On Wed, Mar 4, 2020 at 3:51 PM Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> wrote:
>
> Jon Doron <arilou@xxxxxxxxx> writes:
>
> > Add support for Hyper-V synthetic debugger (syndbg) interface.
> > The syndbg interface is using MSRs to emulate a way to send/recv packets
> > data.
> >
> > The debug transport dll (kdvm/kdnet) will identify if Hyper-V is enabled
> > and if it supports the synthetic debugger interface it will attempt to
> > use it, instead of trying to initialize a network adapter.
> >
>
> Cc: linux-hyperv@ list where Hyper-V folks live :-) They're in charge of
> 'hyperv-tlfs.h' so an ACK from them will be needed.
>
Thanks will do in next version of this patchset.
> > Signed-off-by: Jon Doron <arilou@xxxxxxxxx>
> > ---
> > arch/x86/include/asm/hyperv-tlfs.h | 16 +++++
> > arch/x86/include/asm/kvm_host.h | 11 +++
> > arch/x86/kvm/hyperv.c | 109 +++++++++++++++++++++++++++++
> > arch/x86/kvm/hyperv.h | 5 ++
> > arch/x86/kvm/trace.h | 22 ++++++
> > arch/x86/kvm/x86.c | 8 +++
> > include/uapi/linux/kvm.h | 9 +++
> > 7 files changed, 180 insertions(+)
> >
> > diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> > index 92abc1e42bfc..8efdf974c23f 100644
> > --- a/arch/x86/include/asm/hyperv-tlfs.h
> > +++ b/arch/x86/include/asm/hyperv-tlfs.h
> > @@ -33,6 +33,9 @@
> > #define HYPERV_CPUID_ENLIGHTMENT_INFO 0x40000004
> > #define HYPERV_CPUID_IMPLEMENT_LIMITS 0x40000005
> > #define HYPERV_CPUID_NESTED_FEATURES 0x4000000A
> > +#define HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS 0x40000080
> > +#define HYPERV_CPUID_SYNDBG_INTERFACE 0x40000081
> > +#define HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES 0x40000082
>
> Out of pure curiosity, are these CPUIDs and MSRs documented somewhere?
> I'm looking at TLFS v6.0 and failing to see them...
>
Basically a lot of playing around with KDVM/KDNet by setting a kernel
debugger, there are
also few hints about how the transport for KD works in the DDK (there
are samples that
show how to code a new kdtransport)
> >
> > #define HYPERV_HYPERVISOR_PRESENT_BIT 0x80000000
> > #define HYPERV_CPUID_MIN 0x40000005
> > @@ -131,6 +134,8 @@
> > #define HV_FEATURE_FREQUENCY_MSRS_AVAILABLE BIT(8)
> > /* Crash MSR available */
> > #define HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE BIT(10)
> > +/* Support for debug MSRs available */
> > +#define HV_FEATURE_DEBUG_MSRS_AVAILABLE BIT(11)
> > /* stimer Direct Mode is available */
> > #define HV_STIMER_DIRECT_MODE_AVAILABLE BIT(19)
> >
> > @@ -194,6 +199,9 @@
> > #define HV_X64_NESTED_GUEST_MAPPING_FLUSH BIT(18)
> > #define HV_X64_NESTED_MSR_BITMAP BIT(19)
> >
> > +/* Hyper-V synthetic debugger platform capabilities */
> > +#define HV_X64_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING BIT(1)
> > +
> > /* Hyper-V specific model specific registers (MSRs) */
> >
> > /* MSR used to identify the guest OS. */
> > @@ -267,6 +275,14 @@
> > /* Hyper-V guest idle MSR */
> > #define HV_X64_MSR_GUEST_IDLE 0x400000F0
> >
> > +/* Hyper-V Synthetic debug options MSR */
> > +#define HV_X64_MSR_SYNDBG_CONTROL 0x400000F1
> > +#define HV_X64_MSR_SYNDBG_STATUS 0x400000F2
> > +#define HV_X64_MSR_SYNDBG_SEND_BUFFER 0x400000F3
> > +#define HV_X64_MSR_SYNDBG_RECV_BUFFER 0x400000F4
> > +#define HV_X64_MSR_SYNDBG_PENDING_BUFFER 0x400000F5
> > +#define HV_X64_MSR_SYNDBG_OPTIONS 0x400000FF
> > +
> > /* Hyper-V guest crash notification MSR's */
> > #define HV_X64_MSR_CRASH_P0 0x40000100
> > #define HV_X64_MSR_CRASH_P1 0x40000101
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 98959e8cd448..2b755174d683 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -854,6 +854,15 @@ struct kvm_apic_map {
> > struct kvm_lapic *phys_map[];
> > };
> >
> > +/* Hyper-V synthetic debugger (SynDbg)*/
> > +struct kvm_hv_syndbg {
> > + u64 control;
> > + u64 status;
> > + u64 send_page;
> > + u64 recv_page;
> > + u64 pending_page;
> > +};
> > +
> > /* Hyper-V emulation context */
> > struct kvm_hv {
> > struct mutex hv_lock;
> > @@ -877,6 +886,8 @@ struct kvm_hv {
> > atomic_t num_mismatched_vp_indexes;
> >
> > struct hv_partition_assist_pg *hv_pa_pg;
> > + u64 hv_syndbg_options;
> > + struct kvm_hv_syndbg hv_syndbg;
>
> I would've encapsulated both to struct kvm_hv_syndbg, e.g.
