Re: [RFC PATCH v3 1/2] add support for Hyper-V reference time counter

[Peter Lieven <pl@dlhnet.de>]

Am 11.12.2013 19:53, schrieb Marcelo Tosatti:
> On Sun, Dec 08, 2013 at 10:33:38PM +1100, Vadim Rozenfeld wrote:
>> Signed-off: Peter Lieven <pl@dlh.net>
>> Signed-off: Gleb Natapov <gleb@redhat.com>
>> Signed-off: Vadim Rozenfeld <vrozenfe@redhat.com>
>>
>> v1 -> v2
>> 1. mark TSC page dirty as suggested by 
>>     Eric Northup <digitaleric@google.com> and Gleb
>> 2. disable local irq when calling get_kernel_ns, 
>>     as it was done by Peter Lieven <pl@dlhnet.de>
>> 3. move check for TSC page enable from second patch
>>     to this one.
>>
>> ---
>>  arch/x86/include/asm/kvm_host.h    |  2 ++
>>  arch/x86/include/uapi/asm/hyperv.h | 13 +++++++++++++
>>  arch/x86/kvm/x86.c                 | 39 +++++++++++++++++++++++++++++++++++++-
>>  include/uapi/linux/kvm.h           |  1 +
>>  4 files changed, 54 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>> index ae5d783..2fd0753 100644
>> --- a/arch/x86/include/asm/kvm_host.h
>> +++ b/arch/x86/include/asm/kvm_host.h
>> @@ -605,6 +605,8 @@ struct kvm_arch {
>>  	/* fields used by HYPER-V emulation */
>>  	u64 hv_guest_os_id;
>>  	u64 hv_hypercall;
>> +	u64 hv_ref_count;
>> +	u64 hv_tsc_page;
>>  
>>  	#ifdef CONFIG_KVM_MMU_AUDIT
>>  	int audit_point;
>> diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
>> index b8f1c01..462efe7 100644
>> --- a/arch/x86/include/uapi/asm/hyperv.h
>> +++ b/arch/x86/include/uapi/asm/hyperv.h
>> @@ -28,6 +28,9 @@
>>  /* Partition Reference Counter (HV_X64_MSR_TIME_REF_COUNT) available*/
>>  #define HV_X64_MSR_TIME_REF_COUNT_AVAILABLE	(1 << 1)
>>  
>> +/* A partition's reference time stamp counter (TSC) page */
>> +#define HV_X64_MSR_REFERENCE_TSC		0x40000021
>> +
>>  /*
>>   * There is a single feature flag that signifies the presence of the MSR
>>   * that can be used to retrieve both the local APIC Timer frequency as
>> @@ -198,6 +201,9 @@
>>  #define HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_MASK	\
>>  		(~((1ull << HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT) - 1))
>>  
>> +#define HV_X64_MSR_TSC_REFERENCE_ENABLE		0x00000001
>> +#define HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT	12
>> +
>>  #define HV_PROCESSOR_POWER_STATE_C0		0
>>  #define HV_PROCESSOR_POWER_STATE_C1		1
>>  #define HV_PROCESSOR_POWER_STATE_C2		2
>> @@ -210,4 +216,11 @@
>>  #define HV_STATUS_INVALID_ALIGNMENT		4
>>  #define HV_STATUS_INSUFFICIENT_BUFFERS		19
>>  
>> +typedef struct _HV_REFERENCE_TSC_PAGE {
>> +	__u32 tsc_sequence;
>> +	__u32 res1;
>> +	__u64 tsc_scale;
>> +	__s64 tsc_offset;
>> +} HV_REFERENCE_TSC_PAGE, *PHV_REFERENCE_TSC_PAGE;
>> +
>>  #endif
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 21ef1ba..5e4e495a 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -840,7 +840,7 @@ EXPORT_SYMBOL_GPL(kvm_rdpmc);
>>  static u32 msrs_to_save[] = {
>>  	MSR_KVM_SYSTEM_TIME, MSR_KVM_WALL_CLOCK,
>>  	MSR_KVM_SYSTEM_TIME_NEW, MSR_KVM_WALL_CLOCK_NEW,
>> -	HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL,
>> +	HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL, HV_X64_MSR_TIME_REF_COUNT,
>>  	HV_X64_MSR_APIC_ASSIST_PAGE, MSR_KVM_ASYNC_PF_EN, MSR_KVM_STEAL_TIME,
>>  	MSR_KVM_PV_EOI_EN,
>>  	MSR_IA32_SYSENTER_CS, MSR_IA32_SYSENTER_ESP, MSR_IA32_SYSENTER_EIP,
>> @@ -1826,6 +1826,8 @@ static bool kvm_hv_msr_partition_wide(u32 msr)
>>  	switch (msr) {
>>  	case HV_X64_MSR_GUEST_OS_ID:
>>  	case HV_X64_MSR_HYPERCALL:
>> +	case HV_X64_MSR_REFERENCE_TSC:
>> +	case HV_X64_MSR_TIME_REF_COUNT:
>>  		r = true;
>>  		break;
>>  	}
>> @@ -1865,6 +1867,29 @@ static int set_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data)
>>  		if (__copy_to_user((void __user *)addr, instructions, 4))
>>  			return 1;
>>  		kvm->arch.hv_hypercall = data;
>> +		local_irq_disable();
>> +		kvm->arch.hv_ref_count = get_kernel_ns() + kvm->arch.kvmclock_offset;
>> +		local_irq_enable();
> 
> Where does the docs say that HV_X64_MSR_HYPERCALL is the where the clock
> starts counting?
> 
> No need to store kvmclock_offset in hv_ref_count? (moreover
> the name is weird, better name would be "hv_ref_start_time".
> 
>> +		break;
>> +	}
>> +	case HV_X64_MSR_REFERENCE_TSC: {
>> +		u64 gfn;
>> +		unsigned long addr;
>> +		HV_REFERENCE_TSC_PAGE tsc_ref;
>> +		tsc_ref.tsc_sequence = 0;
>> +		if (!(data & HV_X64_MSR_TSC_REFERENCE_ENABLE)) {
>> +			kvm->arch.hv_tsc_page = data;
>> +			break;
>> +		}
>> +		gfn = data >> HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT;
>> +		addr = gfn_to_hva(kvm, data >>
>> +			HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT);
>> +		if (kvm_is_error_hva(addr))
>> +			return 1;
>> +		if (__copy_to_user((void __user *)addr, &tsc_ref, sizeof(tsc_ref)))
>> +			return 1;
>> +		mark_page_dirty(kvm, gfn);
>> +		kvm->arch.hv_tsc_page = data;
>>  		break;
>>  	}
>>  	default:
>> @@ -2291,6 +2316,17 @@ static int get_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
>>  	case HV_X64_MSR_HYPERCALL:
>>  		data = kvm->arch.hv_hypercall;
>>  		break;
>> +	case HV_X64_MSR_TIME_REF_COUNT: {
>> +		u64 now_ns;
>> +		local_irq_disable();
>> +		now_ns = get_kernel_ns() + kvm->arch.kvmclock_offset;
>> +		data = div_u64(now_ns - kvm->arch.hv_ref_count, 100);
>> +		local_irq_enable();
> 
> No need for irq disable/enable pairs.

KVM_GET_CLOCK / KVM_SET_CLOCK do the irq disable/enable pairs. What is right?

Peter