[PATCH 1/1] x86/hyperv: Update comment in hyperv_cleanup()

[mhkelley58@gmail.com]

From: Michael Kelley <mhklinux@outlook.com>

The comment in hyperv_cleanup() became out-of-date as a result of
commit c8ed0812646e ("x86/hyperv: Use direct call to hypercall-page").

Update the comment. No code or functional change.

Signed-off-by: Michael Kelley <mhklinux@outlook.com>
---
 arch/x86/hyperv/hv_init.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 14de43f4bc6c..a777e43a5de1 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -633,9 +633,13 @@ void hyperv_cleanup(void)
 	hv_ivm_msr_write(HV_X64_MSR_GUEST_OS_ID, 0);
 
 	/*
-	 * Reset hypercall page reference before reset the page,
-	 * let hypercall operations fail safely rather than
-	 * panic the kernel for using invalid hypercall page
+	 * Reset hv_hypercall_pg before resetting it in the hypervisor.
+	 * hv_set_hypercall_pg(NULL) is not used because at this point in the
+	 * panic path other CPUs have been stopped, causing static_call_update()
+	 * to hang. So resetting hv_hypercall_pg to cause hypercalls to fail
+	 * cleanly is only operative on 32-bit builds. But this is OK as it is
+	 * just a preventative measure to ease detecting a hypercall being made
+	 * after this point, which shouldn't be happening anyway.
 	 */
 	hv_hypercall_pg = NULL;
 
-- 
2.25.1