[PATCH v4 0/5] KVM: x86: hyperv: PV IPI support for Windows guests

[PATCH v4 0/5] KVM: x86: hyperv: PV IPI support for Windows guests

[Vitaly Kuznetsov]

Changes since v3 [Roman Kagan]:
- Don't use vcpu_id in kvm_make_vcpus_request_mask to avoid dealing with
  sparse CPU masks.
- Create get_vcpu_idx_by_vpidx() and use it in get_vcpu_by_vpidx() and
  kvm_hv_flush_tlb().

Using hypercall for sending IPIs is faster because this allows to specify
any number of vCPUs (even > 64 with sparse CPU set), the whole procedure
will take only one VMEXIT.

Same as PV TLB flush, this allows Windows guests having > 64 vCPUs to boot
on KVM when Hyper-V extensions are enabled.

Vitaly Kuznetsov (5):
  KVM: x86: hyperv: enforce vp_index < KVM_MAX_VCPUS
  KVM: x86: hyperv: optimize 'all cpus' case in kvm_hv_flush_tlb()
  KVM: x86: hyperv: use get_vcpu_by_vpidx() in kvm_hv_flush_tlb()
  x86/hyper-v: rename ipi_arg_{ex,non_ex} structures
  KVM: x86: hyperv: implement PV IPI send hypercalls

 Documentation/virtual/kvm/api.txt  |   8 ++
 arch/x86/hyperv/hv_apic.c          |  12 +--
 arch/x86/include/asm/hyperv-tlfs.h |  16 +--
 arch/x86/kvm/hyperv.c              | 211 +++++++++++++++++++++++++++----------
 arch/x86/kvm/trace.h               |  42 ++++++++
 arch/x86/kvm/x86.c                 |   1 +
 include/uapi/linux/kvm.h           |   1 +
 virt/kvm/kvm_main.c                |   6 +-
 8 files changed, 224 insertions(+), 73 deletions(-)

-- 
2.14.4

[PATCH v4 1/5] KVM: x86: hyperv: enforce vp_index < KVM_MAX_VCPUS

[Vitaly Kuznetsov]

Hyper-V TLFS (5.0b) states:

> Virtual processors are identified by using an index (VP index). The
> maximum number of virtual processors per partition supported by the
> current implementation of the hypervisor can be obtained through CPUID
> leaf 0x40000005. A virtual processor index must be less than the
> maximum number of virtual processors per partition.

Forbid userspace to set VP_INDEX above KVM_MAX_VCPUS. get_vcpu_by_vpidx()
can now be optimized to bail early when supplied vpidx is >= KVM_MAX_VCPUS.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 arch/x86/kvm/hyperv.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index af8caf965baa..ceaa7fb10c49 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -132,8 +132,10 @@ 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 (vpidx >= KVM_MAX_VCPUS)
+		return NULL;
+
+	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)
@@ -1038,7 +1040,7 @@ static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
 
 	switch (msr) {
 	case HV_X64_MSR_VP_INDEX:
-		if (!host)
+		if (!host || (u32)data >= KVM_MAX_VCPUS)
 			return 1;
 		hv->vp_index = (u32)data;
 		break;
-- 
2.14.4

Re: [PATCH v4 1/5] KVM: x86: hyperv: enforce vp_index < KVM_MAX_VCPUS

[Roman Kagan]

On Tue, Jul 03, 2018 at 03:42:02PM +0200, Vitaly Kuznetsov wrote:
> Hyper-V TLFS (5.0b) states:
> 
> > Virtual processors are identified by using an index (VP index). The
> > maximum number of virtual processors per partition supported by the
> > current implementation of the hypervisor can be obtained through CPUID
> > leaf 0x40000005. A virtual processor index must be less than the
> > maximum number of virtual processors per partition.
> 
> Forbid userspace to set VP_INDEX above KVM_MAX_VCPUS. get_vcpu_by_vpidx()
> can now be optimized to bail early when supplied vpidx is >= KVM_MAX_VCPUS.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  arch/x86/kvm/hyperv.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)

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

[PATCH v4 2/5] KVM: x86: hyperv: optimize 'all cpus' case in kvm_hv_flush_tlb()

[Vitaly Kuznetsov]

We can use 'NULL' to represent 'all cpus' case in
kvm_make_vcpus_request_mask() and avoid building vCPU mask with
all vCPUs.

