On 14.10.2013, at 15:24, Marc Zyngier <marc.zyngier@xxxxxxx> wrote: > On 14/10/13 14:10, Alexander Graf wrote: >> >> On 14.10.2013, at 15:03, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: >> >>> Il 11/10/2013 16:36, Marc Zyngier ha scritto: >>>> This small patch series adds just enough kernel infrastructure and >>>> fixes to allow a BE guest to use virtio-mmio on a LE host, provided >>>> that the host actually supports such madness. >>> >>> More precisely, it allows the guest drivers to pick the endianness they >>> prefer. Mixed-endian virtio works fine on QEMU with e.g. a mips guest >>> in emulation mode, because then any given QEMU binary will always use >>> the same endianness (e.g. big for qemu-system-mips). >> >> We have the same problem (runtime switchable endianness) on PowerPC. IBM POWER is gaining Little Endian support in Linux now, so we could easily end up with an LE guest on a BE host. >> >> IIRC the way we're going to solve this is to hack up virtio_is_big_endian() to evaluate the first CPU's endianness mode (which will always be the same as all other CPU's endianness mode due to hypercall restrictions). > > I have implemented something similar for MMIO emulation in KVM/arm > (except that I only care about the faulting CPU). > > See my initial patch for that: > https://lists.cs.columbia.edu/pipermail/kvmarm/2013-October/007359.html > > That doesn't really change the non-trapping virtio accesses, though. > Where is this virtio_is_big_endian() thing? It's in QEMU's exec.c. It only gets used for config space access that goes through PCI though. Is there any other place where virtio specifies native endianness today? Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
