Re: Support huge alignment in pbus_size_mem()

[Yinghai Lu <yinghai@kernel.org>]

On Mon, Feb 17, 2014 at 11:28 AM, Yinghai Lu <yinghai@kernel.org> wrote:
> On Sun, Feb 16, 2014 at 8:50 PM, Guo Chao <yan@linux.vnet.ibm.com> wrote:
>> pbus_size_mem() limits resource alignment within 2G. We want to extend
>> this limit to support a 16G BAR. I found similar effort was tried before:
>>
>>         https://lkml.org/lkml/2012/6/21/411
>>
>> What's the result? Does anyone come up with an adaptive algorithm?
>
> I suggest following changes:
>
> From: Nikhil P Rao <nikhil.rao@intel.com>
> Subject: [PATCH] PCI: Fix bus align checking to support more than 2G
>
> current 2G is out of date.
>
> -v3: We only need to extend that when 64bit mmio is supported.
>      So extract mmio64 mask checking, and still keep old 2G checking
>      for other path.  --- Yinghai
>
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
>
> ---
>  drivers/pci/setup-bus.c |   42 ++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 38 insertions(+), 4 deletions(-)
>
> 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
> @@ -921,7 +921,7 @@ static int pbus_size_mem(struct pci_bus
>  {
>      struct pci_dev *dev;
>      resource_size_t min_align, align, size, size0, size1;
> -    resource_size_t aligns[12];    /* Alignments from 1Mb to 2Gb */
> +    resource_size_t aligns[44];    /* Alignments from 1Mb to 2^63 */
>      int order, max_order;
>      struct resource *b_res = find_free_bus_resource(bus, type);
>      unsigned int mem64_mask = 0;
> @@ -937,6 +937,40 @@ static int pbus_size_mem(struct pci_bus
>      mem64_mask = b_res->flags & IORESOURCE_MEM_64;
>      b_res->flags &= ~IORESOURCE_MEM_64;
>
> +    /* kernel does not support 64bit */
> +    if (sizeof(resource_size_t) == 4)
> +        mem64_mask &=  ~IORESOURCE_MEM_64;
> +
> +    if (!(mem64_mask & IORESOURCE_MEM_64))
> +        goto mem64_mask_check_done;
> +
> +    /* check if mem64 support is supported and needed at first */
> +    list_for_each_entry(dev, &bus->devices, bus_list) {
> +        int i;
> +
> +        for (i = 0; i < PCI_NUM_RESOURCES; i++) {
> +            struct resource *r = &dev->resource[i];
> +            resource_size_t r_size;
> +
> +            if (r->parent || (r->flags & mask) != type)
> +                continue;
> +            r_size = resource_size(r);
> +#ifdef CONFIG_PCI_IOV
> +            /* put SRIOV requested res to the optional list */
> +            if (realloc_head && i >= PCI_IOV_RESOURCES &&
> +                    i <= PCI_IOV_RESOURCE_END)
> +                continue;
> +#endif
> +            mem64_mask &= r->flags & IORESOURCE_MEM_64;
> +
> +            if (!(mem64_mask & IORESOURCE_MEM_64))
> +                goto mem64_mask_check_done;
> +
> +        }
> +    }
> +
> +mem64_mask_check_done:
> +
>      list_for_each_entry(dev, &bus->devices, bus_list) {
>          int i;
>
> @@ -959,8 +993,9 @@ static int pbus_size_mem(struct pci_bus
>  #endif
>              /* For bridges size != alignment */
>              align = pci_resource_alignment(dev, r);
> -            order = __ffs(align) - 20;
> -            if (order > 11) {
> +            order = __ffs64(align) - 20;
> +            if (order > ARRAY_SIZE(aligns) ||
> +                (!(mem64_mask & IORESOURCE_MEM_64) && order > 11) ) {

...
> For 64bit systems, we want to ensure that the align < 1^63, so shouldn't
> order be checked against 43, instead of ARRAY_SIZE(aligns) ?

yes, should change to 43.

Thanks

Yinghai