>
> struct kvm_hv_syndbg {
> struct {
> u64 control;
> u64 status;
> u64 send_page;
> u64 recv_page;
> u64 pending_page;
> } control;
> u64 options;
> }
>
> To make it clear they're part of the same thing (are they?) I see you
> handle HV_X64_MSR_SYNDBG_OPTIONS differently (outside of
> syndbg_set_msr()).
>
Done.
> > };
> >
> > enum kvm_irqchip_mode {
> > diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> > index a86fda7a1d03..13176ec23496 100644
> > --- a/arch/x86/kvm/hyperv.c
> > +++ b/arch/x86/kvm/hyperv.c
> > @@ -266,6 +266,66 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
> > return ret;
> > }
> >
> > +static int kvm_hv_syndbg_complete_userspace(struct kvm_vcpu *vcpu)
> > +{
> > + struct kvm *kvm = vcpu->kvm;
> > + struct kvm_hv *hv = &kvm->arch.hyperv;
> > +
> > + if (vcpu->run->hyperv.u.syndbg.msr == HV_X64_MSR_SYNDBG_CONTROL)
> > + hv->hv_syndbg.status = vcpu->run->hyperv.u.syndbg.status;
> > + return 1;
> > +}
> > +
> > +static void syndbg_exit(struct kvm_vcpu *vcpu, u32 msr)
> > +{
> > + struct kvm_hv_syndbg *syndbg = vcpu_to_hv_syndbg(vcpu);
> > + struct kvm_vcpu_hv *hv_vcpu = &vcpu->arch.hyperv;
> > +
> > + hv_vcpu->exit.type = KVM_EXIT_HYPERV_SYNDBG;
> > + hv_vcpu->exit.u.syndbg.msr = msr;
> > + hv_vcpu->exit.u.syndbg.control = syndbg->control;
> > + hv_vcpu->exit.u.syndbg.send_page = syndbg->send_page;
> > + hv_vcpu->exit.u.syndbg.recv_page = syndbg->recv_page;
> > + hv_vcpu->exit.u.syndbg.pending_page = syndbg->pending_page;
> > + vcpu->arch.complete_userspace_io =
> > + kvm_hv_syndbg_complete_userspace;
> > +
> > + kvm_make_request(KVM_REQ_HV_EXIT, vcpu);
>
> This new interface requires userspace support apparently so we can't
> enable it unconditionally (userspaces which don't support it will be
> very confused). You need to introduce a capability
> (KVM_CAP_HYPERV_DEBUGGING?)
>
Done.
> > +}
> > +
> > +static int syndbg_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> > +{
> > + struct kvm_hv_syndbg *syndbg = vcpu_to_hv_syndbg(vcpu);
> > + int ret;
> > +
> > + trace_kvm_hv_syndbg_set_msr(vcpu->vcpu_id, msr, data);
> > + ret = 0;
> > + switch (msr) {
> > + case HV_X64_MSR_SYNDBG_CONTROL:
> > + syndbg->control = data;
> > + syndbg_exit(vcpu, msr);
> > + break;
> > + case HV_X64_MSR_SYNDBG_STATUS:
> > + syndbg->status = data;
> > + break;
> > + case HV_X64_MSR_SYNDBG_SEND_BUFFER:
> > + syndbg->send_page = data;
> > + break;
> > + case HV_X64_MSR_SYNDBG_RECV_BUFFER:
> > + syndbg->recv_page = data;
> > + break;
> > + case HV_X64_MSR_SYNDBG_PENDING_BUFFER:
> > + syndbg->pending_page = data;
> > + syndbg_exit(vcpu, msr);
> > + break;
> > + default:
> > + ret = 1;
> > + break;
> > + }
> > +
> > + return ret;
> > +}
> > +
> > static int synic_get_msr(struct kvm_vcpu_hv_synic *synic, u32 msr, u64 *pdata,
> > bool host)
> > {
> > @@ -800,6 +860,8 @@ static bool kvm_hv_msr_partition_wide(u32 msr)
> > case HV_X64_MSR_REENLIGHTENMENT_CONTROL:
> > case HV_X64_MSR_TSC_EMULATION_CONTROL:
> > case HV_X64_MSR_TSC_EMULATION_STATUS:
> > + case HV_X64_MSR_SYNDBG_OPTIONS:
> > + case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
> > r = true;
> > break;
> > }
> > @@ -1061,6 +1123,11 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
> > if (!host)
> > return 1;
> > break;
> > + case HV_X64_MSR_SYNDBG_OPTIONS:
> > + hv->hv_syndbg_options = data;
> > + break;
> > + case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
> > + return syndbg_set_msr(vcpu, msr, data);
> > default:
> > vcpu_unimpl(vcpu, "Hyper-V unhandled wrmsr: 0x%x data 0x%llx\n",
> > msr, data);
> > @@ -1227,6 +1294,24 @@ static int kvm_hv_get_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
> > case HV_X64_MSR_TSC_EMULATION_STATUS:
> > data = hv->hv_tsc_emulation_status;
> > break;