Suggested-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 arch/x86/kvm/hyperv.c | 42 +++++++++++++++++++++++-------------------
 virt/kvm/kvm_main.c   |  6 ++----
 2 files changed, 25 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index ceaa7fb10c49..c5b921c0a467 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1312,35 +1312,39 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *current_vcpu, u64 ingpa,
 
 	cpumask_clear(&hv_current->tlb_lush);
 
+	if (all_cpus) {
+		kvm_make_vcpus_request_mask(kvm,
+				    KVM_REQ_TLB_FLUSH | KVM_REQUEST_NO_WAKEUP,
+				    NULL, &hv_current->tlb_lush);
+		goto ret_success;
+	}
+
 	kvm_for_each_vcpu(i, vcpu, kvm) {
 		struct kvm_vcpu_hv *hv = &vcpu->arch.hyperv;
 		int bank = hv->vp_index / 64, sbank = 0;
 
-		if (!all_cpus) {
-			/* Banks >64 can't be represented */
-			if (bank >= 64)
-				continue;
-
-			/* Non-ex hypercalls can only address first 64 vCPUs */
-			if (!ex && bank)
-				continue;
+		/* Banks >64 can't be represented */
+		if (bank >= 64)
+			continue;
 
-			if (ex) {
-				/*
-				 * Check is the bank of this vCPU is in sparse
-				 * set and get the sparse bank number.
-				 */
-				sbank = get_sparse_bank_no(valid_bank_mask,
-							   bank);
+		/* Non-ex hypercalls can only address first 64 vCPUs */
+		if (!ex && bank)
+			continue;
 
-				if (sbank < 0)
-					continue;
-			}
+		if (ex) {
+			/*
+			 * Check is the bank of this vCPU is in sparse
+			 * set and get the sparse bank number.
+			 */
+			sbank = get_sparse_bank_no(valid_bank_mask, bank);
 
-			if (!(sparse_banks[sbank] & BIT_ULL(hv->vp_index % 64)))
+			if (sbank < 0)
 				continue;
 		}
 
+		if (!(sparse_banks[sbank] & BIT_ULL(hv->vp_index % 64)))
+			continue;
+
 		/*
 		 * vcpu->arch.cr3 may not be up-to-date for running vCPUs so we
 		 * can't analyze it here, flush TLB regardless of the specified
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index ada21f47f22b..153f14e91fb1 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -213,7 +213,7 @@ bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req,
 	me = get_cpu();
 
 	kvm_for_each_vcpu(i, vcpu, kvm) {
-		if (!test_bit(i, vcpu_bitmap))
+		if (vcpu_bitmap && !test_bit(i, vcpu_bitmap))
 			continue;
 
 		kvm_make_request(req, vcpu);
@@ -237,12 +237,10 @@ bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
 {
 	cpumask_var_t cpus;
 	bool called;
-	static unsigned long vcpu_bitmap[BITS_TO_LONGS(KVM_MAX_VCPUS)]
-		= {[0 ... BITS_TO_LONGS(KVM_MAX_VCPUS)-1] = ULONG_MAX};
 
 	zalloc_cpumask_var(&cpus, GFP_ATOMIC);
 
-	called = kvm_make_vcpus_request_mask(kvm, req, vcpu_bitmap, cpus);
+	called = kvm_make_vcpus_request_mask(kvm, req, NULL, cpus);
 
 	free_cpumask_var(cpus);
 	return called;
-- 
2.14.4

Re: [PATCH v4 2/5] KVM: x86: hyperv: optimize 'all cpus' case in kvm_hv_flush_tlb()

[Roman Kagan]

On Tue, Jul 03, 2018 at 03:42:03PM +0200, Vitaly Kuznetsov wrote:
> We can use 'NULL' to represent 'all cpus' case in
> kvm_make_vcpus_request_mask() and avoid building vCPU mask with
> all vCPUs.
> 
> Suggested-by: Radim Krčmář <rkrcmar@redhat.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  arch/x86/kvm/hyperv.c | 42 +++++++++++++++++++++++-------------------
>  virt/kvm/kvm_main.c   |  6 ++----
>  2 files changed, 25 insertions(+), 23 deletions(-)

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

[PATCH v4 3/5] KVM: x86: hyperv: use get_vcpu_by_vpidx() in kvm_hv_flush_tlb()

[Vitaly Kuznetsov]

VP_INDEX almost always matches VCPU id and get_vcpu_by_vpidx() is fast,
use it instead of traversing full vCPU list every time.

