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x86/kvm: Allow runtime control of L1D flush

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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
This commit is contained in:
Thomas Gleixner 2018-07-13 16:23:22 +02:00
parent dd4bfa739a
commit 895ae47f99
2 changed files with 9 additions and 6 deletions
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2
arch/x86/kernel/cpu/bugs.c
View File

@ -660,7 +660,7 @@ void x86_spec_ctrl_setup_ap(void)
#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

13
arch/x86/kvm/vmx.c
View File

@ -234,12 +234,15 @@ static int vmx_setup_l1d_flush(enum vmx_l1d_flush_state l1tf)
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);
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 @@ static int vmentry_l1d_flush_parse(const char *s)
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 @@ static const struct kernel_param_ops vmentry_l1d_flush_ops = {
.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;