Subject: Re: [PATCH V7 02/17] PCI/IOV: Get VF BAR size from hardware directly when platform needs

From: Bjorn Helgaas <[email-masked]>
Date: Tue, 19 Aug 2014 15:44:59 -0600

On Thu, Jul 24, 2014 at 02:22:12PM +0800, Wei Yang wrote:
> Current implementation calculates VF BAR size from dividing the total size of
> IOV BAR by total VF number. It won't work on PowerNV platform because we're
> going to expand IOV BAR size for finely alignment.
> 
> The patch enforces getting IOV BAR size from hardware and then calculate
> the VF BAR size based on that when platform wants so.
> 
> Signed-off-by: Wei Yang <[email-masked]>
> ---
>  drivers/pci/iov.c      |   28 ++++++++++++++++++++++++----
>  include/linux/ioport.h |    1 +
>  2 files changed, 25 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 7566238..ef1c546 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -55,6 +55,9 @@ static int virtfn_add(struct pci_dev *dev, int id, int reset)
>  	struct resource *res;
>  	struct pci_sriov *iov = dev->sriov;
>  	struct pci_bus *bus;
> +	struct resource tmp;
> +	enum pci_bar_type type;
> +	int reg;
>  
>  	mutex_lock(&iov->dev->sriov->lock);
>  	bus = virtfn_add_bus(dev->bus, pci_iov_virtfn_bus(dev, id));
> @@ -80,12 +83,29 @@ static int virtfn_add(struct pci_dev *dev, int id, int reset)
>  			continue;
>  		virtfn->resource[i].name = pci_name(virtfn);
>  		virtfn->resource[i].flags = res->flags;
> -		size = resource_size(res);
> -		do_div(size, iov->total_VFs);
> +		/* When res has IORESOURCE_ARCH, retrieve the IOV BAR size
> +		 * from hardware directly.
> +		 */
> +		if (res->flags & IORESOURCE_ARCH) {
> +			reg = pci_iov_resource_bar(dev, i + PCI_IOV_RESOURCES, &type);
> +			__pci_read_base(dev, type, &tmp, reg);
> +			size = resource_size(&tmp);
> +			/* When __pci_read_base fails, flags is set to 0.
> +			 * In this case, reset size to 0, which means the VF
> +			 * will not be enabled.
> +			 */
> +			if (!tmp.flags)
> +				size = 0;

I don't like the IORESOURCE_ARCH flag because it really doesn't have any
specific meaning.  You're using it to enable some arch-specific code here
for this specific case.  But there are any number of other places that
could do something similar, and there's no way to coordinate them all.

I'd rather have some sort of pcibios_*() hook here where powerpc could
override the default implementation.

> +		} else {
> +			size = resource_size(res);
> +			do_div(size, iov->total_VFs);
> +		}
>  		virtfn->resource[i].start = res->start + size * id;
>  		virtfn->resource[i].end = virtfn->resource[i].start + size - 1;
> -		rc = request_resource(res, &virtfn->resource[i]);
> -		BUG_ON(rc);
> +		if (resource_size(&virtfn->resource[i])) {
> +			rc = request_resource(res, &virtfn->resource[i]);
> +			BUG_ON(rc);
> +		}
>  	}
>  
>  	if (reset)
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index 5e3a906..de8b57c 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -48,6 +48,7 @@ struct resource {
>  #define IORESOURCE_MEM_64	0x00100000
>  #define IORESOURCE_WINDOW	0x00200000	/* forwarded by bridge */
>  #define IORESOURCE_MUXED	0x00400000	/* Resource is software muxed */
> +#define IORESOURCE_ARCH		0x00800000	/* Resource arch tagged */
>
>  #define IORESOURCE_EXCLUSIVE	0x08000000	/* Userland may not map this resource */
>  #define IORESOURCE_DISABLED	0x10000000
> -- 
> 1.7.9.5
>