> > + case HV_X64_MSR_SYNDBG_OPTIONS:
> > + data = hv->hv_syndbg_options;
> > + break;
> > + case HV_X64_MSR_SYNDBG_CONTROL:
> > + data = hv->hv_syndbg.control;
> > + break;
> > + case HV_X64_MSR_SYNDBG_STATUS:
> > + data = hv->hv_syndbg.status;
> > + break;
> > + case HV_X64_MSR_SYNDBG_SEND_BUFFER:
> > + data = hv->hv_syndbg.send_page;
> > + break;
> > + case HV_X64_MSR_SYNDBG_RECV_BUFFER:
> > + data = hv->hv_syndbg.recv_page;
> > + break;
> > + case HV_X64_MSR_SYNDBG_PENDING_BUFFER:
> > + data = hv->hv_syndbg.pending_page;
> > + break;
> > default:
> > vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr);
> > return 1;
> > @@ -1797,6 +1882,9 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
> > { .function = HYPERV_CPUID_ENLIGHTMENT_INFO },
> > { .function = HYPERV_CPUID_IMPLEMENT_LIMITS },
> > { .function = HYPERV_CPUID_NESTED_FEATURES },
> > + { .function = HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS },
> > + { .function = HYPERV_CPUID_SYNDBG_INTERFACE },
> > + { .function = HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES },
>
> HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS now returns
> 'HYPERV_CPUID_NESTED_FEATURES' as the last available leaf and I don't
> see you adjusting it - is this expected?
>
Good catch my bad :)
> > };
> > int i, nent = ARRAY_SIZE(cpuid_entries);
> >
> > @@ -1856,9 +1944,12 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
> >
> > ent->ebx |= HV_X64_POST_MESSAGES;
> > ent->ebx |= HV_X64_SIGNAL_EVENTS;
> > + ent->ebx |= HV_X64_DEBUGGING;
> >
> > ent->edx |= HV_FEATURE_FREQUENCY_MSRS_AVAILABLE;
> > ent->edx |= HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE;
> > + ent->edx |= HV_X64_GUEST_DEBUGGING_AVAILABLE;
> > + ent->edx |= HV_FEATURE_DEBUG_MSRS_AVAILABLE;
> >
> > /*
> > * Direct Synthetic timers only make sense with in-kernel
> > @@ -1903,6 +1994,24 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
> >
> > break;
> >
> > + case HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS:
> > + memcpy(signature, "Microsoft VS", 12);
>
> Does this string matter? E.g. for HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS
> we call ourselves "Linux KVM Hv", I think we should do the same here.
>
Nope does not really matter since Userspace will override this anyway
> > +
> > + ent->eax = 0;
> > + ent->ebx = signature[0];
> > + ent->ecx = signature[1];
> > + ent->edx = signature[2];
> > + break;
> > +
> > + case HYPERV_CPUID_SYNDBG_INTERFACE:
> > + memcpy(signature, "VS#1\0\0\0\0\0\0\0\0", 12);
> > + ent->eax = signature[0];
> > + break;
> > +
> > + case HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES:
> > + ent->eax |= HV_X64_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING;
> > + break;
> > +
> > default:
> > break;
> > }
> > diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
> > index 757cb578101c..6a86151fac53 100644
> > --- a/arch/x86/kvm/hyperv.h
> > +++ b/arch/x86/kvm/hyperv.h
> > @@ -46,6 +46,11 @@ static inline struct kvm_vcpu *synic_to_vcpu(struct kvm_vcpu_hv_synic *synic)
> > return hv_vcpu_to_vcpu(container_of(synic, struct kvm_vcpu_hv, synic));
> > }
> >
> > +static inline struct kvm_hv_syndbg *vcpu_to_hv_syndbg(struct kvm_vcpu *vcpu)
> > +{
> > + return &vcpu->kvm->arch.hyperv.hv_syndbg;
> > +}
> > +
> > int kvm_hv_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host);
> > int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host);
> >
> > diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
> > index f194dd058470..235b9ab673a2 100644
> > --- a/arch/x86/kvm/trace.h
> > +++ b/arch/x86/kvm/trace.h
> > @@ -1515,6 +1515,28 @@ TRACE_EVENT(kvm_nested_vmenter_failed,
> > __print_symbolic(__entry->err, VMX_VMENTER_INSTRUCTION_ERRORS))
> > );
> >
> > +/*
> > + * Tracepoint for syndbg_set_msr.
