Re: [Qemu-devel] [PATCH v3 9/9] kvm/x86: Hyper-V kvm exit

[Paolo Bonzini <pbonzini@redhat.com>]

On 22/10/2015 18:10, Andrey Smetanin wrote:
> A new vcpu exit is introduced to notify the userspace of the
> changes in Hyper-V SynIC configuration triggered by guest writing to the
> corresponding MSRs.
> 
> Changes v3:
> * added KVM_EXIT_HYPERV types and structs notes into docs
> 
> Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
> Reviewed-by: Roman Kagan <rkagan@virtiozzo.com>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Vitaly Kuznetsov <vkuznets@redhat.com>
> CC: "K. Y. Srinivasan" <kys@microsoft.com>
> CC: Gleb Natapov <gleb@kernel.org>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Roman Kagan <rkagan@virtiozzo.com>
> 
> ---
>  Documentation/virtual/kvm/api.txt | 22 ++++++++++++++++++++++
>  arch/x86/include/asm/kvm_host.h   |  1 +
>  arch/x86/kvm/hyperv.c             | 17 +++++++++++++++++
>  arch/x86/kvm/x86.c                |  6 ++++++
>  include/linux/kvm_host.h          |  1 +
>  include/uapi/linux/kvm.h          | 17 +++++++++++++++++
>  6 files changed, 64 insertions(+)
> 
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 8710418..a6858eb 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -3337,6 +3337,28 @@ the userspace IOAPIC should process the EOI and retrigger the interrupt if
>  it is still asserted.  Vector is the LAPIC interrupt vector for which the
>  EOI was received.
>  
> +		struct kvm_hyperv_exit {
> +#define KVM_EXIT_HYPERV_SYNIC          1
> +			__u32 type;
> +			union {
> +				struct {
> +					__u32 msr;
> +					__u64 control;
> +					__u64 evt_page;
> +					__u64 msg_page;
> +				} synic;
> +			} u;
> +		};
> +		/* KVM_EXIT_HYPERV */
> +                struct kvm_hyperv_exit hyperv;
> +Indicates that the VCPU exits into userspace to process some tasks
> +related to Hyper-V emulation.
> +Valid values for 'type' are:
> +	KVM_EXIT_HYPERV_SYNIC -- synchronously notify user-space about
> +Hyper-V SynIC state change. Notification is used to remap SynIC
> +event/message pages and to enable/disable SynIC messages/events processing
> +in userspace.
> +
>  		/* Fix the size of the union. */
>  		char padding[256];
>  	};
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 8434f88..54c90d3 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -392,6 +392,7 @@ struct kvm_vcpu_hv {
>  	u64 hv_vapic;
>  	s64 runtime_offset;
>  	struct kvm_vcpu_hv_synic synic;
> +	struct kvm_hyperv_exit exit;
>  };
>  
>  struct kvm_vcpu_arch {
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index 8ff71f3..9443920 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -129,6 +129,20 @@ static void kvm_hv_notify_acked_sint(struct kvm_vcpu *vcpu, u32 sint)
>  	srcu_read_unlock(&kvm->irq_srcu, idx);
>  }
>  
> +static void synic_exit(struct kvm_vcpu_hv_synic *synic, u32 msr)
> +{
> +	struct kvm_vcpu *vcpu = synic_to_vcpu(synic);
> +	struct kvm_vcpu_hv *hv_vcpu = &vcpu->arch.hyperv;
> +
> +	hv_vcpu->exit.type = KVM_EXIT_HYPERV_SYNIC;
> +	hv_vcpu->exit.u.synic.msr = msr;
> +	hv_vcpu->exit.u.synic.control = synic->control;
> +	hv_vcpu->exit.u.synic.evt_page = synic->evt_page;
> +	hv_vcpu->exit.u.synic.msg_page = synic->msg_page;
> +
> +	kvm_make_request(KVM_REQ_HV_EXIT, vcpu);
> +}
> +
>  static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
>  			 u32 msr, u64 data, bool host)
>  {
> @@ -141,6 +155,7 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
>  	switch (msr) {
>  	case HV_X64_MSR_SCONTROL:
>  		synic->control = data;
> +		synic_exit(synic, msr);

Another note.  I am getting:

