On Tue, Sep 13, 2016 at 05:00:33PM +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.
>
> Signed-off-by: Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx>
> ---
> Documentation/kernel-parameters.txt | 9 ++++++---
> drivers/pci/pci.c | 37 +++++++++++++++++++++++++----------
> 2 files changed, 33 insertions(+), 13 deletions(-)
>
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index a4f4d69..d6a340d 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -3023,9 +3023,10 @@ 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>@]pci:<vendor>:<device>\
> - [:<subvendor>:<subdevice>][; ...]
> + [<order of align>@][noresize@][<domain>:]
> + <bus>:<slot>.<func>[; ...]
> + [<order of align>@][noresize@]pci:<vendor>:<device>
> + [:<subvendor>:<subdevice>][; ...]
> Specifies alignment and device to reassign
> aligned memory resources.
> If <order of align> is not specified,
> @@ -3036,6 +3037,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
> instances of a device, the PCI vendor,
> device, subvendor, and subdevice may be
> specified, e.g., 4096@pci:8086:9c22:103c:198f
> + 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 b8357d7..37f8062 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4946,11 +4946,13 @@ 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;
> unsigned short vendor, device, subsystem_vendor, subsystem_device;
> @@ -4974,6 +4976,13 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev)
> } else {
> align_order = -1;
> }
> +
> + if (!strncmp(p, "noresize@", 9)) {
> + *resize = false;
> + p += 9;
> + } else
> + *resize = true;
> +
> if (strncmp(p, "pci:", 4) == 0) {
> /* PCI vendor/device (subvendor/subdevice) ids are specified */
> p += 4;
> @@ -5045,6 +5054,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
> {
> int i;
> struct resource *r;
> + bool resize = true;
> resource_size_t align, size;
> u16 command;
>
> @@ -5058,7 +5068,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
> return;
>
> /* 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;
>
> @@ -5086,15 +5096,22 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
> }
>
> 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;
Why do you want to keep this code that changes the size of the resource?
Can't we just *always* use IORESOURCE_STARTALIGN as below? It seems like
that would potentially fix bugs, as you mention.
I think it'd be better if we didn't change the size, even if the user
didn't specify "noresize@". We wouldn't even need the "noresize@" option
then.
Or is there some reason to keep the resize? If it's just a question of
being afraid to change the existing behavior because of the risk, I'm
willing to take that risk.
> + } 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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