From: Roman Kagan <rkagan@virtuozzo.com>

Date: Fri, 14 Jul 2017 17:13:20 +0300

Subject: kvm: x86: hyperv: make VP_INDEX managed by userspace

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Patch-mainline: v4.13-rc1

Git-commit: d3457c877b14aaee8c52923eedf05a3b78af0476

References: bsc#1077761

Hyper-V identifies vCPUs by Virtual Processor Index, which can be

queried via HV_X64_MSR_VP_INDEX msr.  It is defined by the spec as a

sequential number which can't exceed the maximum number of vCPUs per VM.

APIC ids can be sparse and thus aren't a valid replacement for VP

indices.

Current KVM uses its internal vcpu index as VP_INDEX.  However, to make

it predictable and persistent across VM migrations, the userspace has to

control the value of VP_INDEX.

This patch achieves that, by storing vp_index explicitly on vcpu, and

allowing HV_X64_MSR_VP_INDEX to be set from the host side.  For

compatibility it's initialized to KVM vcpu index.  Also a few variables

are renamed to make clear distinction betweed this Hyper-V vp_index and

KVM vcpu_id (== APIC id).  Besides, a new capability,

KVM_CAP_HYPERV_VP_INDEX, is added to allow the userspace to skip

attempting msr writes where unsupported, to avoid spamming error logs.

Signed-off-by: Roman Kagan <rkagan@virtuozzo.com>

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

Acked-by: Alexander Graf <agraf@suse.de>

---

 Documentation/virtual/kvm/api.txt |    9 ++++++

 arch/x86/include/asm/kvm_host.h   |    1 

 arch/x86/kvm/hyperv.c             |   54 ++++++++++++++++++++++++--------------

 arch/x86/kvm/hyperv.h             |    1 

 arch/x86/kvm/x86.c                |    3 ++

 include/uapi/linux/kvm.h          |    1 

 6 files changed, 50 insertions(+), 19 deletions(-)

--- a/Documentation/virtual/kvm/api.txt

+++ b/Documentation/virtual/kvm/api.txt

@@ -4338,3 +4338,12 @@

 controller (SynIC).  The only difference with KVM_CAP_HYPERV_SYNIC is that KVM

 doesn't clear SynIC message and event flags pages when they are enabled by

 writing to the respective MSRs.

+

+8.12 KVM_CAP_HYPERV_VP_INDEX

+

+Architectures: x86

+

+This capability indicates that userspace can load HV_X64_MSR_VP_INDEX msr.  Its

+value is used to denote the target vcpu for a SynIC interrupt.  For

+compatibilty, KVM initializes this msr to KVM's internal vcpu index.  When this

+capability is absent, userspace can still query this msr's value.

--- a/arch/x86/include/asm/kvm_host.h

+++ b/arch/x86/include/asm/kvm_host.h

@@ -467,6 +467,7 @@

 /* Hyper-V per vcpu emulation context */

 struct kvm_vcpu_hv {

+	u32 vp_index;

 	u64 hv_vapic;

 	s64 runtime_offset;

 	struct kvm_vcpu_hv_synic synic;

--- a/arch/x86/kvm/hyperv.c

+++ b/arch/x86/kvm/hyperv.c

@@ -106,14 +106,27 @@

 	return 0;

 }

-static struct kvm_vcpu_hv_synic *synic_get(struct kvm *kvm, u32 vcpu_id)

+static struct kvm_vcpu *get_vcpu_by_vpidx(struct kvm *kvm, u32 vpidx)

+{

+	struct kvm_vcpu *vcpu = NULL;

+	int i;

+

+	if (vpidx < KVM_MAX_VCPUS)

+		vcpu = kvm_get_vcpu(kvm, vpidx);

+	if (vcpu && vcpu_to_hv_vcpu(vcpu)->vp_index == vpidx)

+		return vcpu;

+	kvm_for_each_vcpu(i, vcpu, kvm)

+		if (vcpu_to_hv_vcpu(vcpu)->vp_index == vpidx)

+			return vcpu;

+	return NULL;

+}

+

+static struct kvm_vcpu_hv_synic *synic_get(struct kvm *kvm, u32 vpidx)

 {

 	struct kvm_vcpu *vcpu;

 	struct kvm_vcpu_hv_synic *synic;

-	if (vcpu_id >= atomic_read(&kvm->online_vcpus))

-		return NULL;

-	vcpu = kvm_get_vcpu(kvm, vcpu_id);

+	vcpu = get_vcpu_by_vpidx(kvm, vpidx);

 	if (!vcpu)

 		return NULL;

 	synic = vcpu_to_synic(vcpu);

@@ -320,11 +333,11 @@

 	return ret;

 }

-int kvm_hv_synic_set_irq(struct kvm *kvm, u32 vcpu_id, u32 sint)