EAX=00000000 EBX=00000000 ECX=00000000 EDX=00000663
ESI=00000000 EDI=00000000 EBP=00000000 ESP=00000000
EIP=0000fff0 EFL=00000002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0000 00000000 0000ffff 00009300
CS =f000 ffff0000 0000ffff 00009b00
SS =0000 00000000 0000ffff 00009300
DS =0000 00000000 0000ffff 00009300
FS =0000 00000000 0000ffff 00009300
GS =0000 00000000 0000ffff 00009300
LDT=0000 00000000 0000ffff 00008200
TR =0000 00000000 0000ffff 00008b00
GDT=     00000000 0000ffff
IDT=     00000000 0000ffff
CR0=60000010 CR2=00000000 CR3=00000000 CR4=00000000
DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000
DR3=0000000000000000
DR6=00000000ffff0ff0 DR7=0000000000000400
EFER=0000000000000000
Code=90 90 90 90 eb c3 90 90 90 90 90 90 00 00 00 00 56 54 46 00 <90> 90
eb ac 90 90 90 90 90 90 90 90 90 90 90 90 00 00 00 00 00 00 00 00 00 00
00 00 00 00

if I run a patched QEMU but I *do not* enable the synthetic interrupt
controller.  I can fix it by wrapping the calls to synic_exit with "if
(!host)", but I haven't checked yet the source---so that may not be the
proper fix.  Sorry for not having looked more in detail.

Paolo

>  		break;
>  	case HV_X64_MSR_SVERSION:
>  		if (!host) {
> @@ -157,6 +172,7 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
>  				break;
>  			}
>  		synic->evt_page = data;
> +		synic_exit(synic, msr);
>  		break;
>  	case HV_X64_MSR_SIMP:
>  		if (data & HV_SYNIC_SIMP_ENABLE)
> @@ -166,6 +182,7 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
>  				break;
>  			}
>  		synic->msg_page = data;
> +		synic_exit(synic, msr);
>  		break;
>  	case HV_X64_MSR_EOM: {
>  		int i;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index b853b2df..0704ee3 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6342,6 +6342,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>  			r = 0;
>  			goto out;
>  		}
> +		if (kvm_check_request(KVM_REQ_HV_EXIT, vcpu)) {
> +			vcpu->run->exit_reason = KVM_EXIT_HYPERV;
> +			vcpu->run->hyperv = vcpu->arch.hyperv.exit;
> +			r = 0;
> +			goto out;
> +		}
>  	}
>  
>  	/*
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 43b0141..e38ac16 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -143,6 +143,7 @@ static inline bool is_error_page(struct page *page)
>  #define KVM_REQ_HV_CRASH          27
>  #define KVM_REQ_IOAPIC_EOI_EXIT   28
>  #define KVM_REQ_HV_RESET          29
> +#define KVM_REQ_HV_EXIT           30
>  
>  #define KVM_USERSPACE_IRQ_SOURCE_ID		0
>  #define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID	1
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 27ce460..6e32f75 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -154,6 +154,20 @@ struct kvm_s390_skeys {
>  	__u32 flags;
>  	__u32 reserved[9];
>  };
> +
> +struct kvm_hyperv_exit {
> +#define KVM_EXIT_HYPERV_SYNIC          1
> +	__u32 type;
> +	union {
> +		struct {
> +			__u32 msr;
> +			__u64 control;
> +			__u64 evt_page;
> +			__u64 msg_page;
> +		} synic;
> +	} u;
> +};
> +
>  #define KVM_S390_GET_SKEYS_NONE   1
>  #define KVM_S390_SKEYS_MAX        1048576
>  
> @@ -184,6 +198,7 @@ struct kvm_s390_skeys {
>  #define KVM_EXIT_SYSTEM_EVENT     24
>  #define KVM_EXIT_S390_STSI        25
>  #define KVM_EXIT_IOAPIC_EOI       26
> +#define KVM_EXIT_HYPERV           27
>  
>  /* For KVM_EXIT_INTERNAL_ERROR */
>  /* Emulate instruction failed. */
> @@ -338,6 +353,8 @@ struct kvm_run {
>  		struct {
>  			__u8 vector;
>  		} eoi;
> +		/* KVM_EXIT_HYPERV */
> +		struct kvm_hyperv_exit hyperv;
>  		/* Fix the size of the union. */
>  		char padding[256];
>  	};
>