To support the change split off get_vcpu_idx_by_vpidx() from
get_vcpu_by_vpidx().

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 arch/x86/kvm/hyperv.c | 78 ++++++++++++++++++++-------------------------------
 1 file changed, 31 insertions(+), 47 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index c5b921c0a467..8db20c9d4529 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -127,20 +127,31 @@ static int synic_set_sint(struct kvm_vcpu_hv_synic *synic, int sint,
 	return 0;
 }
 
-static struct kvm_vcpu *get_vcpu_by_vpidx(struct kvm *kvm, u32 vpidx)
+static u32 get_vcpu_idx_by_vpidx(struct kvm *kvm, u32 vpidx)
 {
 	struct kvm_vcpu *vcpu = NULL;
 	int i;
 
 	if (vpidx >= KVM_MAX_VCPUS)
-		return NULL;
+		return U32_MAX;
 
 	vcpu = kvm_get_vcpu(kvm, vpidx);
 	if (vcpu && vcpu_to_hv_vcpu(vcpu)->vp_index == vpidx)
-		return vcpu;
+		return vpidx;
 	kvm_for_each_vcpu(i, vcpu, kvm)
 		if (vcpu_to_hv_vcpu(vcpu)->vp_index == vpidx)
-			return vcpu;
+			return i;
+	return U32_MAX;
+}
+
+static __always_inline struct kvm_vcpu *get_vcpu_by_vpidx(struct kvm *kvm,
+							  u32 vpidx)
+{
+	u32 vcpu_idx = get_vcpu_idx_by_vpidx(kvm, vpidx);
+
+	if (vcpu_idx < KVM_MAX_VCPUS)
+		return kvm_get_vcpu(kvm, vcpu_idx);
+
 	return NULL;
 }
 
@@ -1244,20 +1255,6 @@ int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 		return kvm_hv_get_msr(vcpu, msr, pdata);
 }
 
-static __always_inline int get_sparse_bank_no(u64 valid_bank_mask, int bank_no)
-{
-	int i = 0, j;
-
-	if (!(valid_bank_mask & BIT_ULL(bank_no)))
-		return -1;
-
-	for (j = 0; j < bank_no; j++)
-		if (valid_bank_mask & BIT_ULL(j))
-			i++;
-
-	return i;
-}
-
 static u64 kvm_hv_flush_tlb(struct kvm_vcpu *current_vcpu, u64 ingpa,
 			    u16 rep_cnt, bool ex)
 {
@@ -1265,11 +1262,10 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *current_vcpu, u64 ingpa,
 	struct kvm_vcpu_hv *hv_current = &current_vcpu->arch.hyperv;
 	struct hv_tlb_flush_ex flush_ex;
 	struct hv_tlb_flush flush;
-	struct kvm_vcpu *vcpu;
 	unsigned long vcpu_bitmap[BITS_TO_LONGS(KVM_MAX_VCPUS)] = {0};
-	unsigned long valid_bank_mask = 0;
+	unsigned long valid_bank_mask;
 	u64 sparse_banks[64];
-	int sparse_banks_len, i;
+	int sparse_banks_len, bank, i;
 	bool all_cpus;
 
 	if (!ex) {
@@ -1279,6 +1275,7 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *current_vcpu, u64 ingpa,
 		trace_kvm_hv_flush_tlb(flush.processor_mask,
 				       flush.address_space, flush.flags);
 
+		valid_bank_mask = BIT_ULL(0);
 		sparse_banks[0] = flush.processor_mask;
 		all_cpus = flush.flags & HV_FLUSH_ALL_PROCESSORS;
 	} else {
@@ -1319,38 +1316,25 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *current_vcpu, u64 ingpa,
 		goto ret_success;
 	}
 
-	kvm_for_each_vcpu(i, vcpu, kvm) {
-		struct kvm_vcpu_hv *hv = &vcpu->arch.hyperv;
-		int bank = hv->vp_index / 64, sbank = 0;
+	for_each_set_bit(bank, (unsigned long *)&valid_bank_mask,
+			 BITS_PER_LONG) {
 