+int kvm_hv_synic_set_irq(struct kvm *kvm, u32 vpidx, u32 sint)

 {

 	struct kvm_vcpu_hv_synic *synic;

-	synic = synic_get(kvm, vcpu_id);

+	synic = synic_get(kvm, vpidx);

 	if (!synic)

 		return -EINVAL;

@@ -343,11 +356,11 @@

 			kvm_hv_notify_acked_sint(vcpu, i);

 }

-static int kvm_hv_set_sint_gsi(struct kvm *kvm, u32 vcpu_id, u32 sint, int gsi)

+static int kvm_hv_set_sint_gsi(struct kvm *kvm, u32 vpidx, u32 sint, int gsi)

 {

 	struct kvm_vcpu_hv_synic *synic;

-	synic = synic_get(kvm, vcpu_id);

+	synic = synic_get(kvm, vpidx);

 	if (!synic)

 		return -EINVAL;

@@ -689,6 +702,13 @@

 		stimer_init(&hv_vcpu->stimer[i], i);

 }

+void kvm_hv_vcpu_postcreate(struct kvm_vcpu *vcpu)

+{

+	struct kvm_vcpu_hv *hv_vcpu = vcpu_to_hv_vcpu(vcpu);

+

+	hv_vcpu->vp_index = kvm_vcpu_get_idx(vcpu);

+}

+

 int kvm_hv_activate_synic(struct kvm_vcpu *vcpu, bool dont_zero_synic_pages)

 {

 	struct kvm_vcpu_hv_synic *synic = vcpu_to_synic(vcpu);

@@ -983,6 +1003,11 @@

 	struct kvm_vcpu_hv *hv = &vcpu->arch.hyperv;

 	switch (msr) {

+	case HV_X64_MSR_VP_INDEX:

+		if (!host)

+			return 1;

+		hv->vp_index = (u32)data;

+		break;

 	case HV_X64_MSR_APIC_ASSIST_PAGE: {

 		u64 gfn;

 		unsigned long addr;

@@ -1094,18 +1119,9 @@

 	struct kvm_vcpu_hv *hv = &vcpu->arch.hyperv;

 	switch (msr) {

-	case HV_X64_MSR_VP_INDEX: {

-		int r;

-		struct kvm_vcpu *v;

-

-		kvm_for_each_vcpu(r, v, vcpu->kvm) {

-			if (v == vcpu) {

-				data = r;

-				break;

-			}

-		}

+	case HV_X64_MSR_VP_INDEX:

+		data = hv->vp_index;

 		break;

-	}

 	case HV_X64_MSR_EOI:

 		return kvm_hv_vapic_msr_read(vcpu, APIC_EOI, pdata);

 	case HV_X64_MSR_ICR:

--- a/arch/x86/kvm/hyperv.h

+++ b/arch/x86/kvm/hyperv.h

@@ -59,6 +59,7 @@

 int kvm_hv_activate_synic(struct kvm_vcpu *vcpu, bool dont_zero_synic_pages);

 void kvm_hv_vcpu_init(struct kvm_vcpu *vcpu);

+void kvm_hv_vcpu_postcreate(struct kvm_vcpu *vcpu);

 void kvm_hv_vcpu_uninit(struct kvm_vcpu *vcpu);

 static inline struct kvm_vcpu_hv_stimer *vcpu_to_stimer(struct kvm_vcpu *vcpu,

--- a/arch/x86/kvm/x86.c

+++ b/arch/x86/kvm/x86.c

@@ -2667,6 +2667,7 @@

 	case KVM_CAP_HYPERV_SPIN:

 	case KVM_CAP_HYPERV_SYNIC:

 	case KVM_CAP_HYPERV_SYNIC2:

+	case KVM_CAP_HYPERV_VP_INDEX:

 	case KVM_CAP_PCI_SEGMENT:

 	case KVM_CAP_DEBUGREGS:

 	case KVM_CAP_X86_ROBUST_SINGLESTEP:

@@ -7700,6 +7701,8 @@

 	struct msr_data msr;

 	struct kvm *kvm = vcpu->kvm;

+	kvm_hv_vcpu_postcreate(vcpu);

+

 	if (vcpu_load(vcpu))

 		return;

 	msr.data = 0x0;

--- a/include/uapi/linux/kvm.h

+++ b/include/uapi/linux/kvm.h

@@ -929,6 +929,7 @@

 #define KVM_CAP_PPC_FWNMI 146

 #define KVM_CAP_PPC_SMT_POSSIBLE 147

 #define KVM_CAP_HYPERV_SYNIC2 148

+#define KVM_CAP_HYPERV_VP_INDEX 149

 #ifdef KVM_CAP_IRQ_ROUTING