From a27328ea392714f2bc106f138191fd465157aafb Mon Sep 17 00:00:00 2001
From: brendabrandy <sogun3@gmail.com>
Date: Tue, 11 Mar 2025 16:19:58 -0700
Subject: [PATCH] bhyve: Suppress unimplemented MSR related warnings

When using bhyve on x86, rdmsr and wrmsr can emit many warnings when
dealing with unimplemented MSRs. An option x86.verbosemsr is created to
control these warnings. By default, the MSR related warnings are
suppressed to avoid spamming the console.

Sponsored by: Netflix
Reviewed by: imp, jhb
Pull Request: https://github.com/freebsd/freebsd-src/pull/1611
---
 usr.sbin/bhyve/amd64/bhyverun_machdep.c |  1 +
 usr.sbin/bhyve/amd64/vmexit.c           | 14 ++++++++++----
 usr.sbin/bhyve/bhyve_config.5           |  5 +++++
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/usr.sbin/bhyve/amd64/bhyverun_machdep.c b/usr.sbin/bhyve/amd64/bhyverun_machdep.c
index d51ad3a5fc0..85af124b553 100644
--- a/usr.sbin/bhyve/amd64/bhyverun_machdep.c
+++ b/usr.sbin/bhyve/amd64/bhyverun_machdep.c
@@ -63,6 +63,7 @@ bhyve_init_config(void)
 	set_config_bool("acpi_tables_in_memory", true);
 	set_config_value("memory.size", "256M");
 	set_config_bool("x86.strictmsr", true);
+	set_config_bool("x86.verbosemsr", false);
 	set_config_value("lpc.fwcfg", "bhyve");
 }
 
diff --git a/usr.sbin/bhyve/amd64/vmexit.c b/usr.sbin/bhyve/amd64/vmexit.c
index e0b9aec2d17..944f5de3464 100644
--- a/usr.sbin/bhyve/amd64/vmexit.c
+++ b/usr.sbin/bhyve/amd64/vmexit.c
@@ -107,8 +107,11 @@ vmexit_rdmsr(struct vmctx *ctx __unused, struct vcpu *vcpu,
 	val = 0;
 	error = emulate_rdmsr(vcpu, vme->u.msr.code, &val);
 	if (error != 0) {
-		EPRINTLN("rdmsr to register %#x on vcpu %d",
-		    vme->u.msr.code, vcpu_id(vcpu));
+		if (get_config_bool("x86.strictmsr") ||
+		    get_config_bool("x86.verbosemsr")) {
+			EPRINTLN("rdmsr to register %#x on vcpu %d",
+			    vme->u.msr.code, vcpu_id(vcpu));
+		}
 		if (get_config_bool("x86.strictmsr")) {
 			vm_inject_gp(vcpu);
 			return (VMEXIT_CONTINUE);
@@ -137,8 +140,11 @@ vmexit_wrmsr(struct vmctx *ctx __unused, struct vcpu *vcpu,
 
 	error = emulate_wrmsr(vcpu, vme->u.msr.code, vme->u.msr.wval);
 	if (error != 0) {
-		EPRINTLN("wrmsr to register %#x(%#lx) on vcpu %d",
-		    vme->u.msr.code, vme->u.msr.wval, vcpu_id(vcpu));
+		if (get_config_bool("x86.strictmsr") ||
+		    get_config_bool("x86.verbosemsr")) {
+			EPRINTLN("wrmsr to register %#x(%#lx) on vcpu %d",
+			    vme->u.msr.code, vme->u.msr.wval, vcpu_id(vcpu));
+		}
 		if (get_config_bool("x86.strictmsr")) {
 			vm_inject_gp(vcpu);
 			return (VMEXIT_CONTINUE);
diff --git a/usr.sbin/bhyve/bhyve_config.5 b/usr.sbin/bhyve/bhyve_config.5
index 3f9d9130787..3dd24ca5fe6 100644
--- a/usr.sbin/bhyve/bhyve_config.5
+++ b/usr.sbin/bhyve/bhyve_config.5
@@ -240,6 +240,11 @@ By default, writes are ignored and reads return all bits set.
 Inject a general protection fault if a guest accesses a Model Specific
 Register (MSR) that is not emulated.
 If this is false, writes are ignored and reads return zero.
+.It Va x86.verbosemsr Ta bool Ta false Ta
+Enable verbose MSR print out. When this option is true,
+messages related to reading from (rdmsr) and writing to (wrmsr)
+MSRs on virtual CPUs will be printed out. This can be useful for
+debugging purposes.
 .It Va x86.vmexit_on_hlt Ta bool Ta false Ta
 Force a VM exit when a guest CPU executes the
 .Dv HLT