x86/kvm: Serialize L1D flush parameter setter
commit dd4bfa739a72508b75760b393d129ed7b431daab upstream
Writes to the parameter files are not serialized at the sysfs core
level, so local serialization is required.
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/20180713142322.873642605@linutronix.de
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 332d92d..ad51ebb 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -194,6 +194,7 @@ extern const ulong vmx_return;
static DEFINE_STATIC_KEY_FALSE(vmx_l1d_should_flush);
static DEFINE_STATIC_KEY_FALSE(vmx_l1d_flush_always);
+static DEFINE_MUTEX(vmx_l1d_flush_mutex);
/* Storage for pre module init parameter parsing */
static enum vmx_l1d_flush_state __read_mostly vmentry_l1d_flush_param = VMENTER_L1D_FLUSH_AUTO;
@@ -258,7 +259,7 @@ static int vmentry_l1d_flush_parse(const char *s)
static int vmentry_l1d_flush_set(const char *s, const struct kernel_param *kp)
{
- int l1tf;
+ int l1tf, ret;
if (!boot_cpu_has(X86_BUG_L1TF))
return 0;
@@ -278,7 +279,10 @@ static int vmentry_l1d_flush_set(const char *s, const struct kernel_param *kp)
return 0;
}
- return vmx_setup_l1d_flush(l1tf);
+ mutex_lock(&vmx_l1d_flush_mutex);
+ ret = vmx_setup_l1d_flush(l1tf);
+ mutex_unlock(&vmx_l1d_flush_mutex);
+ return ret;
}
static int vmentry_l1d_flush_get(char *s, const struct kernel_param *kp)