On Tuesday 12 January 2016 18:38:54 Lorenzo Pieralisi wrote: > On Tue, Jan 12, 2016 at 03:30:25PM +0100, Arnd Bergmann wrote: > > On Monday 11 January 2016 10:56:30 Sinan Kaya wrote: > > > > > > #_dmesg_|_grep_resource > > > [ 2.945762] pci_bus 0000:00: root bus resource [io 0x0000-0xefff window] (bus address [0x1000-0xffff]) > > > [ 3.652201] pci_bus 0002:00: root bus resource [io 0xf000-0x1dfff window] (bus address [0x1000-0xffff]) > > > [ 6.546716] pci_bus 0006:00: root bus resource [io 0x1e000-0x2cfff window] (bus address [0x1000-0xffff]) > > > / # > > > > This is bad. We normally want to stay out of the first 0x1000 bytes of > > the Linux space, to prevent drivers from poking into the ISA > > registers. > > You are referring to: > > pci_bus 0000:00: root bus resource [io 0x0000-0xefff window] > ^^^^^^ > here, right ? [0x0 - PCIBIOS_MIN_IO] is not assigned by the PCI > code that reassigns resources anyway, so devices with IO BARs won't > get assigned [0x0 - PCIBIOS_MIN_IO] address space (Linux space). > > Are you saying we should disallow the [0x0 - 0x1000] in the PCI busses > IO resource (Linux space) ? > > In pci_address_to_pio() the offset (Linux IO resource) we assign starts > from 0x0, so we always allocate that chunk of IO address space (that is > an offset into the Linux virtual address space), am I correct ? I think we can assign the address zero of the Linux I/O port range, but we should never assign it to a bus port range that does not also start at zero. If we encounter a firmware description that has bus range which excludes the first 1k, we should probably assign it to somewhere after 0x10000 (65536), so we can later assign a primary I/O space to a bus that has an ISA or LPC bridge with actual devices below 0x1000 (4096). > > We can have one of the buses be the "primary" bus that has its first > > 0x1000 bytes of I/O space mapped into the respective Linux addresses, > > but mapping the second 0x1000 bytes into the reserved space is the > > worst possible outcome here, as legacy ISA drivers will now poke at > > random other devices that are intentionally moved to high addresses to > > stay of of that range. > > And you are referring to: > > root bus resource [io 0x0000-0xefff window] (bus address [0x1000-0xffff]) > ^^^^^^ ^^^^^^ > > here ? If ISA drivers poke at addresses in the [0x0 - 0x1000] > range (Linux space IO offset) they end up on the PCI bus with addresses > above 0x1000, is that what you are saying when you refer to "moved to > high addresses to stay out of that range" ? Correct. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