> > + */
> > +TRACE_EVENT(kvm_hv_syndbg_set_msr,
> > + TP_PROTO(int vcpu_id, u32 msr, u64 data),
> > + TP_ARGS(vcpu_id, msr, data),
> > +
> > + TP_STRUCT__entry(
> > + __field(int, vcpu_id)
> > + __field(u32, msr)
> > + __field(u64, data)
> > + ),
> > +
> > + TP_fast_assign(
> > + __entry->vcpu_id = vcpu_id;
> > + __entry->msr = msr;
> > + __entry->data = data;
> > + ),
> > +
> > + TP_printk("vcpu_id %d msr 0x%x data 0x%llx",
> > + __entry->vcpu_id, __entry->msr, __entry->data)
>
> This doesn't give us any additional data trace_kvm_msr_* points are more
> or less the same. I think we can do better, e.g. for Hyper-V specific
> things log the processor's VP index.
>
Done.
> > +);
> > #endif /* _TRACE_KVM_H */
> >
> > #undef TRACE_INCLUDE_PATH
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 5de200663f51..9d4d72a88572 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -1214,6 +1214,10 @@ static const u32 emulated_msrs_all[] = {
> > HV_X64_MSR_VP_ASSIST_PAGE,
> > HV_X64_MSR_REENLIGHTENMENT_CONTROL, HV_X64_MSR_TSC_EMULATION_CONTROL,
> > HV_X64_MSR_TSC_EMULATION_STATUS,
> > + HV_X64_MSR_SYNDBG_OPTIONS,
> > + HV_X64_MSR_SYNDBG_CONTROL, HV_X64_MSR_SYNDBG_STATUS,
> > + HV_X64_MSR_SYNDBG_SEND_BUFFER, HV_X64_MSR_SYNDBG_RECV_BUFFER,
> > + HV_X64_MSR_SYNDBG_PENDING_BUFFER,
> >
> > MSR_KVM_ASYNC_PF_EN, MSR_KVM_STEAL_TIME,
> > MSR_KVM_PV_EOI_EN,
> > @@ -2906,6 +2910,8 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> > */
> > break;
> > case HV_X64_MSR_GUEST_OS_ID ... HV_X64_MSR_SINT15:
> > + case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
> > + case HV_X64_MSR_SYNDBG_OPTIONS:
> > case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
> > case HV_X64_MSR_CRASH_CTL:
> > case HV_X64_MSR_STIMER0_CONFIG ... HV_X64_MSR_STIMER3_COUNT:
> > @@ -3151,6 +3157,8 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> > msr_info->data = 0x20000000;
> > break;
> > case HV_X64_MSR_GUEST_OS_ID ... HV_X64_MSR_SINT15:
> > + case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
> > + case HV_X64_MSR_SYNDBG_OPTIONS:
> > case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
> > case HV_X64_MSR_CRASH_CTL:
> > case HV_X64_MSR_STIMER0_CONFIG ... HV_X64_MSR_STIMER3_COUNT:
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > index 4b95f9a31a2f..fae8cf608976 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -188,6 +188,7 @@ struct kvm_s390_cmma_log {
> > struct kvm_hyperv_exit {
> > #define KVM_EXIT_HYPERV_SYNIC 1
> > #define KVM_EXIT_HYPERV_HCALL 2
> > +#define KVM_EXIT_HYPERV_SYNDBG 3
> > __u32 type;
> > union {
> > struct {
> > @@ -201,6 +202,14 @@ struct kvm_hyperv_exit {
> > __u64 result;
> > __u64 params[2];
> > } hcall;
> > + struct {
> > + __u32 msr;
> > + __u64 control;
> > + __u64 status;
> > + __u64 send_page;
> > + __u64 recv_page;
> > + __u64 pending_page;
> > + } syndbg;
> > } u;
> > };
>
> Not your fault but I just noticed that 'struct kvm_hyperv_exit' is not
> properly padded. 'synic' struct is OK, however, 'hcall' is not as
> there's gonna be a gap between '__u32 type' and it. Your 'struct syndbg'
> is also OK as it starts with '__u32 msr' but we should do something
> about hcall.
>
Created another patch to address this.
> --
> Vitaly
>
Cheers,
-- Jon.
