Re: [PATCH v5 3/6] PCI: add functionality for resizing resources v6

[Bjorn Helgaas]

On Fri, Jun 09, 2017 at 10:59:44AM +0200, Christian König wrote:
> From: Christian König <christian.koenig@xxxxxxx>
> 
> This allows device drivers to request resizing their BARs.
> 
> The function only tries to reprogram the windows of the bridge directly above
> the requesting device and only the BAR of the same type (usually mem, 64bit,
> prefetchable). This is done to make sure not to disturb other drivers by
> changing the BARs of their devices.
> 
> If reprogramming the bridge BAR fails the old status is restored and -ENOSPC
> returned to the calling device driver.

Can you include an outline of how drivers should use
pci_resize_resource() here, including disabling decoding, releasing
resource(s), resizing, re-enabling decoding, re-reading
pdev->resource[]?

> v2: rebase on changes in rbar support
> v3: style cleanups, fail if memory decoding is enabled or resources
>     still allocated, resize all unused bridge BARs,
>     drop calling pci_reenable_device
> v4: print resources before releasing them, style cleanups,
>     use pci_rbar_size_to_bytes, use PCI_RES_TYPE_MASK
> v5: use next pointer to simplify loop
> v6: move reassigning resources on error to driver side
> 
> Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> ---
>  drivers/pci/setup-bus.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++
>  drivers/pci/setup-res.c | 58 +++++++++++++++++++++++++++++
>  include/linux/pci.h     |  3 ++
>  3 files changed, 159 insertions(+)
> 
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index 451a9c0..2ea872d 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -1908,6 +1908,104 @@ void pci_assign_unassigned_bridge_resources(struct pci_dev *bridge)
>  }
>  EXPORT_SYMBOL_GPL(pci_assign_unassigned_bridge_resources);
>  
> +int pci_reassign_bridge_resources(struct pci_dev *bridge, unsigned long type)
> +{
> +	struct pci_dev_resource *dev_res;
> +	struct pci_dev *next;
> +	LIST_HEAD(saved);
> +	LIST_HEAD(added);
> +	LIST_HEAD(failed);
> +	unsigned int i;
> +	int ret;
> +
> +	/* Walk to the root hub, releasing bridge BARs when possible */
> +	next = bridge;
> +	do {
> +		bridge = next;
> +		for (i = PCI_BRIDGE_RESOURCES; i < PCI_BRIDGE_RESOURCE_END;
> +		     i++) {
> +			struct resource *res = &bridge->resource[i];
> +
> +			if ((res->flags ^ type) & PCI_RES_TYPE_MASK)
> +				continue;
> +
> +			/* Ignore BARs which are still in use */
> +			if (res->child)
> +				continue;
> +
> +			ret = add_to_list(&saved, bridge, res, 0, 0);
> +			if (ret)
> +				goto cleanup;
> +
> +			dev_info(&bridge->dev, "BAR %d: releasing %pR\n",
> +				 i, res);
> +
> +			if (res->parent)
> +				release_resource(res);
> +			res->start = 0;
> +			res->end = 0;
> +			break;
> +		}
> +		if (i == PCI_BRIDGE_RESOURCE_END)
> +			break;
> +
> +		next = bridge->bus ? bridge->bus->self : NULL;
> +	} while (next);
> +
> +	if (list_empty(&saved))
> +		return -ENOENT;
> +
> +	__pci_bus_size_bridges(bridge->subordinate, &added);
> +	__pci_bridge_assign_resources(bridge, &added, &failed);
> +	BUG_ON(!list_empty(&added));
> +
> +	if (!list_empty(&failed)) {
> +		ret = -ENOSPC;
> +		goto cleanup;
> +	}
> +
> +	list_for_each_entry(dev_res, &saved, list) {
> +		/* Skip the bridge we just assigned resources for. */
> +		if (bridge == dev_res->dev)
> +			continue;
> +
> +		bridge = dev_res->dev;
> +		pci_setup_bridge(bridge->subordinate);
> +	}
> +
> +	free_list(&saved);
> +	return 0;
> +
> +cleanup:
> +	/* restore size and flags */
> +	list_for_each_entry(dev_res, &failed, list) {
> +		struct resource *res = dev_res->res;
> +
> +		res->start = dev_res->start;
> +		res->end = dev_res->end;
> +		res->flags = dev_res->flags;
> +	}
