Merge tag 'hyperv-fixes-signed-20211117' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux

Pull hyperv fixes from Wei Liu:

 - Fix ring size calculation for balloon driver (Boqun Feng)

 - Fix issues in Hyper-V setup code (Sean Christopherson)

* tag 'hyperv-fixes-signed-20211117' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux:
  x86/hyperv: Move required MSRs check to initial platform probing
  x86/hyperv: Fix NULL deref in set_hv_tscchange_cb() if Hyper-V setup fails
  Drivers: hv: balloon: Use VMBUS_RING_SIZE() wrapper for dm_ring_size

1 files changed, 4 insertions, 8 deletions

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 24f4a06ac46a..96eb7db31c8e 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -177,6 +177,9 @@ void set_hv_tscchange_cb(void (*cb)(void))
 		return;
 	}
 
+	if (!hv_vp_index)
+		return;
+
 	hv_reenlightenment_cb = cb;
 
 	/* Make sure callback is registered before we write to MSRs */
@@ -383,20 +386,13 @@ static void __init hv_get_partition_id(void)
  */
 void __init hyperv_init(void)
 {
-	u64 guest_id, required_msrs;
+	u64 guest_id;
 	union hv_x64_msr_hypercall_contents hypercall_msr;
 	int cpuhp;
 
 	if (x86_hyper_type != X86_HYPER_MS_HYPERV)
 		return;
 
-	/* Absolutely required MSRs */
-	required_msrs = HV_MSR_HYPERCALL_AVAILABLE |
-		HV_MSR_VP_INDEX_AVAILABLE;
-
-	if ((ms_hyperv.features & required_msrs) != required_msrs)
-		return;
-
 	if (hv_common_init())
 		return;