On 22.07.2013, at 22:16, Hervé Poussineau wrote: > Paolo Bonzini a écrit : >> Il 22/07/2013 17:04, Peter Maydell ha scritto: >>> On 22 July 2013 15:36, Paolo Bonzini <pbonz...@redhat.com> wrote: >>>> Il 22/07/2013 16:32, Peter Maydell ha scritto: >>>>> In the long term it would be good to identify which boards >>>>> were using isa_mmio purely for the benefit of old_portio >>>>> (which I think is basically "boards where the CPU has no >>>>> concept of port I/O instructions"). >>>> All of them. Only i386/x86_64 has I/O space, as far as I know. >>> Sounds plausible. I had wondered if our ISA bus infrastructure >>> assumed that ISA device IO ports live in the system IO space, >>> but it doesn't. >> No, luckily it doesn't, and neither should the PCI-to-ISA bridges as you >> found out---they do not after these patches. PReP is an exception, but >> I think it could be rewritten to use an IOMMU memory region. > > PReP PCI I/O area is located at 0x80000000, up to 0xbf7fffff (in main memory > space region), while ISA I/O area is at 0x80000000, up to 0x8000ffff > (size=64KB)
Are you sure the ISA I/O space isn't just the first part of the PCI ioport range? > > However, as they are overlapped, some strange things can happen. > For example, IBM 40p firmware configures the PCI SCSI bar at 0x20000000 (ie > 0xa0000000 in main memory), while Linux sets bar to 0x1000 (ie 0x80001000 in > main memory), ie also in ISA I/O space. > > I don't know exactly what you mean by an "IOMMU memory region", but how would > you modelize it, so that 0x80001000 and 0xa0000000 accesses are redirected to > PCI SCSI card, while 0x800003f8 redirects (for example) to an ISA serial port? From what you're saying they both really live on the same address range. > If you create a new memory region for ISA I/O space, and you redirect all > accesses from 0x80000000-0x8000ffff to this new address space, 0x80001000 > won't work to access the SCSI I/O bar (located in the PCI I/O address space). > > That's why I think the i82378 device should not create a whole new address > space for ISA I/O space, but use the first 64KB of the PCI I/O space. Exactly :). Or the other way around really, if that's easier to model. Alex
