On Wed, Jan 20, 2016 at 05:44:49PM +0300, Denis V. Lunev wrote: > On 01/20/2016 05:05 PM, Paolo Bonzini wrote: > > > >On 19/01/2016 08:48, Denis V. Lunev wrote: > >>>diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > >>>index 6877b4d7e..93c9e25 100644 > >>>--- a/include/linux/kvm_host.h > >>>+++ b/include/linux/kvm_host.h > >>>@@ -145,6 +145,7 @@ static inline bool is_error_page(struct page *page) > >>> #define KVM_REQ_HV_RESET 29 > >>> #define KVM_REQ_HV_EXIT 30 > >>> #define KVM_REQ_HV_STIMER 31 > >>>+#define KVM_REQ_HV_TSC_PAGE 32 > >>> #define KVM_REQ_MAX 64 > >>ping > >Applied with this change: > > > >diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c > >index d7716c6e2752..047c275717d3 100644 > >--- a/arch/x86/kvm/hyperv.c > >+++ b/arch/x86/kvm/hyperv.c > >@@ -842,7 +842,7 @@ int kvm_hv_setup_tsc_page(struct kvm_vcpu *vcpu) > > tsc_khz, tsc, tsc_scale, tsc_offset); > > tsc_ref.tsc_sequence++; > >- if (tsc_ref.tsc_sequence == 0) > >+ if (tsc_ref.tsc_sequence == 0xFFFFFFFF tsc_ref.tsc_sequence == 0) > > tsc_ref.tsc_sequence = 1; > > tsc_ref.tsc_scale = tsc_scale; > > > >and renumbering KVM_REQ_HV_TSC_PAGE from 32 to 31. > > > >Paolo > the latter does not seem to be correct to me. > MS spec has bug, see this thread: > https://lkml.org/lkml/2015/11/2/655 > and the change was Acked-by: K.Y. What happens in the patched code is this: when the sequence counter wraps around and hits an invalid value, skip to the next valid one. I think Paolo wanted to be compatible not only with the de facto implementation in Windows Hyper-V guests, but also with the Linux driver which followed the buggy spec and thought 0xFFFFFFFF to be invalid. So the change is fine (as long as there's || rather than a space there ;) Thanks, Roman. -- 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
