Message-ID: <20190325233255.GF24180@google.com>
Date:   Mon, 25 Mar 2019 18:32:55 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     John Garry <john.garry@...wei.com>
Cc:     rafael@...nel.org, arnd@...db.de, lorenzo.pieralisi@....com,
        bp@...e.de, linux@...ck-us.net, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, wangkefeng.wang@...wei.com,
        linuxarm@...wei.com, agraf@...e.de, andy.shevchenko@...il.com
Subject: Re: [RFC PATCH v2 1/3] resource: Request IO port regions from
 children of ioport_resource

Hi John,

On Thu, Mar 21, 2019 at 02:14:08AM +0800, John Garry wrote:
> Currently when we request an IO port region, the request is made directly
> to the top resource, ioport_resource.

Let's be explicit here, e.g.,

  Currently request_region() requests an IO port region directly from the
  top resource, ioport_resource.

> There is an issue here, in that drivers may successfully request an IO
> port region even if the IO port region has not even been mapped in
> (in pci_remap_iospace()).
> 
> This may lead to crashes when the system has no PCI host, or, has a host
> but it has failed enumeration, while drivers still attempt to access PCI
> IO ports, as below:

I don't understand the strategy here.  f71882fg is not a driver for a
PCI device, so it should work even if there is no PCI host in the
system.

On x86, I think inb/inw/inl from a port where nothing responds
probably just returns ~0, and outb/outw/outl just get dropped.
Shouldn't arm64 do the same, without crashing?

> root@(none)$root@(none)$ insmod f71882fg.ko
> [  152.215377] Unable to handle kernel paging request at virtual address ffff7dfffee0002e
> [  152.231299] Mem abort info:
> [  152.236898]   ESR = 0x96000046
> [  152.243019]   Exception class = DABT (current EL), IL = 32 bits
> [  152.254905]   SET = 0, FnV = 0
> [  152.261024]   EA = 0, S1PTW = 0
> [  152.267320] Data abort info:
> [  152.273091]   ISV = 0, ISS = 0x00000046
> [  152.280784]   CM = 0, WnR = 1
> [  152.286730] swapper pgtable: 4k pages, 48-bit VAs, pgdp = (____ptrval____)
> [  152.300537] [ffff7dfffee0002e] pgd=000000000141c003, pud=000000000141d003, pmd=0000000000000000
> [  152.318016] Internal error: Oops: 96000046 [#1] PREEMPT SMP
> [  152.329199] Modules linked in: f71882fg(+)
> [  152.337415] CPU: 8 PID: 2732 Comm: insmod Not tainted 5.1.0-rc1-00002-gab1a0e9200b8-dirty #102
> [  152.354712] Hardware name: Huawei Taishan 2280 /D05, BIOS Hisilicon D05 IT21 Nemo 2.0 RC0 04/18/2018
> [  152.373058] pstate: 80000005 (Nzcv daif -PAN -UAO)
> [  152.382675] pc : logic_outb+0x54/0xb8
> [  152.390017] lr : f71882fg_find+0x64/0x390 [f71882fg]
> [  152.399977] sp : ffff000013393aa0
> [  152.406618] x29: ffff000013393aa0 x28: ffff000008b98b10
> [  152.417278] x27: ffff000013393df0 x26: 0000000000000100
> [  152.427938] x25: ffff801f8c872d30 x24: ffff000011420000
> [  152.438598] x23: ffff801fb49d2940 x22: ffff000011291000
> [  152.449257] x21: 000000000000002e x20: 0000000000000087
> [  152.459917] x19: ffff000013393b44 x18: ffffffffffffffff
> [  152.470577] x17: 0000000000000000 x16: 0000000000000000
> [  152.481236] x15: ffff00001127d6c8 x14: ffff801f8cfd691c
> [  152.491896] x13: 0000000000000000 x12: 0000000000000000
> [  152.502555] x11: 0000000000000003 x10: 0000801feace2000
> [  152.513215] x9 : 0000000000000000 x8 : ffff841fa654f280
> [  152.523874] x7 : 0000000000000000 x6 : 0000000000ffc0e3
> [  152.534534] x5 : ffff000011291360 x4 : ffff801fb4949f00
> [  152.545194] x3 : 0000000000ffbffe x2 : 76e767a63713d500
> [  152.555853] x1 : ffff7dfffee0002e x0 : ffff7dfffee00000
> [  152.566514] Process insmod (pid: 2732, stack limit = 0x(____ptrval____))
> [  152.579968] Call trace:
> [  152.584863]  logic_outb+0x54/0xb8
> [  152.591506]  f71882fg_find+0x64/0x390 [f71882fg]
> [  152.600768]  f71882fg_init+0x38/0xc70 [f71882fg]
> [  152.610031]  do_one_initcall+0x5c/0x198
> [  152.617723]  do_init_module+0x54/0x1b0
> [  152.625237]  load_module+0x1dc4/0x2158
> [  152.632752]  __se_sys_init_module+0x14c/0x1e8
> [  152.641490]  __arm64_sys_init_module+0x18/0x20
> [  152.650404]  el0_svc_common+0x5c/0x100
> [  152.657919]  el0_svc_handler+0x2c/0x80
> [  152.665433]  el0_svc+0x8/0xc
> [  152.671202] Code: d2bfdc00 f2cfbfe0 f2ffffe0 8b000021 (39000034)
> [  152.683434] ---[ end trace fd4f35b610829a48 ]---
> Segmentation fault
> root@(none)$

