linux-kernel - Re: [PATCH v3] PCI: Equalize hotplug memory and io for non/occupied slots

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Message-ID: <20180926222322.GL28024@bhelgaas-glaptop.roam.corp.google.com>
Date:   Wed, 26 Sep 2018 17:23:22 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Jon Derrick <jonathan.derrick@...el.com>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sinan Kaya <okaya@...nel.org>, Christoph Hellwig <hch@....de>,
        Keith Busch <keith.busch@...el.com>,
        Matthew Wilcox <willy@...radead.org>,
        Logan Gunthorpe <logang@...tatee.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: [PATCH v3] PCI: Equalize hotplug memory and io for non/occupied
 slots

On Tue, Sep 25, 2018 at 12:39:06PM -0600, Jon Derrick wrote:
> Currently, a hotplug bridge will be given hpmemsize additional memory
> and hpiosize additional io if available, in order to satisfy any future
> hotplug allocation requirements.
> 
> These calculations don't consider the current memory/io size of the
> hotplug bridge/slot, so hotplug bridges/slots which have downstream
> devices will be allocated their current allocation in addition to the
> hpmemsize value.
> 
> This makes for possibly undesirable results with a mix of unoccupied and
> occupied slots (ex, with hpmemsize=2M):
> 
> 02:03.0 PCI bridge: <-- Occupied
> 	Memory behind bridge: d6200000-d64fffff [size=3M]
> 02:04.0 PCI bridge: <-- Unoccupied
> 	Memory behind bridge: d6500000-d66fffff [size=2M]
> 
> This change considers the current allocation size when using the
> hpmemsize/hpiosize parameters to make the reservations predictable for
> the mix of unoccupied and occupied slots:
> 
> 02:03.0 PCI bridge: <-- Occupied
> 	Memory behind bridge: d6200000-d63fffff [size=2M]
> 02:04.0 PCI bridge: <-- Unoccupied
> 	Memory behind bridge: d6400000-d65fffff [size=2M]
> 
> Signed-off-by: Jon Derrick <jonathan.derrick@...el.com>

Applied to pci/hotplug for v4.20, thanks!

> ---
> v2->v3: Made the IO and mem size calculations nearly equivalent
> 
>  drivers/pci/setup-bus.c | 28 +++++++++++++++-------------
>  1 file changed, 15 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index 79b1824..ed96043 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -811,6 +811,8 @@ static struct resource *find_free_bus_resource(struct pci_bus *bus,
>  static resource_size_t calculate_iosize(resource_size_t size,
>  		resource_size_t min_size,
>  		resource_size_t size1,
> +		resource_size_t add_size,
> +		resource_size_t children_add_size,
>  		resource_size_t old_size,
>  		resource_size_t align)
>  {
> @@ -823,15 +825,18 @@ static resource_size_t calculate_iosize(resource_size_t size,
>  #if defined(CONFIG_ISA) || defined(CONFIG_EISA)
>  	size = (size & 0xff) + ((size & ~0xffUL) << 2);
>  #endif
> -	size = ALIGN(size + size1, align);
> +	size = size + size1;
>  	if (size < old_size)
>  		size = old_size;
> +
> +	size = ALIGN(max(size, add_size) + children_add_size, align);
>  	return size;
>  }
>  
>  static resource_size_t calculate_memsize(resource_size_t size,
>  		resource_size_t min_size,
> -		resource_size_t size1,
> +		resource_size_t add_size,
> +		resource_size_t children_add_size,
>  		resource_size_t old_size,
>  		resource_size_t align)
>  {
> @@ -841,7 +846,8 @@ static resource_size_t calculate_memsize(resource_size_t size,
>  		old_size = 0;
>  	if (size < old_size)
>  		size = old_size;
> -	size = ALIGN(size + size1, align);
> +
> +	size = ALIGN(max(size, add_size) + children_add_size, align);
>  	return size;
>  }
>  
> @@ -930,12 +936,10 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size,
>  		}
>  	}
>  
> -	size0 = calculate_iosize(size, min_size, size1,
> +	size0 = calculate_iosize(size, min_size, size1, 0, 0,
>  			resource_size(b_res), min_align);
> -	if (children_add_size > add_size)
> -		add_size = children_add_size;
> -	size1 = (!realloc_head || (realloc_head && !add_size)) ? size0 :
> -		calculate_iosize(size, min_size, add_size + size1,
> +	size1 = (!realloc_head || (realloc_head && !add_size && !children_add_size)) ? size0 :
> +		calculate_iosize(size, min_size, size1, add_size, children_add_size,
>  			resource_size(b_res), min_align);
>  	if (!size0 && !size1) {
>  		if (b_res->start || b_res->end)
> @@ -1079,12 +1083,10 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
>  
>  	min_align = calculate_mem_align(aligns, max_order);
>  	min_align = max(min_align, window_alignment(bus, b_res->flags));
> -	size0 = calculate_memsize(size, min_size, 0, resource_size(b_res), min_align);
> +	size0 = calculate_memsize(size, min_size, 0, 0, resource_size(b_res), min_align);
>  	add_align = max(min_align, add_align);
> -	if (children_add_size > add_size)
> -		add_size = children_add_size;
> -	size1 = (!realloc_head || (realloc_head && !add_size)) ? size0 :
> -		calculate_memsize(size, min_size, add_size,
> +	size1 = (!realloc_head || (realloc_head && !add_size && !children_add_size)) ? size0 :
> +		calculate_memsize(size, min_size, add_size, children_add_size,
>  				resource_size(b_res), add_align);
>  	if (!size0 && !size1) {
>  		if (b_res->start || b_res->end)
> -- 
> 1.8.3.1
>