-		/* Banks >64 can't be represented */
-		if (bank >= 64)
-			continue;
+		for_each_set_bit(i, (unsigned long *)&sparse_banks[bank],
+				 BITS_PER_LONG) {
+			u32 vp_index = bank * 64 + i;
+			u32 vcpu_idx = get_vcpu_idx_by_vpidx(kvm, vp_index);
 
-		/* Non-ex hypercalls can only address first 64 vCPUs */
-		if (!ex && bank)
-			continue;
+			/* A non-existent vCPU was specified */
+			if (vcpu_idx >= KVM_MAX_VCPUS)
+				return HV_STATUS_INVALID_HYPERCALL_INPUT;
 
-		if (ex) {
 			/*
-			 * Check is the bank of this vCPU is in sparse
-			 * set and get the sparse bank number.
+			 * vcpu->arch.cr3 may not be up-to-date for running
+			 * vCPUs so we can't analyze it here, flush TLB
+			 * regardless of the specified address space.
 			 */
-			sbank = get_sparse_bank_no(valid_bank_mask, bank);
-
-			if (sbank < 0)
-				continue;
+			__set_bit(vcpu_idx, vcpu_bitmap);
 		}
-
-		if (!(sparse_banks[sbank] & BIT_ULL(hv->vp_index % 64)))
-			continue;
-
-		/*
-		 * vcpu->arch.cr3 may not be up-to-date for running vCPUs so we
-		 * can't analyze it here, flush TLB regardless of the specified
-		 * address space.
-		 */
-		__set_bit(i, vcpu_bitmap);
 	}
 
 	kvm_make_vcpus_request_mask(kvm,
-- 
2.14.4

Re: [PATCH v4 3/5] KVM: x86: hyperv: use get_vcpu_by_vpidx() in kvm_hv_flush_tlb()

[Roman Kagan]

On Tue, Jul 03, 2018 at 03:42:04PM +0200, Vitaly Kuznetsov wrote:
> VP_INDEX almost always matches VCPU id and get_vcpu_by_vpidx() is fast,
> use it instead of traversing full vCPU list every time.
> 
> To support the change split off get_vcpu_idx_by_vpidx() from
> get_vcpu_by_vpidx().
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  arch/x86/kvm/hyperv.c | 78 ++++++++++++++++++++-------------------------------
>  1 file changed, 31 insertions(+), 47 deletions(-)

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

[PATCH v4 4/5] x86/hyper-v: rename ipi_arg_{ex,non_ex} structures

[Vitaly Kuznetsov]

These structures are going to be used from KVM code so let's make
their names reflect their Hyper-V origin.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 arch/x86/hyperv/hv_apic.c          | 12 ++++++------
 arch/x86/include/asm/hyperv-tlfs.h | 16 +++++++++-------
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
index f68855499391..cb17168e6263 100644
--- a/arch/x86/hyperv/hv_apic.c
+++ b/arch/x86/hyperv/hv_apic.c
@@ -93,14 +93,14 @@ static void hv_apic_eoi_write(u32 reg, u32 val)
  */
 static bool __send_ipi_mask_ex(const struct cpumask *mask, int vector)
 {
-	struct ipi_arg_ex **arg;
-	struct ipi_arg_ex *ipi_arg;
+	struct hv_send_ipi_ex **arg;
+	struct hv_send_ipi_ex *ipi_arg;
 	unsigned long flags;
 	int nr_bank = 0;
 	int ret = 1;
 
 	local_irq_save(flags);
-	arg = (struct ipi_arg_ex **)this_cpu_ptr(hyperv_pcpu_input_arg);
+	arg = (struct hv_send_ipi_ex **)this_cpu_ptr(hyperv_pcpu_input_arg);
 
 	ipi_arg = *arg;
 	if (unlikely(!ipi_arg))
@@ -128,8 +128,8 @@ static bool __send_ipi_mask_ex(const struct cpumask *mask, int vector)
 static bool __send_ipi_mask(const struct cpumask *mask, int vector)
 {
 	int cur_cpu, vcpu;
-	struct ipi_arg_non_ex **arg;
-	struct ipi_arg_non_ex *ipi_arg;
+	struct hv_send_ipi **arg;
+	struct hv_send_ipi *ipi_arg;
 	int ret = 1;
 	unsigned long flags;
 
