On Wed, Sep 27, 2017 at 04:52:31PM +1000, Alexey Kardashevskiy wrote:
> In order to make generic IOV code work, the physical function IOV BAR
> should start from offset of the first VF. Since M64 segments share
> PE number space across PHB, and some PEs may be in use at the time
> when IOV is enabled, the existing code shifts the IOV BAR to the index
> of the first PE/VF. This creates a hole in IOMEM space which can be
> potentially taken by some other device.
> 
> This reserves a temporary hole on a parent and releases it when IOV is
> disabled; the temporary resources are stored in pci_dn to avoid
> kmalloc/free.
> 
> Cc: linux-...@vger.kernel.org
> Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
> Cc: Bjorn Helgaas <bhelg...@google.com>
> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>

Looks good to me.

Acked-by: Bjorn Helgaas <bhelg...@google.com>

I assume this will be merged via the powerpc branch.

> ---
> 
> I assume this goes to powerpc next branch but before this I'd like to
> get Bjorn's opinion as he continously commented on this bit.
> 
> This is the diff in /proc/iomem:
> 
> @@ -11,6 +11,7 @@
>          200800000000-200bffffffff : 0000:04:00.0
>  210000000000-21fdffffffff : /pciex@3fffe40100000
>    210000000000-21fdfff0ffff : PCI Bus 0001:01
> +    210000000000-210009ffffff : pnv_iov_reserved
>      21000a000000-2101ffffffff : 0001:01:00.0
>        21000a000000-21000bffffff : 0001:01:00.2
>          21000a000000-21000bffffff : mlx5_core
> 
> ---
> Changes:
> v2:
> * changed order - now devm_release_resource() is called before
> pci_update_resource(). Strangely the opposite did not produce a warning
> but still
> ---
>  arch/powerpc/include/asm/pci-bridge.h     |  1 +
>  arch/powerpc/platforms/powernv/pci-ioda.c | 24 +++++++++++++++++++++---
>  2 files changed, 22 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/pci-bridge.h 
> b/arch/powerpc/include/asm/pci-bridge.h
> index 0b8aa1fe2d5f..62ed83db04ae 100644
> --- a/arch/powerpc/include/asm/pci-bridge.h
> +++ b/arch/powerpc/include/asm/pci-bridge.h
> @@ -218,6 +218,7 @@ struct pci_dn {
>  #endif
>       struct list_head child_list;
>       struct list_head list;
> +     struct resource holes[PCI_SRIOV_NUM_BARS];
>  };
>  
>  /* Get the pointer to a device_node's pci_dn */
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c 
> b/arch/powerpc/platforms/powernv/pci-ioda.c
> index 57f9e55f4352..d66a758b8efb 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -1002,9 +1002,12 @@ static int pnv_pci_vf_resource_shift(struct pci_dev 
> *dev, int offset)
>       }
>  
>       /*
> -      * After doing so, there would be a "hole" in the /proc/iomem when
> -      * offset is a positive value. It looks like the device return some
> -      * mmio back to the system, which actually no one could use it.
> +      * Since M64 BAR shares segments among all possible 256 PEs,
> +      * we have to shift the beginning of PF IOV BAR to make it start from
> +      * the segment which belongs to the PE number assigned to the first VF.
> +      * This creates a "hole" in the /proc/iomem which could be used for
> +      * allocating other resources so we reserve this area below and
> +      * release when IOV is released.
>        */
>       for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
>               res = &dev->resource[i + PCI_IOV_RESOURCES];
> @@ -1018,7 +1021,22 @@ static int pnv_pci_vf_resource_shift(struct pci_dev 
> *dev, int offset)
>               dev_info(&dev->dev, "VF BAR%d: %pR shifted to %pR (%sabling %d 
> VFs shifted by %d)\n",
>                        i, &res2, res, (offset > 0) ? "En" : "Dis",
>                        num_vfs, offset);
> +
> +             if (offset < 0) {
> +                     devm_release_resource(&dev->dev, &pdn->holes[i]);
> +                     memset(&pdn->holes[i], 0, sizeof(pdn->holes[i]));
> +             }
> +
>               pci_update_resource(dev, i + PCI_IOV_RESOURCES);
> +
> +             if (offset > 0) {
> +                     pdn->holes[i].start = res2.start;
> +                     pdn->holes[i].end = res2.start + size * offset - 1;
> +                     pdn->holes[i].flags = IORESOURCE_BUS;
> +                     pdn->holes[i].name = "pnv_iov_reserved";
> +                     devm_request_resource(&dev->dev, res->parent,
> +                                     &pdn->holes[i]);
> +             }
>       }
>       return 0;
>  }
> -- 
> 2.11.0
> 

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