On 2016/6/21 9:57, Bjorn Helgaas wrote:
On Thu, Jun 02, 2016 at 01:46:50PM +0800, 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. For example, the driver
uses the size to locate some register whose length is related
to the size.
This patch adds a new option "noresize" for the parameter to
solve this problem.
Why do we ever want to change the resource's size? I understand that
you want to change the resource's *alignment*, and that part makes
sense. But why change the *size*? Changing the resource size doesn't
change the hardware BAR size; it just means the struct resource will
describe a region larger than what the BAR actually claims. That
unnecessarily wastes space after the BAR.
This was a problem with the code even before your patch; I'm
suggesting that if you have a way to change the alignment without
changing the resource size, maybe we should do that all the time.
Then you wouldn't need to add the "noresize" option.
Yes, changing resource's size seems not a good idea. But
would it break some existing systems which are using this
kernel parameter if we remove the "noresize" option and change
the alignment all the time?
Thanks,
Yongji
Signed-off-by: Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx>
---
Documentation/kernel-parameters.txt | 5 ++++-
drivers/pci/pci.c | 35 +++++++++++++++++++++++++----------
2 files changed, 29 insertions(+), 11 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 82b42c9..c4802f5 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2997,13 +2997,16 @@ 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 a259394..3ee13e5 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4748,11 +4748,13 @@ static DEFINE_SPINLOCK(resource_alignment_lock);
/**
* pci_specified_resource_alignment - get resource alignment specified by user.
* @dev: the PCI device to get
+ * @resize: whether or not to change resources' size when reassigning alignment
*
* 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;
@@ -4786,6 +4788,11 @@ 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) &&
@@ -4818,11 +4825,12 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
{
int i;
struct resource *r;
+ bool resize = true;
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);
if (!align)
return;
@@ -4844,15 +4852,22 @@ 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 {
+ r->flags &= ~IORESOURCE_SIZEALIGN;
+ r->flags |= IORESOURCE_STARTALIGN | IORESOURCE_UNSET;
+ r->start = max(align, size);
+ 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
--
1.7.9.5
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