@@ -146,7 +146,7 @@ static bool __send_ipi_mask(const struct cpumask *mask, int vector)
 		return __send_ipi_mask_ex(mask, vector);
 
 	local_irq_save(flags);
-	arg = (struct ipi_arg_non_ex **)this_cpu_ptr(hyperv_pcpu_input_arg);
+	arg = (struct hv_send_ipi **)this_cpu_ptr(hyperv_pcpu_input_arg);
 
 	ipi_arg = *arg;
 	if (unlikely(!ipi_arg))
diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index b8c89265baf0..b52c9604b20d 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -723,19 +723,21 @@ struct hv_enlightened_vmcs {
 #define HV_STIMER_AUTOENABLE		(1ULL << 3)
 #define HV_STIMER_SINT(config)		(__u8)(((config) >> 16) & 0x0F)
 
-struct ipi_arg_non_ex {
-	u32 vector;
-	u32 reserved;
-	u64 cpu_mask;
-};
-
 struct hv_vpset {
 	u64 format;
 	u64 valid_bank_mask;
 	u64 bank_contents[];
 };
 
-struct ipi_arg_ex {
+/* HvCallSendSyntheticClusterIpi hypercall */
+struct hv_send_ipi {
+	u32 vector;
+	u32 reserved;
+	u64 cpu_mask;
+};
+
+/* HvCallSendSyntheticClusterIpiEx hypercall */
+struct hv_send_ipi_ex {
 	u32 vector;
 	u32 reserved;
 	struct hv_vpset vp_set;
-- 
2.14.4

Re: [PATCH v4 4/5] x86/hyper-v: rename ipi_arg_{ex,non_ex} structures

[Roman Kagan]

On Tue, Jul 03, 2018 at 03:42:05PM +0200, Vitaly Kuznetsov wrote:
> These structures are going to be used from KVM code so let's make
> their names reflect their Hyper-V origin.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  arch/x86/hyperv/hv_apic.c          | 12 ++++++------
>  arch/x86/include/asm/hyperv-tlfs.h | 16 +++++++++-------
>  2 files changed, 15 insertions(+), 13 deletions(-)

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

[PATCH v4 5/5] KVM: x86: hyperv: implement PV IPI send hypercalls

[Vitaly Kuznetsov]

Using hypercall for sending IPIs is faster because this allows to specify
any number of vCPUs (even > 64 with sparse CPU set), the whole procedure
will take only one VMEXIT.

Current Hyper-V TLFS (v5.0b) claims that HvCallSendSyntheticClusterIpi
hypercall can't be 'fast' (passing parameters through registers) but
apparently this is not true, Windows always uses it as 'fast' so we need
to support that.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 Documentation/virtual/kvm/api.txt |   8 +++
 arch/x86/kvm/hyperv.c             | 109 ++++++++++++++++++++++++++++++++++++++
 arch/x86/kvm/trace.h              |  42 +++++++++++++++
 arch/x86/kvm/x86.c                |   1 +
 include/uapi/linux/kvm.h          |   1 +
 5 files changed, 161 insertions(+)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 495b7742ab58..1f3a9ea6a59c 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -4618,3 +4618,11 @@ This capability indicates that KVM supports paravirtualized Hyper-V TLB Flush
 hypercalls:
 HvFlushVirtualAddressSpace, HvFlushVirtualAddressSpaceEx,
 HvFlushVirtualAddressList, HvFlushVirtualAddressListEx.
+
+8.19 KVM_CAP_HYPERV_SEND_IPI
+
+Architectures: x86
+
+This capability indicates that KVM supports paravirtualized Hyper-V IPI send
+hypercalls:
+HvCallSendSyntheticClusterIpi, HvCallSendSyntheticClusterIpiEx.
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 8db20c9d4529..4edfaaf6ad91 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1347,6 +1347,101 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *current_vcpu, u64 ingpa,
 		((u64)rep_cnt << HV_HYPERCALL_REP_COMP_OFFSET);
 }
 