> +	free_list(&failed);
> +
> +	/* Revert to the old configuration */
> +	list_for_each_entry(dev_res, &saved, list) {
> +		struct resource *res = dev_res->res;
> +
> +		bridge = dev_res->dev;
> +		i = res - bridge->resource;
> +
> +		res->start = dev_res->start;
> +		res->end = dev_res->end;
> +		res->flags = dev_res->flags;
> +
> +		pci_claim_resource(bridge, i);
> +		pci_setup_bridge(bridge->subordinate);
> +	}
> +	free_list(&saved);
> +
> +	return ret;
> +}
> +
>  void pci_assign_unassigned_bus_resources(struct pci_bus *bus)
>  {
>  	struct pci_dev *dev;
> diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c
> index 4bc589e..077c515 100644
> --- a/drivers/pci/setup-res.c
> +++ b/drivers/pci/setup-res.c
> @@ -383,6 +383,64 @@ int pci_reassign_resource(struct pci_dev *dev, int resno, resource_size_t addsiz
>  	return 0;
>  }
>  
> +void pci_release_resource(struct pci_dev *dev, int resno)
> +{
> +	struct resource *res = dev->resource + resno;
> +
> +	dev_info(&dev->dev, "BAR %d: releasing %pR\n", resno, res);
> +	release_resource(res);
> +	res->end = resource_size(res) - 1;
> +	res->start = 0;
> +	res->flags |= IORESOURCE_UNSET;
> +}
> +EXPORT_SYMBOL(pci_release_resource);
> +
> +int pci_resize_resource(struct pci_dev *dev, int resno, int size)
> +{
> +	struct resource *res = dev->resource + resno;
> +	int old, ret;
> +	u32 sizes;
> +	u16 cmd;
> +
> +	/* Make sure the resource isn't assigned before resizing it. */
> +	if (!(res->flags & IORESOURCE_UNSET))
> +		return -EBUSY;
> +
> +	pci_read_config_word(dev, PCI_COMMAND, &cmd);
> +	if (cmd & PCI_COMMAND_MEMORY)
> +		return -EBUSY;
> +
> +	sizes = pci_rbar_get_possible_sizes(dev, resno);
> +	if (!sizes)
> +		return -ENOTSUPP;
> +
> +	if (!(sizes & BIT(size)))
> +		return -EINVAL;
> +
> +	old = pci_rbar_get_current_size(dev, resno);
> +	if (old < 0)
> +		return old;
> +
> +	ret = pci_rbar_set_size(dev, resno, size);
> +	if (ret)
> +		return ret;
> +
> +	res->end = res->start + pci_rbar_size_to_bytes(size) - 1;
> +
> +	/* Check if the new config works by trying to assign everything. */
> +	ret = pci_reassign_bridge_resources(dev->bus->self, res->flags);
> +	if (ret)
> +		goto error_resize;
> +
> +	return 0;
> +
> +error_resize:
> +	pci_rbar_set_size(dev, resno, old);
> +	res->end = res->start + pci_rbar_size_to_bytes(old) - 1;
> +	return ret;
> +}
> +EXPORT_SYMBOL(pci_resize_resource);
> +
>  int pci_enable_resources(struct pci_dev *dev, int mask)
>  {
>  	u16 cmd, old_cmd;
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index eb3da1a..2d631ad 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1068,6 +1068,8 @@ void pci_reset_bridge_secondary_bus(struct pci_dev *dev);
>  void pci_update_resource(struct pci_dev *dev, int resno);
>  int __must_check pci_assign_resource(struct pci_dev *dev, int i);
>  int __must_check pci_reassign_resource(struct pci_dev *dev, int i, resource_size_t add_size, resource_size_t align);
> +void pci_release_resource(struct pci_dev *dev, int resno);
> +int __must_check pci_resize_resource(struct pci_dev *dev, int i, int size);
>  int pci_select_bars(struct pci_dev *dev, unsigned long flags);
>  bool pci_device_is_present(struct pci_dev *pdev);
>  void pci_ignore_hotplug(struct pci_dev *dev);
> @@ -1148,6 +1150,7 @@ void pci_assign_unassigned_resources(void);
>  void pci_assign_unassigned_bridge_resources(struct pci_dev *bridge);
>  void pci_assign_unassigned_bus_resources(struct pci_bus *bus);
>  void pci_assign_unassigned_root_bus_resources(struct pci_bus *bus);
> +int pci_reassign_bridge_resources(struct pci_dev *bridge, unsigned long type);
>  void pdev_enable_device(struct pci_dev *);
>  int pci_enable_resources(struct pci_dev *, int mask);
>  void pci_fixup_irqs(u8 (*)(struct pci_dev *, u8 *),
> -- 
> 2.7.4
>