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SubjectRe: [RFC PATCH v4 1/7] PCI: Add a new option for resource_alignment to reassign alignment
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On 03/07/2016 06:48 PM, Yongji Xie wrote:
> When using resource_alignment kernel parameter, the current
> implement reassigns the alignment by changing resources' size
> which can potentially break some drivers.

How can this possibly break any driver?... It rounds up, not down, what do
I miss here?

>
> So this patch adds a new option "noresize" for the parameter
> to solve this problem.
>
> Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com>
> ---
> Documentation/kernel-parameters.txt | 5 ++++-
> drivers/pci/pci.c | 36 +++++++++++++++++++++++++----------
> 2 files changed, 30 insertions(+), 11 deletions(-)
>
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index 9a53c92..d8b29ab 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -2912,13 +2912,16 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
> window. The default value is 64 megabytes.
> resource_alignment=
> Format:
> - [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
> + [<order of align>@][<domain>:]<bus>:<slot>.<func>
> + [:noresize][; ...]
> Specifies alignment and device to reassign
> aligned memory resources.
> If <order of align> is not specified,
> PAGE_SIZE is used as alignment.
> PCI-PCI bridge can be specified, if resource
> windows need to be expanded.
> + noresize: Don't change the resources' sizes when
> + reassigning alignment.
> ecrc= Enable/disable PCIe ECRC (transaction layer
> end-to-end CRC checking).
> bios: Use BIOS/firmware settings. This is the
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 602eb42..760cce5 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4598,7 +4598,8 @@ static DEFINE_SPINLOCK(resource_alignment_lock);
> * RETURNS: Resource alignment if it is specified.
> * Zero if it is not specified.
> */
> -static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev)
> +static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
> + bool *resize)
> {
> int seg, bus, slot, func, align_order, count;
> resource_size_t align = 0;
> @@ -4626,6 +4627,11 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev)
> }
> }
> p += count;
> + if (!strncmp(p, ":noresize", 9)) {
> + *resize = false;
> + p += 9;
> + } else
> + *resize = true;
> if (seg == pci_domain_nr(dev->bus) &&
> bus == dev->bus->number &&
> slot == PCI_SLOT(dev->devfn) &&
> @@ -4658,11 +4664,12 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
> {
> int i;
> struct resource *r;
> + bool resize;
> resource_size_t align, size;
> u16 command;
>
> /* check if specified PCI is target device to reassign */
> - align = pci_specified_resource_alignment(dev);
> + align = pci_specified_resource_alignment(dev, &resize);

A compiler should have warned here about passing a pointer to unitialized
@resize.


> if (!align)
> return;
>
> @@ -4684,15 +4691,24 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
> if (!(r->flags & IORESOURCE_MEM))
> continue;
> size = resource_size(r);
> - if (size < align) {
> - size = align;
> - dev_info(&dev->dev,
> - "Rounding up size of resource #%d to %#llx.\n",
> - i, (unsigned long long)size);
> + if (resize) {
> + if (size < align) {
> + size = align;
> + dev_info(&dev->dev,
> + "Rounding up size of resource #%d to %#llx.\n",
> + i, (unsigned long long)size);
> + }
> + r->flags |= IORESOURCE_UNSET;
> + r->end = size - 1;
> + r->start = 0;
> + } else {
> + if (size > align)
> + align = size;
> + r->flags &= ~IORESOURCE_SIZEALIGN;
> + r->flags |= IORESOURCE_STARTALIGN | IORESOURCE_UNSET;
> + r->start = align;
> + r->end = r->start + size - 1;
> }
> - r->flags |= IORESOURCE_UNSET;
> - r->end = size - 1;
> - r->start = 0;
> }
> /* Need to disable bridge's resource window,
> * to enable the kernel to reassign new resource
>


--
Alexey

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