+static u64 kvm_hv_send_ipi(struct kvm_vcpu *current_vcpu, u64 ingpa, u64 outgpa,
+			   bool ex, bool fast)
+{
+	struct kvm *kvm = current_vcpu->kvm;
+	struct hv_send_ipi_ex send_ipi_ex;
+	struct hv_send_ipi send_ipi;
+	struct kvm_vcpu *vcpu;
+	unsigned long valid_bank_mask;
+	u64 sparse_banks[64];
+	int sparse_banks_len, bank, i;
+	struct kvm_lapic_irq irq = {.delivery_mode = APIC_DM_FIXED};
+	bool all_cpus;
+
+	if (!ex) {
+		if (!fast) {
+			if (unlikely(kvm_read_guest(kvm, ingpa, &send_ipi,
+						    sizeof(send_ipi))))
+				return HV_STATUS_INVALID_HYPERCALL_INPUT;
+			sparse_banks[0] = send_ipi.cpu_mask;
+			irq.vector = send_ipi.vector;
+		} else {
+			/* 'reserved' part of hv_send_ipi should be 0 */
+			if (unlikely(ingpa >> 32 != 0))
+				return HV_STATUS_INVALID_HYPERCALL_INPUT;
+			sparse_banks[0] = outgpa;
+			irq.vector = (u32)ingpa;
+		}
+		all_cpus = false;
+		valid_bank_mask = BIT_ULL(0);
+
+		trace_kvm_hv_send_ipi(irq.vector, sparse_banks[0]);
+	} else {
+		if (unlikely(kvm_read_guest(kvm, ingpa, &send_ipi_ex,
+					    sizeof(send_ipi_ex))))
+			return HV_STATUS_INVALID_HYPERCALL_INPUT;
+
+		trace_kvm_hv_send_ipi_ex(send_ipi_ex.vector,
+					 send_ipi_ex.vp_set.format,
+					 send_ipi_ex.vp_set.valid_bank_mask);
+
+		irq.vector = send_ipi_ex.vector;
+		valid_bank_mask = send_ipi_ex.vp_set.valid_bank_mask;
+		sparse_banks_len = bitmap_weight(&valid_bank_mask, 64) *
+			sizeof(sparse_banks[0]);
+
+		all_cpus = send_ipi_ex.vp_set.format == HV_GENERIC_SET_ALL;
+
+		if (!sparse_banks_len)
+			goto ret_success;
+
+		if (!all_cpus &&
+		    kvm_read_guest(kvm,
+				   ingpa + offsetof(struct hv_send_ipi_ex,
+						    vp_set.bank_contents),
+				   sparse_banks,
+				   sparse_banks_len))
+			return HV_STATUS_INVALID_HYPERCALL_INPUT;
+	}
+
+	if ((irq.vector < HV_IPI_LOW_VECTOR) ||
+	    (irq.vector > HV_IPI_HIGH_VECTOR))
+		return HV_STATUS_INVALID_HYPERCALL_INPUT;
+
+	if (all_cpus) {
+		kvm_for_each_vcpu(i, vcpu, kvm) {
+			/* We fail only when APIC is disabled */
+			if (!kvm_apic_set_irq(vcpu, &irq, NULL))
+				return HV_STATUS_INVALID_HYPERCALL_INPUT;
+		}
+		goto ret_success;
+	}
+
+	for_each_set_bit(bank, (unsigned long *)&valid_bank_mask,
+			 BITS_PER_LONG) {
+
+		for_each_set_bit(i, (unsigned long *)&sparse_banks[bank],
+				 BITS_PER_LONG) {
+			u32 vp_index = bank * 64 + i;
+			struct kvm_vcpu *vcpu =
+				get_vcpu_by_vpidx(kvm, vp_index);
+
+			/* Unknown vCPU specified */
+			if (!vcpu)
+				return HV_STATUS_INVALID_HYPERCALL_INPUT;
+
+			/* We fail only when APIC is disabled */
+			if (!kvm_apic_set_irq(vcpu, &irq, NULL))
+				return HV_STATUS_INVALID_HYPERCALL_INPUT;
+		}
+	}
+
+ret_success:
+	return HV_STATUS_SUCCESS;
+}
+
 bool kvm_hv_hypercall_enabled(struct kvm *kvm)
 {
 	return READ_ONCE(kvm->arch.hyperv.hv_hypercall) & HV_X64_MSR_HYPERCALL_ENABLE;
@@ -1516,6 +1611,20 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 		}
 		ret = kvm_hv_flush_tlb(vcpu, ingpa, rep_cnt, true);
 		break;
+	case HVCALL_SEND_IPI:
+		if (unlikely(rep)) {
+			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
+			break;
+		}
+		ret = kvm_hv_send_ipi(vcpu, ingpa, outgpa, false, fast);
+		break;
+	case HVCALL_SEND_IPI_EX:
+		if (unlikely(fast || rep)) {
+			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
+			break;
+		}
+		ret = kvm_hv_send_ipi(vcpu, ingpa, outgpa, true, false);
+		break;
 	default:
 		ret = HV_STATUS_INVALID_HYPERCALL_CODE;
 		break;
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index 0f997683404f..0659465a745c 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -1418,6 +1418,48 @@ TRACE_EVENT(kvm_hv_flush_tlb_ex,
 		  __entry->valid_bank_mask, __entry->format,
 		  __entry->address_space, __entry->flags)
 );
+
+/*
+ * Tracepoints for kvm_hv_send_ipi.
+ */
+TRACE_EVENT(kvm_hv_send_ipi,
+	TP_PROTO(u32 vector, u64 processor_mask),
+	TP_ARGS(vector, processor_mask),
+
+	TP_STRUCT__entry(
+		__field(u32, vector)
+		__field(u64, processor_mask)
+	),
+
+	TP_fast_assign(
+		__entry->vector = vector;
+		__entry->processor_mask = processor_mask;
+	),
+
+	TP_printk("vector %x processor_mask 0x%llx",
+		  __entry->vector, __entry->processor_mask)
+);
+
+TRACE_EVENT(kvm_hv_send_ipi_ex,
+	TP_PROTO(u32 vector, u64 format, u64 valid_bank_mask),
+	TP_ARGS(vector, format, valid_bank_mask),
+
+	TP_STRUCT__entry(
+		__field(u32, vector)
+		__field(u64, format)
+		__field(u64, valid_bank_mask)
+	),
+
+	TP_fast_assign(
+		__entry->vector = vector;
+		__entry->format = format;
+		__entry->valid_bank_mask = valid_bank_mask;
+	),
+
+	TP_printk("vector %x format %llx valid_bank_mask 0x%llx",
+		  __entry->vector, __entry->format,
+		  __entry->valid_bank_mask)
+);
 #endif /* _TRACE_KVM_H */
 
