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? Thanks, -- Christoffer -- 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
