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Subject[PATCH 4.9 074/107] x86/kvm: Serialize L1D flush parameter setter
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@linutronix.de>

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>
---
arch/x86/kvm/vmx.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- 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

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 c
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)

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