Subject: Re: [PATCH v12 10/21] PCI: Consider additional PF's IOV BAR alignment in sizing and assigning

From: Bjorn Helgaas <[email-masked]>
Date: Tue, 24 Feb 2015 02:41:52 -0600

On Tue, Feb 24, 2015 at 02:34:06AM -0600, Bjorn Helgaas wrote:
> From: Wei Yang <[email-masked]>
> 
> When sizing and assigning resources, we divide the resources into two
> lists: the requested list and the additional list.  We don't consider the
> alignment of additional VF(n) BAR space.
> 
> This is reasonable because the alignment required for the VF(n) BAR space
> is the size of an individual VF BAR, not the size of the space for *all*
> VFs.  But some platforms, e.g., PowerNV, require additional alignment.
> 
> Consider the additional IOV BAR alignment when sizing and assigning
> resources.  When there is not enough system MMIO space, the PF's IOV BAR
> alignment will not contribute to the bridge.  When there is enough system
> MMIO space, the additional alignment will contribute to the bridge.

I don't understand the ""when there is not enough system MMIO space" part.
How do we tell if there's enough MMIO space?

> Also, take advantage of pci_dev_resource::min_align to store this
> additional alignment.

This comment doesn't seem to make sense; this patch doesn't save anything
in min_align.

Another question below...

> [bhelgaas: changelog, printk cast]
> Signed-off-by: Wei Yang <[email-masked]>
> Signed-off-by: Bjorn Helgaas <[email-masked]>
> ---
>  drivers/pci/setup-bus.c |   83 ++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 70 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index e3e17f3c0f0f..affbceae560f 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -99,8 +99,8 @@ static void remove_from_list(struct list_head *head,
>  	}
>  }
>  
> -static resource_size_t get_res_add_size(struct list_head *head,
> -					struct resource *res)
> +static struct pci_dev_resource *res_to_dev_res(struct list_head *head,
> +					       struct resource *res)
>  {
>  	struct pci_dev_resource *dev_res;
>  
> @@ -109,17 +109,37 @@ static resource_size_t get_res_add_size(struct list_head *head,
>  			int idx = res - &dev_res->dev->resource[0];
>  
>  			dev_printk(KERN_DEBUG, &dev_res->dev->dev,
> -				 "res[%d]=%pR get_res_add_size add_size %llx\n",
> +				 "res[%d]=%pR res_to_dev_res add_size %llx min_align %llx\n",
>  				 idx, dev_res->res,
> -				 (unsigned long long)dev_res->add_size);
> +				 (unsigned long long)dev_res->add_size,
> +				 (unsigned long long)dev_res->min_align);
>  
> -			return dev_res->add_size;
> +			return dev_res;
>  		}
>  	}
>  
> -	return 0;
> +	return NULL;
> +}
> +
> +static resource_size_t get_res_add_size(struct list_head *head,
> +					struct resource *res)
> +{
> +	struct pci_dev_resource *dev_res;
> +
> +	dev_res = res_to_dev_res(head, res);
> +	return dev_res ? dev_res->add_size : 0;
> +}
> +
> +static resource_size_t get_res_add_align(struct list_head *head,
> +					 struct resource *res)
> +{
> +	struct pci_dev_resource *dev_res;
> +
> +	dev_res = res_to_dev_res(head, res);
> +	return dev_res ? dev_res->min_align : 0;
>  }
>  
> +
>  /* Sort resources by alignment */
>  static void pdev_sort_resources(struct pci_dev *dev, struct list_head *head)
>  {
> @@ -368,8 +388,9 @@ 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 +405,38 @@ 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);
>  
> +		/*
> +		 * There are two kinds of additional resources in the list:
> +		 * 1. bridge resource  -- IORESOURCE_STARTALIGN
> +		 * 2. SR-IOV resource   -- IORESOURCE_SIZEALIGN
> +		 * Here just fix the additional alignment for bridge
> +		 */
> +		if (!(dev_res->res->flags & IORESOURCE_STARTALIGN))
> +			continue;
> +
> +		add_align = get_res_add_align(realloc_head, dev_res->res);
> +
> +		/* Reorder the list by their alignment */

Why do we need to reorder the list by alignment?

> +		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);
>  
> @@ -962,6 +1011,8 @@ 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;
> @@ -986,6 +1037,7 @@ 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;
> @@ -1016,19 +1068,23 @@ 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);
> +			}
>  		}
>  	}
>  
>  	min_align = calculate_mem_align(aligns, max_order);
>  	min_align = max(min_align, window_alignment(bus, b_res->flags));
>  	size0 = calculate_memsize(size, min_size, 0, resource_size(b_res), min_align);
> +	add_align = max(min_align, add_align);
>  	if (children_add_size > add_size)
>  		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), 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",
> @@ -1040,10 +1096,11 @@ 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",
> +		add_to_list(realloc_head, bus->self, b_res, size1-size0, 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);
> +			   (unsigned long long) (size1 - size0),
> +			   (unsigned long long) add_align);
>  	}
>  	return 0;
>  }
>