Re: [PATCH v5 2/5] x86/hyper-v: Add synthetic debugger definitions

[Jon Doron <arilou@gmail.com>]

On 13/03/2020, Michael Kelley wrote:
>From: Jon Doron <arilou@gmail.com> Sent: Friday, March 13, 2020 6:21 AM
>>
>> Hyper-V synthetic debugger has two modes, one that uses MSRs and
>> the other that use Hypercalls.
>>
>> Add all the required definitions to both types of synthetic debugger
>> interface.
>>
>> Some of the required new CPUIDs and MSRs are not documented in the TLFS
>> so they are in hyperv.h instead.
>>
>> Signed-off-by: Jon Doron <arilou@gmail.com>
>> ---
>>  arch/x86/include/asm/hyperv-tlfs.h |  6 ++++++
>>  arch/x86/kvm/hyperv.h              | 22 ++++++++++++++++++++++
>>  2 files changed, 28 insertions(+)
>>
>> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
>> index 92abc1e42bfc..671ce2a39d4b 100644
>> --- a/arch/x86/include/asm/hyperv-tlfs.h
>> +++ b/arch/x86/include/asm/hyperv-tlfs.h
>> @@ -131,6 +131,8 @@
>>  #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)
>>
>> @@ -376,6 +378,9 @@ struct hv_tsc_emulation_status {
>>  #define HVCALL_SEND_IPI_EX			0x0015
>>  #define HVCALL_POST_MESSAGE			0x005c
>>  #define HVCALL_SIGNAL_EVENT			0x005d
>> +#define HVCALL_POST_DEBUG_DATA			0x0069
>> +#define HVCALL_RETRIEVE_DEBUG_DATA		0x006a
>> +#define HVCALL_RESET_DEBUG_SESSION		0x006b
>>  #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE 0x00af
>>  #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST 0x00b0
>>
>> @@ -419,6 +424,7 @@ enum HV_GENERIC_SET_FORMAT {
>>  #define HV_STATUS_INVALID_HYPERCALL_INPUT	3
>>  #define HV_STATUS_INVALID_ALIGNMENT		4
>>  #define HV_STATUS_INVALID_PARAMETER		5
>> +#define HV_STATUS_OPERATION_DENIED		8
>>  #define HV_STATUS_INSUFFICIENT_MEMORY		11
>>  #define HV_STATUS_INVALID_PORT_ID		17
>>  #define HV_STATUS_INVALID_CONNECTION_ID		18
>> diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
>> index 757cb578101c..56bc3416b62f 100644
>> --- a/arch/x86/kvm/hyperv.h
>> +++ b/arch/x86/kvm/hyperv.h
>> @@ -23,6 +23,28 @@
>>
>>  #include <linux/kvm_host.h>
>>
>> +/* These defines are required by KDNet and they are not part of Hyper-V TLFS */
>
>I'm looking for a bit more info in the comment so that it's clear that the
>synthetic debugger functionality is not committed to be available going
>forward. Perhaps something along the lines of:
>
>/* The #defines related to the synthetic debugger are required by KDNet, but
> * they are not documented in the Hyper-V TLFS because the synthetic debugger
> * functionality has been deprecated and is subject to removal in future versions
> * of Windows.
> */
>
>But with that additional comment text,
>
>Reviewed-by: Michael Kelley <mikelley@microsoft.com>
>

Sure thing, but one quick question I have noticed that in the 6.0 TLFS 
the bit indicating the DEBUG_MSRS are available is still documented is 
that intentional or a juss a miss?

Cheers,
-- Jon.

>> +#define HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS	0x40000080
>> +#define HYPERV_CPUID_SYNDBG_INTERFACE			0x40000081
>> +#define HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES	0x40000082
>> +
>> +/*
>> + * Hyper-V synthetic debugger platform capabilities
>> + * These are HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES.EAX bits.
>> + */
>> +#define HV_X64_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING	BIT(1)
>> +
>> +/* 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 HV_X64_MSR_SYNDBG_OPTIONS bits */
>> +#define HV_X64_SYNDBG_OPTION_USE_HCALLS		BIT(2)
>> +
>>  static inline struct kvm_vcpu_hv *vcpu_to_hv_vcpu(struct kvm_vcpu *vcpu)
>>  {
>>  	return &vcpu->arch.hyperv;
>> --
>> 2.24.1
>