Avi Kivity wrote: > Beth Kon wrote: >> Signed-off-by: Beth Kon <[email protected]> >> >> > > Please write a few words on what this patch does and why. > >> --- >> arch/x86/include/asm/kvm.h | 1 + >> arch/x86/kvm/i8254.c | 24 +++++++++++++++++++----- >> arch/x86/kvm/i8254.h | 3 ++- >> arch/x86/kvm/x86.c | 5 ++++- >> 4 files changed, 26 insertions(+), 7 deletions(-) >> >> diff --git a/arch/x86/include/asm/kvm.h b/arch/x86/include/asm/kvm.h >> index 708b9c3..3c44923 100644 >> --- a/arch/x86/include/asm/kvm.h >> +++ b/arch/x86/include/asm/kvm.h >> @@ -235,6 +235,7 @@ struct kvm_guest_debug_arch { >> >> struct kvm_pit_state { >> struct kvm_pit_channel_state channels[3]; >> + u8 hpet_legacy_mode; >> }; >> > > This changes the ABI, breaking older binaries running on newer kernels, > or newer binaries running on older kernels.
As we have KVM_CREATE_PIT2 now, which includes struct kvm_pit_config with a lot of unused flags, it should be straightforward to negotiate the kvm_pit_state format between kernel and user space: kernel advertises support for the new one via capability, user space requests it via a bit in kvm_pit_state.flags. Jan
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