From: "K. Y. Srinivasan" <kys@microsoft.com>
Date: Tue, 3 Jul 2018 16:01:55 -0700
Patch-mainline: v4.18-rc4
Subject: x86/hyper-v: Fix the circular dependency in IPI enlightenment
Git-commit: 1268ed0c474a5c8f165ef386f3310521b5e00e27
References: bsc#1107207

The IPI hypercalls depend on being able to map the Linux notion of CPU ID
to the hypervisor's notion of the CPU ID. The array hv_vp_index[] provides
this mapping. Code for populating this array depends on the IPI functionality.
Break this circular dependency.

[ tglx: Use a proper define instead of '-1' with a u32 variable as pointed
  	out by Vitaly ]

Fixes: 68bb7bfb7985 ("X86/Hyper-V: Enable IPI enlightenments")
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Cc: gregkh@linuxfoundation.org
Cc: devel@linuxdriverproject.org
Cc: olaf@aepfle.de
Cc: apw@canonical.com
Cc: jasowang@redhat.com
Cc: hpa@zytor.com
Cc: sthemmin@microsoft.com
Cc: Michael.H.Kelley@microsoft.com
Cc: vkuznets@redhat.com
Link: https://lkml.kernel.org/r/20180703230155.15160-1-kys@linuxonhyperv.com
Acked-by: Olaf Hering <ohering@suse.de>
---
 arch/x86/hyperv/hv_apic.c       | 5 +++++
 arch/x86/hyperv/hv_init.c       | 5 ++++-
 arch/x86/include/asm/mshyperv.h | 5 ++++-
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
--- a/arch/x86/hyperv/hv_apic.c
+++ b/arch/x86/hyperv/hv_apic.c
@@ -114,6 +114,8 @@ static bool __send_ipi_mask_ex(const struct cpumask *mask, int vector)
 		ipi_arg->vp_set.format = HV_GENERIC_SET_SPARSE_4K;
 		nr_bank = cpumask_to_vpset(&(ipi_arg->vp_set), mask);
 	}
+	if (nr_bank < 0)
+		goto ipi_mask_ex_done;
 	if (!nr_bank)
 		ipi_arg->vp_set.format = HV_GENERIC_SET_ALL;
 
@@ -158,6 +160,9 @@ static bool __send_ipi_mask(const struct cpumask *mask, int vector)
 
 	for_each_cpu(cur_cpu, mask) {
 		vcpu = hv_cpu_number_to_vp_number(cur_cpu);
+		if (vcpu == VP_INVAL)
+			goto ipi_mask_done;
+
 		/*
 		 * This particular version of the IPI hypercall can
 		 * only target upto 64 CPUs.
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -265,7 +265,7 @@ void __init hyperv_init(void)
 {
 	u64 guest_id, required_msrs;
 	union hv_x64_msr_hypercall_contents hypercall_msr;
-	int cpuhp;
+	int cpuhp, i;
 
 	if (x86_hyper_type != X86_HYPER_MS_HYPERV)
 		return;
@@ -293,6 +293,9 @@ void __init hyperv_init(void)
 	if (!hv_vp_index)
 		return;
 
+	for (i = 0; i < num_possible_cpus(); i++)
+		hv_vp_index[i] = VP_INVAL;
+
 	hv_vp_assist_page = kcalloc(num_possible_cpus(),
 				    sizeof(*hv_vp_assist_page), GFP_KERNEL);
 	if (!hv_vp_assist_page) {
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -9,6 +9,8 @@
 #include <asm/hyperv-tlfs.h>
 #include <asm/nospec-branch.h>
 
+#define VP_INVAL	U32_MAX
+
 struct ms_hyperv_info {
 	u32 features;
 	u32 misc_features;
@@ -20,7 +22,6 @@ struct ms_hyperv_info {
 
 extern struct ms_hyperv_info ms_hyperv;
 
-
 /*
  * Generate the guest ID.
  */
@@ -281,6 +282,8 @@ static inline int cpumask_to_vpset(struct hv_vpset *vpset,
 	 */
 	for_each_cpu(cpu, cpus) {
 		vcpu = hv_cpu_number_to_vp_number(cpu);
+		if (vcpu == VP_INVAL)
+			return -1;
 		vcpu_bank = vcpu / 64;
 		vcpu_offset = vcpu % 64;
 		__set_bit(vcpu_offset, (unsigned long *)