commit fe30a30f5906c1bea13ee224fbe34f994cb42d5d
author Thomas Gleixner <tglx@linutronix.de> Fri Jul 13 16:23:22 2018 +0200
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> Wed Aug 15 17:37:30 2018 +0200
tree 75e1142d174ac470cd118c26d778ec91c4598e32
parent 8b2f15b4f2a824d57e4a77fe6dcf06b8dbca3fde

x86/kvm: Allow runtime control of L1D flush

commit 895ae47f9918833c3a880fbccd41e0692b37e7d9 upstream.

All mitigation modes can be switched at run time with a static key now:

 - Use sysfs_streq() instead of strcmp() to handle the trailing new line
   from sysfs writes correctly.
 - Make the static key management handle multiple invocations properly.
 - Set the module parameter file to RW

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jiri Kosina <jkosina@suse.cz>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20180713142322.954525119@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/kernel/cpu/bugs.c

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 125de85..4f172c6 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -639,7 +639,7 @@
 #define pr_fmt(fmt)	"L1TF: " fmt
 
 #if IS_ENABLED(CONFIG_KVM_INTEL)
-enum vmx_l1d_flush_state l1tf_vmx_mitigation __ro_after_init = VMENTER_L1D_FLUSH_AUTO;
+enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_AUTO;
 EXPORT_SYMBOL_GPL(l1tf_vmx_mitigation);
 #endif
 

arch/x86/kvm/vmx.c

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index ac10cb9..20c9f40 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -234,12 +234,15 @@
 
 	l1tf_vmx_mitigation = l1tf;
 
-	if (l1tf == VMENTER_L1D_FLUSH_NEVER)
-		return 0;
+	if (l1tf != VMENTER_L1D_FLUSH_NEVER)
+		static_branch_enable(&vmx_l1d_should_flush);
+	else
+		static_branch_disable(&vmx_l1d_should_flush);
 
-	static_branch_enable(&vmx_l1d_should_flush);
 	if (l1tf == VMENTER_L1D_FLUSH_ALWAYS)
 		static_branch_enable(&vmx_l1d_flush_always);
+	else
+		static_branch_disable(&vmx_l1d_flush_always);
 	return 0;
 }
 
@@ -249,7 +252,7 @@
 
 	if (s) {
 		for (i = 0; i < ARRAY_SIZE(vmentry_l1d_param); i++) {
-			if (!strcmp(s, vmentry_l1d_param[i].option))
+			if (sysfs_streq(s, vmentry_l1d_param[i].option))
 				return vmentry_l1d_param[i].cmd;
 		}
 	}
@@ -293,7 +296,7 @@
 	.set = vmentry_l1d_flush_set,
 	.get = vmentry_l1d_flush_get,
 };
-module_param_cb(vmentry_l1d_flush, &vmentry_l1d_flush_ops, NULL, S_IRUGO);
+module_param_cb(vmentry_l1d_flush, &vmentry_l1d_flush_ops, NULL, 0644);
 
 struct kvm_vmx {
 	struct kvm kvm;