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Date: Thu, 14 Nov 2019 10:56:37 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Nicholas Johnson <nicholas.johnson-opensource@...look.com.au>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>,
"corbet@....net" <corbet@....net>,
"benh@...nel.crashing.org" <benh@...nel.crashing.org>,
"logang@...tatee.com" <logang@...tatee.com>
Subject: Re: [PATCH v3 1/1] PCI: Fix bug resulting in double hpmemsize being
assigned to MMIO window
On Wed, Nov 13, 2019 at 03:25:28PM +0000, Nicholas Johnson wrote:
> Currently, the kernel can sometimes assign the MMIO_PREF window
> additional size into the MMIO window, resulting in extra MMIO additional
> size, despite the MMIO_PREF additional size being assigned successfully
> into the MMIO_PREF window.
>
> This happens if in the first pass, the MMIO_PREF succeeds but the MMIO
> fails. In the next pass, because MMIO_PREF is already assigned, the
> attempt to assign MMIO_PREF returns an error code instead of success
> (nothing more to do, already allocated). Hence, the size which is
> actually allocated, but thought to have failed, is placed in the MMIO
> window.
>
> Example of problem (more context can be found in the bug report URL):
>
> Mainline kernel:
> pci 0000:06:01.0: BAR 14: assigned [mem 0x90100000-0xa00fffff] = 256M
> pci 0000:06:04.0: BAR 14: assigned [mem 0xa0200000-0xb01fffff] = 256M
>
> Patched kernel:
> pci 0000:06:01.0: BAR 14: assigned [mem 0x90100000-0x980fffff] = 128M
> pci 0000:06:04.0: BAR 14: assigned [mem 0x98200000-0xa01fffff] = 128M
>
> This was using pci=realloc,hpmemsize=128M,nocrs - on the same machine
> with the same configuration, with a Ubuntu mainline kernel and a kernel
> patched with this patch.
>
> The bug results in the MMIO_PREF being added to the MMIO window, which
> means doubling if MMIO_PREF size = MMIO size. With a large MMIO_PREF,
> the MMIO window will likely fail to be assigned altogether due to lack
> of 32-bit address space.
>
> Change find_free_bus_resource() to do the following:
> - Return first unassigned resource of the correct type.
> - If none of the above, return first assigned resource of the correct type.
> - If none of the above, return NULL.
>
> Returning an assigned resource of the correct type allows the caller to
> distinguish between already assigned and no resource of the correct type.
>
> Rename find_free_bus_resource to find_bus_resource_of_type().
>
> Add checks in pbus_size_io() and pbus_size_mem() to return success if
> resource returned from find_free_bus_resource() is already allocated.
>
> This avoids pbus_size_io() and pbus_size_mem() returning error code to
> __pci_bus_size_bridges() when a resource has been successfully assigned
> in a previous pass. This fixes the existing behaviour where space for a
> resource could be reserved multiple times in different parent bridge
> windows.
>
> Link: https://lore.kernel.org/lkml/20190531171216.20532-2-logang@deltatee.com/T/#u
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=203243
>
> Reported-by: Kit Chow <kchow@...aio.com>
> Reported-by: Nicholas Johnson <nicholas.johnson-opensource@...look.com.au>
> Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@...look.com.au>
> Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
Applied with reviewed-by from Mika and Logan to pci/resource for v5.5,
thanks!
> ---
> drivers/pci/setup-bus.c | 38 +++++++++++++++++++++++++++-----------
> 1 file changed, 27 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index 6b64bf909..f382f449b 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -752,24 +752,32 @@ static void pci_bridge_check_ranges(struct pci_bus *bus)
> }
>
> /*
> - * Helper function for sizing routines: find first available bus resource
> - * of a given type. Note: we intentionally skip the bus resources which
> - * have already been assigned (that is, have non-NULL parent resource).
> + * Helper function for sizing routines.
> + * Assigned resources have non-NULL parent resource.
> + *
> + * Return first unassigned resource of the correct type.
> + * If none of the above, return first assigned resource of the correct type.
> + * If none of the above, return NULL.
> + *
> + * Returning an assigned resource of the correct type allows the caller to
> + * distinguish between already assigned and no resource of the correct type.
> */
> -static struct resource *find_free_bus_resource(struct pci_bus *bus,
> - unsigned long type_mask,
> - unsigned long type)
> +static struct resource *find_bus_resource_of_type(struct pci_bus *bus,
> + unsigned long type_mask,
> + unsigned long type)
> {
> + struct resource *r, *r_assigned = NULL;
> int i;
> - struct resource *r;
>
> pci_bus_for_each_resource(bus, r, i) {
> if (r == &ioport_resource || r == &iomem_resource)
> continue;
> if (r && (r->flags & type_mask) == type && !r->parent)
> return r;
> + if (r && (r->flags & type_mask) == type && !r_assigned)
> + r_assigned = r;
> }
> - return NULL;
> + return r_assigned;
> }
>
> static resource_size_t calculate_iosize(resource_size_t size,
> @@ -866,8 +874,8 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size,
> struct list_head *realloc_head)
> {
> struct pci_dev *dev;
> - struct resource *b_res = find_free_bus_resource(bus, IORESOURCE_IO,
> - IORESOURCE_IO);
> + struct resource *b_res = find_bus_resource_of_type(bus, IORESOURCE_IO,
> + IORESOURCE_IO);
> resource_size_t size = 0, size0 = 0, size1 = 0;
> resource_size_t children_add_size = 0;
> resource_size_t min_align, align;
> @@ -875,6 +883,10 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size,
> if (!b_res)
> return;
>
> + /* If resource is already assigned, nothing more to do. */
> + if (b_res->parent)
> + return;
> +
> min_align = window_alignment(bus, IORESOURCE_IO);
> list_for_each_entry(dev, &bus->devices, bus_list) {
> int i;
> @@ -978,7 +990,7 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
> resource_size_t min_align, align, size, size0, size1;
> resource_size_t aligns[18]; /* Alignments from 1MB to 128GB */
> int order, max_order;
> - struct resource *b_res = find_free_bus_resource(bus,
> + struct resource *b_res = find_bus_resource_of_type(bus,
> mask | IORESOURCE_PREFETCH, type);
> resource_size_t children_add_size = 0;
> resource_size_t children_add_align = 0;
> @@ -987,6 +999,10 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
> if (!b_res)
> return -ENOSPC;
>
> + /* If resource is already assigned, nothing more to do. */
> + if (b_res->parent)
> + return 0;
> +
> memset(aligns, 0, sizeof(aligns));
> max_order = 0;
> size = 0;
> --
> 2.24.0
>
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