that much better
>>if that's possible.
>>
>
>Sorry, I don't get this point.
>
>add_to_list() is used to create the pci_dev_resource list, get_res_add_size()
>and get_res_add_align() is to retrieve the information in the list. I am not
>sure how to leverage add_to_list() in these two functions?
>
>>> +
>>> +
>>>  /* Sort resources by alignment */
>>>  static void pdev_sort_resources(struct pci_dev *dev, struct list_head *head)
>>>  {
>>> @@ -368,8 +390,9 @@ static void __assign_resources_sorted(struct list_head *head,
>>>  	LIST_HEAD(save_head);
>>>  	LIST_HEAD(local_fail_head);
>>>  	struct pci_dev_resource *save_res;
>>> -	struct pci_dev_resource *dev_res, *tmp_res;
>>> +	struct pci_dev_resource *dev_res, *tmp_res, *dev_res2;
>>>  	unsigned long fail_type;
>>> +	resource_size_t add_align, align;
>>>  
>>>  	/* Check if optional add_size is there */
>>>  	if (!realloc_head || list_empty(realloc_head))
>>> @@ -384,10 +407,31 @@ static void __assign_resources_sorted(struct list_head *head,
>>>  	}
>>>  
>>>  	/* Update res in head list with add_size in realloc_head list */
>>> -	list_for_each_entry(dev_res, head, list)
>>> +	list_for_each_entry_safe(dev_res, tmp_res, head, list) {
>>>  		dev_res->res->end += get_res_add_size(realloc_head,
>>>  							dev_res->res);
>>>  
>>> +		if (!(dev_res->res->flags & IORESOURCE_STARTALIGN))
>>> +			continue;
>>> +
>>> +		add_align = get_res_add_align(realloc_head, dev_res->res);
>>> +
>>> +		if (add_align > dev_res->res->start) {
>>> +			dev_res->res->start = add_align;
>>> +			dev_res->res->end = add_align +
>>> +				            resource_size(dev_res->res);
>>> +
>>> +			list_for_each_entry(dev_res2, head, list) {
>>> +				align = pci_resource_alignment(dev_res2->dev,
>>> +							       dev_res2->res);
>>> +				if (add_align > align)
>>> +					list_move_tail(&dev_res->list,
>>> +						       &dev_res2->list);
>>> +			}
>>> +               }
>>> +
>>> +	}
>>> +
>>>  	/* Try updated head list with add_size added */
>>>  	assign_requested_resources_sorted(head, &local_fail_head);
>>>  
>>> @@ -930,6 +974,8 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
>>>  	struct resource *b_res = find_free_bus_resource(bus,
>>>  					mask | IORESOURCE_PREFETCH, type);
>>>  	resource_size_t children_add_size = 0;
>>> +	resource_size_t children_add_align = 0;
>>> +	resource_size_t add_align = 0;
>>>  
>>>  	if (!b_res)
>>>  		return -ENOSPC;
>>> @@ -954,6 +1000,7 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
>>>  			/* put SRIOV requested res to the optional list */
>>>  			if (realloc_head && i >= PCI_IOV_RESOURCES &&
>>>  					i <= PCI_IOV_RESOURCE_END) {
>>> +				add_align = max(pci_resource_alignment(dev, r), add_align);
>>>  				r->end = r->start - 1;
>>>  				add_to_list(realloc_head, dev, r, r_size, 0/* don't care */);
>>>  				children_add_size += r_size;
>>> @@ -984,8 +1031,11 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
>>>  			if (order > max_order)
>>>  				max_order = order;
>>>  
>>> -			if (realloc_head)
>>> +			if (realloc_head) {
>>>  				children_add_size += get_res_add_size(realloc_head, r);
>>> +				children_add_align = get_res_add_align(realloc_head, r);
>>> +				add_align = max(add_align, children_add_align);
>>> +			}
>>>  		}
>>>  	}
>>>  
>>> @@ -996,7 +1046,7 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
>>>  		add_size = children_add_size;
>>>  	size1 = (!realloc_head || (realloc_head && !add_size)) ? size0 :
>>>  		calculate_memsize(size, min_size, add_size,
>>> -				resource_size(b_res), min_align);
>>> +				resource_size(b_res), max(min_align, add_align));
>>>  	if (!size0 && !size1) {
>>>  		if (b_res->start || b_res->end)
>>>  			dev_info(&bus->self->dev, "disabling bridge window %pR to %pR (unused)\n",
>>> @@ -1008,10 +1058,12 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
>>>  	b_res->end = size0 + min_align - 1;
>>>  	b_res->flags |= IORESOURCE_STARTALIGN;
>>>  	if (size1 > size0 && realloc_head) {
>>> -		add_to_list(realloc_head, bus->self, b_res, size1-size0, min_align);
>>> -		dev_printk(KERN_DEBUG, &bus->self->dev, "bridge window %pR to %pR add_size %llx\n",
>>> -			   b_res, &bus->busn_res,
>>> -			   (unsigned long long)size1-size0);
>>> +		add_to_list(realloc_head, bus->self, b_res, size1-size0,
>>> +				max(min_align, add_align));
>>> +		dev_printk(KERN_DEBUG, &bus->self->dev, "bridge window "
>>> +				 "%pR to %pR add_size %llx add_align %llx\n", b_res,
>>> +				 &bus->busn_res, (unsigned long long)size1-size0,
>>> +				 max(min_align, add_align));
>>
>>Factor out this "max(min_align, add_align)" thing so we don't have to
>>change these lines.  Bonus points if you can also factor it out of the
>>calculate_memsize() call above.  That one is a pretty complicated ternary
>>expression that should probably be turned into an "if" instead anyway.
>>
>
>Ok, I get your point. Let me make it more easy to read.
>
>>>  	}
>>>  	return 0;
>>>  }
>>> -- 
>>> 1.7.9.5
>>> 
>
>-- 
>Richard Yang
>Help you, Help me

-- 
Richard Yang
Help you, Help me