Re: [PATCH] PCI: Don't let mmio fallback to must-only, if ioportfails with must+optional

[Bjorn Helgaas]

On Thu, May 23, 2013 at 11:11 AM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
> BenH reported that there is some assign unassigned resource problem
> in powerpc.
>
> It turns out after
> | commit 0c5be0cb0edfe3b5c4b62eac68aa2aa15ec681af
> | Date:   Thu Feb 23 19:23:29 2012 -0800
> |
> |    PCI: Retry on IORESOURCE_IO type allocations
>
> even the root bus does not have io port range, it will keep retrying
> to realloc with mmio.
>
> Current retry logic is : try with must+optional at first, and if
> it fails with any ioport or mmio, it will try must then try to extend
> must with optional.
> That will fail as mmio-non-pref and mmio-pref for bridge will
> be next to each other. So we have no chance to extend mmio-non-pref.
>
> We can check fail type and only fall back for io port only, that will
> keep mmio type still have must+optional.
>
> This will be become more often when we have x86 8 sockets or 32 sockets
> system, and those system will have one root bus per socket.
> They will have some root buses do not have ioport range.
>
> -v2: need to remove assigned entries from optional list too.
>
> Reported-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> Tested-by: Gavin Shan <shangw@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
>
> ---
>  drivers/pci/setup-bus.c |   23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
>
> Index: linux-2.6/drivers/pci/setup-bus.c
> ===================================================================
> --- linux-2.6.orig/drivers/pci/setup-bus.c
> +++ linux-2.6/drivers/pci/setup-bus.c
> @@ -317,6 +317,10 @@ static void __assign_resources_sorted(st
>         LIST_HEAD(local_fail_head);
>         struct pci_dev_resource *save_res;
>         struct pci_dev_resource *dev_res;
> +       unsigned long fail_type = 0;
> +       struct pci_dev_resource *fail_res;
> +       unsigned long type_mask = IORESOURCE_IO | IORESOURCE_MEM |
> +                                 IORESOURCE_PREFETCH;
>
>         /* Check if optional add_size is there */
>         if (!realloc_head || list_empty(realloc_head))
> @@ -348,6 +352,25 @@ static void __assign_resources_sorted(st
>                 return;
>         }
>
> +       /* check failed type */
> +       list_for_each_entry(fail_res, &local_fail_head, list)
> +               fail_type |= fail_res->flags & type_mask;
> +       /* only io port fails */
> +       if ((fail_type & type_mask) == IORESOURCE_IO) {
> +               struct pci_dev_resource *tmp_res;
> +
> +               /* remove assigned non ioport from head list etc */
> +               list_for_each_entry_safe(dev_res, tmp_res, head, list)
> +                       if (dev_res->res->parent &&
> +                           !(dev_res->res->flags & IORESOURCE_IO)) {
> +                               /* remove it from realloc_head list */
> +                               remove_from_list(realloc_head, dev_res->res);
> +                               remove_from_list(&save_head, dev_res->res);
> +                               list_del(&dev_res->list);
> +                               kfree(dev_res);
> +                       }
> +       }

The problem we're trying to solve is that when allocation for type X
fails, we retry allocation for type Y.

This patch handles IO specially.  I think it basically says, "if we
only have IO allocation failures, don't retry MEM allocation."  But a
clean strategy would also avoid retrying IO allocation if we only had
MEM allocation failures.

Bjorn

>         free_list(&local_fail_head);
>         /* Release assigned resource */
>         list_for_each_entry(dev_res, head, list)
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