On Fri, Mar 14 2014 at 4:27:56 am GMT, Christoffer Dall <christoffer.dall@xxxxxxxxxx> wrote: > On Tue, Jan 28, 2014 at 08:28:42AM -0800, Christoffer Dall wrote: >> The KVM API documentation is not clear about the semantics of the data >> field on the mmio struct on the kvm_run struct. >> >> This has become problematic when supporting ARM guests on big-endian >> host systems with guests of both endianness types, because it is unclear >> how the data should be exported to user space. >> >> This should not break with existing implementations as all supported >> existing implementations of known user space applications (QEMU and >> kvmtools for virtio) only support default endianness of the >> architectures on the host side. >> >> Cc: Marc Zyngier <marc.zyngier@xxxxxxx> >> Cc: Peter Maydell <peter.maydell@xxxxxxxxxx> >> Cc: Alexander Graf <agraf@xxxxxxx> >> Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx> >> --- >> Changes [v2 - v3]: >> - Change the semantics and wordings as per Scott's, Avi's, and Ben's >> suggestions. >> >> Changes [v1 - v2]: >> - s/host kernel should/host user space should/ >> >> Documentation/virtual/kvm/api.txt | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt >> index 366bf4b..e11f09d 100644 >> --- a/Documentation/virtual/kvm/api.txt >> +++ b/Documentation/virtual/kvm/api.txt >> @@ -2565,6 +2565,10 @@ executed a memory-mapped I/O instruction which could not be satisfied >> by kvm. The 'data' member contains the written data if 'is_write' is >> true, and should be filled by application code otherwise. >> >> +The 'data' member contains, in its first 'len' bytes, the value as it would >> +appear if the VCPU performed a load or store of the appropriate width directly >> +to the byte array. >> + >> NOTE: For KVM_EXIT_IO, KVM_EXIT_MMIO, KVM_EXIT_OSI, KVM_EXIT_DCR, >> KVM_EXIT_PAPR and KVM_EXIT_EPR the corresponding >> operations are complete (and guest state is consistent) only after userspace >> -- >> 1.8.5.2 >> > > Any more comments on this one, or can it be applied? I think we should go ahead and apply this. Having dark corners in the ABI is not a very good thing, and bi-endianness seems to be quite fashionnable these days... ;-) Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx> M. -- Jazz is not dead. It just smells funny. -- 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
