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Message-Id: <201010221616.35260.bjorn.helgaas@hp.com>
Date: Fri, 22 Oct 2010 16:16:34 -0600
From: Bjorn Helgaas <bjorn.helgaas@...com>
To: Ram Pai <linuxram@...ibm.com>
Cc: Jesse Barnes <jbarnes@...tuousgeek.org>, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org, clemens@...isch.de,
Yinghai Lu <yinghai@...nel.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
peter.henriksson@...il.com, ebiederm@...stanetworks.com
Subject: Re: [PATCH 1/1] PCI: ignore failure to preallocate minimal resources to hotplug bridges
On Friday, October 22, 2010 11:16:40 am Ram Pai wrote:
> PCI: ignore failure to preallocate minimal resources to
> hotplug bridges
>
> Linux tries to pre-allocate minimal resources to hotplug
> bridges. This works fine as long as there are enough
> resources to satisfy all other genuine resource
> requirements. However if enough resources are not
> available to satisfy the pre-allocation, the
> resource-allocator reports errors and returns failure.
>
> This patch distinguishes between must-need resources and
> nice-to-have resources. Any failure to allocate
> nice-to-have resources are ignored.
>
> This behavior can be particularly useful to trigger
> automatic reallocation, if the OS discovers genuine
> resource allocation conflicts or genuine unallocated
> BARs caused by not-so-smart allocation behavior of the
> native BIOS.
>
> The motivation for this patch is due a issue reported in
> https://bugzilla.kernel.org/show_bug.cgi?id=15960
No need to justify both margins, the left is enough :-)
Doesn't need to be indented either.
> Signed-off-by: Ram Pai <linuxram@...ibm.com>
>
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index 66cb8f4..3bbc427 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -412,14 +412,14 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size)
> {
> struct pci_dev *dev;
> struct resource *b_res = find_free_bus_resource(bus, IORESOURCE_IO);
> - unsigned long size = 0, size1 = 0, old_size;
> + unsigned long size = 0, size1 = 0, old_size, dev_present=0;
General rule of thumb: when modifying code always follow the
existing style for spacing, indentation, etc. In this case
you would need spaces around the "=".
> if (!b_res)
> return;
>
> list_for_each_entry(dev, &bus->devices, bus_list) {
> int i;
> -
> + dev_present=1;
> for (i = 0; i < PCI_NUM_RESOURCES; i++) {
> struct resource *r = &dev->resource[i];
> unsigned long r_size;
> @@ -460,6 +460,12 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size)
> b_res->start = 4096;
> b_res->end = b_res->start + size - 1;
> b_res->flags |= IORESOURCE_STARTALIGN;
> +
> + /* if no devices are behind this bus, inform
> + * resource-allocater to try hard but not to worry
> + * if allocations fail
> + */
> + b_res->flags |= (!dev_present) ? IORESOURCE_IGNORE_FAIL : 0;
> }
>
> /* Calculate the size of the bus and minimal alignment which
> @@ -470,7 +476,7 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
> struct pci_dev *dev;
> resource_size_t min_align, align, size, old_size;
> resource_size_t aligns[12]; /* Alignments from 1Mb to 2Gb */
> - int order, max_order;
> + int order, max_order, dev_present=0;
> struct resource *b_res = find_free_bus_resource(bus, type);
> unsigned int mem64_mask = 0;
>
> @@ -487,6 +493,7 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
> list_for_each_entry(dev, &bus->devices, bus_list) {
> int i;
>
> + dev_present=1;
> for (i = 0; i < PCI_NUM_RESOURCES; i++) {
> struct resource *r = &dev->resource[i];
> resource_size_t r_size;
> @@ -550,6 +557,13 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
> b_res->end = size + min_align - 1;
> b_res->flags |= IORESOURCE_STARTALIGN;
> b_res->flags |= mem64_mask;
> +
> + /* if no devices are behind this bus, inform
> + * resource-allocater to try hard but not to worry
> + * if allocations fail
> + */
> + b_res->flags |= (!dev_present) ? IORESOURCE_IGNORE_FAIL : 0;
> +
> return 1;
> }
>
> diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c
> index 2aaa131..a8ce953 100644
> --- a/drivers/pci/setup-res.c
> +++ b/drivers/pci/setup-res.c
> @@ -210,7 +210,8 @@ int pci_assign_resource(struct pci_dev *dev, int resno)
> if (!align) {
> dev_info(&dev->dev, "BAR %d: can't assign %pR "
> "(bogus alignment)\n", resno, res);
> - return -EINVAL;
> + ret = -EINVAL;
> + goto out;
> }
>
> bus = dev->bus;
> @@ -225,6 +226,10 @@ int pci_assign_resource(struct pci_dev *dev, int resno)
> }
>
> if (ret) {
> + if (res->flags & IORESOURCE_IGNORE_FAIL) {
You might be able to do something like this:
if (dev->subordinate && list_empty(&dev->subordinate->devices))
and avoid the need for a new flag.
I'm not sure this approach is enough, though. What if we have 4K of
I/O space available, and we have this situation:
bridge A (disabled)
bridge B (disabled)
dev D (needs I/O space)
I think your patch will let us ignore a failure to allocate space for
bridge A. But the real problem is the order: we have to allocate space
for bridge B *first*.
Bjorn
> + ret = 0;
> + goto out;
> + }
> if (res->flags & IORESOURCE_MEM)
> if (res->flags & IORESOURCE_PREFETCH)
> type = "mem pref";
> @@ -239,6 +244,8 @@ int pci_assign_resource(struct pci_dev *dev, int resno)
> resno, type, (unsigned long long) resource_size(res));
> }
>
> +out:
> + res->flags &= ~IORESOURCE_IGNORE_FAIL;
> return ret;
> }
>
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index b227902..941624b 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -49,6 +49,7 @@ struct resource_list {
>
> #define IORESOURCE_SIZEALIGN 0x00040000 /* size indicates alignment */
> #define IORESOURCE_STARTALIGN 0x00080000 /* start field is alignment */
> +#define IORESOURCE_IGNORE_FAIL 0x00800000 /* IGNORE if allocation fail*/
>
> #define IORESOURCE_MEM_64 0x00100000
> #define IORESOURCE_WINDOW 0x00200000 /* forwarded by bridge */
>
--
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