From 6acdb1603a7db4c1b5d91863a13d2c3f1b9188b0 Mon Sep 17 00:00:00 2001 From: Christoffer Dall Date: Tue, 28 Jan 2014 08:28:42 -0800 Subject: KVM: Specify byte order for KVM_EXIT_MMIO 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 Cc: Peter Maydell Cc: Alexander Graf Signed-off-by: Christoffer Dall Signed-off-by: Paolo Bonzini --- Documentation/virtual/kvm/api.txt | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'Documentation/virtual') diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt index 2cb1640a90ad..c24211da4120 100644 --- a/Documentation/virtual/kvm/api.txt +++ b/Documentation/virtual/kvm/api.txt @@ -2595,6 +2595,10 @@ 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 -- cgit