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Message-Id: <20071028101724.e56da3ce.rdunlap@xenotime.net>
Date: Sun, 28 Oct 2007 10:17:24 -0700
From: Randy Dunlap <rdunlap@...otime.net>
To: "Barak Fargoun" <barak@...cleus.com>
Cc: <linux-kernel@...r.kernel.org>,
<linux-pci@...ey.karlin.mff.cuni.cz>, <gregkh@...e.de>
Subject: Re: [PATCH] Align PCI memory regions to page size (4K)
On Sun, 28 Oct 2007 11:00:38 -0400 Barak Fargoun wrote:
> Add a boot parameter ('pci-mem-align') which forces PCI memory regions
> to be aligned to 4K.
>
>
>
> This is very useful when developing an hypervisor, since in case we want
> to let native domains direct access to specific hardware, we don't want
> PCI devices to share their memory region page with other devices. In Xen
> for example, PCI devices mmio resources are mapped by remapping complete
> pages (by Intel VT-d & the Neocleus pass-through patch for Xen).
>
Hi,
This patch is oddly double-spaced and space-stuffed (spaces instead
of tabs). Likely a mail client doing this. It's usually a
good idea to send patches to yourself to make sure that they will
apply cleanly with 'patch' before unloading them on someone else.
>
> Signed-off-by: Barak Fargoun (barak@...cleus.com)
>
> ---
>
> Kernel version: 2.6.18
>
> ---
>
> diff -r 840b9df48b6a drivers/pci/bus.c
>
> --- a/drivers/pci/bus.c Tue Aug 07 09:37:41 2007 +0100
>
> +++ b/drivers/pci/bus.c Sun Oct 28 08:40:52 2007 -0400
>
> @@ -16,6 +16,8 @@
>
> #include <linux/init.h>
>
>
>
> #include "pci.h"
>
> +
>
> +extern int pci_mem_align;
>
>
>
> /**
>
> * pci_bus_alloc_resource - allocate a resource from a parent bus
>
> @@ -43,6 +45,15 @@ pci_bus_alloc_resource(struct pci_bus *b
>
> int i, ret = -ENOMEM;
>
>
>
> type_mask |= IORESOURCE_IO | IORESOURCE_MEM;
>
> +
>
> + /* if the boot parameter 'pci-mem-align' was specified,
> then we need to
>
> + align the memory addresses, at page size
> alignment */
>
> + if (pci_mem_align)
>
> + {
>
> + /* we change only alignments which are
> smaller than page size */
>
> + if (align < (PAGE_SIZE-1))
>
> + align = PAGE_SIZE - 1;
>
> + }
>
>
>
> for (i = 0; i < PCI_BUS_NUM_RESOURCES; i++) {
>
> struct resource *r = bus->resource[i];
>
> diff -r 840b9df48b6a drivers/pci/quirks.c
>
> --- a/drivers/pci/quirks.c Tue Aug 07 09:37:41 2007 +0100
>
> +++ b/drivers/pci/quirks.c Sun Oct 28 08:40:52 2007 -0400
>
> @@ -22,6 +22,54 @@
>
> #include <linux/delay.h>
>
> #include <linux/acpi.h>
>
> #include "pci.h"
>
> +
>
> +/* a global flag, which signals if we should align PCI mem windows to
> 4K */
>
> +int pci_mem_align = 0;
>
> +
>
> +/* this function is called, if the 'pci-mem-align' was specified as a
> boot
>
> + parameter. Used to force the kernel to
> align PCI mem windows to 4k */
>
> +static int __init set_pci_mem_align(char *str)
>
> +{
>
> + pci_mem_align = 1;
>
> + return 1;
>
> +}
>
> +__setup("pci-mem-align", set_pci_mem_align);
>
> +
>
> +/*
>
> + This quirk function enables us to force all memory
> resources which are
>
> + assigned to PCI devices, to be aligned at
> a page size. This
>
> + fetaurs helps us in xen when running
> native domains
>
> +*/
>
> +static void __devinit quirk_xen_align_mem_resources(struct pci_dev
> *dev)
>
> +{
>
> + int i;
>
> + struct resource *r;
>
> +
>
> + /* if the boot parameter 'pci-mem-align' wasn't specified,
> then no need
>
> + to align the memory addresses */
>
> + if (pci_mem_align == 0)
>
> + return;
>
> +
>
> + for (i=0; i < DEVICE_COUNT_RESOURCE; ++i) {
>
> + r = &dev->resource[i];
>
> +
>
> + if (r == NULL)
>
> + continue;
>
> +
>
> + /* we need to adjust only memory resources
> */
>
> + if (r->flags & IORESOURCE_MEM) {
>
> + /* align the start address
> in page size alignment alignment (round up) */
>
> + resource_size_t old_start
> = r->start;
>
> + r->start = (r->start +
> (PAGE_SIZE-1)) & (~(PAGE_SIZE-1));
>
> +
>
> + /* update the end address,
> so that the region size will not be
>
> + affected
> */
>
> + r->end = r->end -
> (old_start - r->start);
>
> + }
>
> + }
>
> +}
>
> +DECLARE_PCI_FIXUP_HEADER(PCI_ANY_ID, PCI_ANY_ID,
> quirk_xen_align_mem_resources);
>
> +
>
>
>
> /* The Mellanox Tavor device gives false positive parity errors
>
> * Mark this device with a broken_parity_status, to allow
>
>
>
>
---
~Randy
-
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