 #undef TRACE_INCLUDE_PATH
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0046aa70205a..1884b66de9c2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2874,6 +2874,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_HYPERV_VP_INDEX:
 	case KVM_CAP_HYPERV_EVENTFD:
 	case KVM_CAP_HYPERV_TLBFLUSH:
+	case KVM_CAP_HYPERV_SEND_IPI:
 	case KVM_CAP_PCI_SEGMENT:
 	case KVM_CAP_DEBUGREGS:
 	case KVM_CAP_X86_ROBUST_SINGLESTEP:
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index b6270a3b38e9..adce915f80a5 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -949,6 +949,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_GET_MSR_FEATURES 153
 #define KVM_CAP_HYPERV_EVENTFD 154
 #define KVM_CAP_HYPERV_TLBFLUSH 155
+#define KVM_CAP_HYPERV_SEND_IPI 156
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.14.4

Re: [PATCH v4 0/5] KVM: x86: hyperv: PV IPI support for Windows guests

[Vitaly Kuznetsov]

Vitaly Kuznetsov <vkuznets@redhat.com> writes:

> Changes since v3 [Roman Kagan]:
> - Don't use vcpu_id in kvm_make_vcpus_request_mask to avoid dealing with
>   sparse CPU masks.
> - Create get_vcpu_idx_by_vpidx() and use it in get_vcpu_by_vpidx() and
>   kvm_hv_flush_tlb().
>
> Using hypercall for sending IPIs is faster because this allows to specify
> any number of vCPUs (even > 64 with sparse CPU set), the whole procedure
> will take only one VMEXIT.
>
> Same as PV TLB flush, this allows Windows guests having > 64 vCPUs to boot
> on KVM when Hyper-V extensions are enabled.

Ping)

-- 
  Vitaly