Please remove the timestamps (because they don't contribute useful
information) and indent the example a couple spaces (which is
conventional for quoted material).

> Note that the f71882fg driver correctly calls request_muxed_region().
> 
> This issue was originally reported in [1].
> 
> This patch changes the functionality of request{muxed_}_region() to
> request a region from a direct child descendent of the top
> ioport_resource.
> 
> In this, if the IO port region has not been mapped for a particular IO
> region, the PCI IO resource would also not have been inserted, and so a
> suitable child region will not exist. As such,
> request_{muxed_}region() calls will fail.
> 
> A side note: there are many drivers in the kernel which fail to even call
> request_{muxed_}region() prior to IO port accesses, and they also need to
> be fixed (to call request_{muxed_}region(), as appropriate) separately.
> 
> [1] https://www.spinics.net/lists/linux-pci/msg49821.html

Please use a https://lore.kernel.org/ URL instead of spinics.net.

> Signed-off-by: John Garry <john.garry@...wei.com>
> ---
>  include/linux/ioport.h | 12 +++++++++---
>  kernel/resource.c      | 28 ++++++++++++++++++++++++++++
>  2 files changed, 37 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index da0ebaec25f0..d7b7e1e08291 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -217,19 +217,25 @@ static inline bool resource_contains(struct resource *r1, struct resource *r2)
>  
>  
>  /* Convenience shorthand with allocation */
> -#define request_region(start,n,name)		__request_region(&ioport_resource, (start), (n), (name), 0)
> -#define request_muxed_region(start,n,name)	__request_region(&ioport_resource, (start), (n), (name), IORESOURCE_MUXED)
> +#define request_region(start,n,name)		__request_region_from_children(&ioport_resource, (start), (n), (name), 0)
> +#define request_muxed_region(start,n,name)	__request_region_from_children(&ioport_resource, (start), (n), (name), IORESOURCE_MUXED)
>  #define __request_mem_region(start,n,name, excl) __request_region(&iomem_resource, (start), (n), (name), excl)
>  #define request_mem_region(start,n,name) __request_region(&iomem_resource, (start), (n), (name), 0)
>  #define request_mem_region_exclusive(start,n,name) \
>  	__request_region(&iomem_resource, (start), (n), (name), IORESOURCE_EXCLUSIVE)
>  #define rename_region(region, newname) do { (region)->name = (newname); } while (0)
>  
> -extern struct resource * __request_region(struct resource *,
> +extern struct resource *__request_region(struct resource *,
>  					resource_size_t start,
>  					resource_size_t n,
>  					const char *name, int flags);
>  
> +extern struct resource *__request_region_from_children(struct resource *,
> +					resource_size_t start,
> +					resource_size_t n,
> +					const char *name, int flags);
> +
> +
>  /* Compatibility cruft */
>  #define release_region(start,n)	__release_region(&ioport_resource, (start), (n))
>  #define release_mem_region(start,n)	__release_region(&iomem_resource, (start), (n))
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 92190f62ebc5..87ed200eda8b 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -1097,6 +1097,34 @@ resource_size_t resource_alignment(struct resource *res)
>  
>  static DECLARE_WAIT_QUEUE_HEAD(muxed_resource_wait);
>  
> +/**
> + * __request_region_from_children - create a new busy region from a child
> + * @parent: parent resource descriptor
> + * @start: resource start address
> + * @n: resource region size
> + * @name: reserving caller's ID string
> + * @flags: IO resource flags
> + */
> +struct resource *__request_region_from_children(struct resource *parent,
> +						resource_size_t start,
> +						resource_size_t n,
> +						const char *name, int flags)
> +{
> +	struct resource *res = __request_region(parent, start, n, name, flags);
> +
> +	if (res && res->parent == parent) {
> +		/*
> +		 * This is a direct descendent of the parent, which is
> +		 * what we didn't want.
> +		 */
> +		__release_region(parent, start, n);
> +		res = NULL;
> +	}
> +
> +	return res;
> +}
> +EXPORT_SYMBOL(__request_region_from_children);
> +
>  /**
>   * __request_region - create a new busy resource region
>   * @parent: parent resource descriptor
> -- 
> 2.17.1
> 

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