[+cc Catalin, Will, linux-arm-kernel] On Tue, Mar 26, 2019 at 04:33:55PM +0000, John Garry wrote: > On 25/03/2019 23:32, Bjorn Helgaas wrote: > > 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. > > ok > > > > 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. > > From my checking, the f71882fg hwmon is accessed via the super-io interface > on the PCH on x86. The super-io interface is at fixed addresses, those being > 0x2e and 0x4e. > > Please see the following: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/hwmon/f71805f.c?h=v5.1-rc2#n1621 > > and > > https://www.intel.com/content/dam/www/public/us/en/documents/datasheets/8-series-chipset-pch-datasheet.pdf > (Table 9.2). > > On x86 systems, these PCH IO ports will be mapped on a PCI bus, like: > > $more /proc/ioports > 0000-0cf7 : PCI Bus 0000:00 > 0000-001f : dma1 > 0020-0021 : pic1 > 0040-0043 : timer0 > 0050-0053 : timer1 > 0060-0060 : keyboard > 0064-0064 : keyboard > 0070-0077 : rtc0 > 0080-008f : dma page reg > 00a0-00a1 : pic2 > 00c0-00df : dma2 > 00f0-00ff : fpu > > So, the idea in the patch is that if PCI Bus 0000:00 does not exist because > of no PCI host, then we should fail a request to an IO port region. I'm not convinced about this last sentence. It's true that on most modern systems, including that Intel PCH, the Super I/O controller is attached via an LPC bridge on a PCI bus. But I don't think it's an actual requirement that PCI be involved. There certainly once were systems, e.g., PC/104, that had ISA devices but no PCI. Maybe Super I/O attached via ISA is obsolete enough that we don't care any more, but I really don't know. > > On x86, I think inb/inw/inl from a port where nothing responds > > probably just returns ~0, and outb/outw/outl just get dropped. > > Shouldn't arm64 do the same, without crashing? > > That would be ideal and we're doing something similar in patch 2/3. > > So on ARM64 we have to IO remap the PCI IO resource. If this mapping is not > done (due to no PCI host), then any inb/inw/inl calls will crash the system. My take is that ARM64 is responsible for implementing inb/inw/inl in such a way that they don't crash. I don't think it's practical to update all the old ISA drivers or even the core code to work around that. > So in patch 2/3, I am also making the change to the logical PIO inb/inw/inl > accessors to discard accesses when no PCI MMIO regions are registered in > logical PIO space. > > This is really a second line of defense (this patch being the first). > > > > root@(none)$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)$ > > > > > 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. > > ok, I hope that I can find this old thread. The beauty of lore.kernel.org is that the URL contains the Message-ID, so it's easy build the URL and it would contain useful information even if lore.kernel.org disappeared: https://lore.kernel.org/linux-pci/56F209A9.4040304@xxxxxxxxxx Bjorn > > > Signed-off-by: John Garry <john.garry@xxxxxxxxxx> > > > --- > > Thanks! > > > > include/linux/ioport.h | 12 +++++++++--- > > > kernel/resource.c | 28 ++++++++++++++++++++++++++++ > > > 2 files changed, 37 insertions(+), 3 deletions(-) > > > > > Leaving remaing text as a reference. > > > > 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 > > > > > > > . > > > >
