On 6/2/2023 11:09 PM, Sean Christopherson wrote:
On Fri, Jun 02, 2023, Robert Hoo wrote:
On 6/2/2023 8:58 AM, Sean Christopherson wrote:
@@ -6860,15 +6871,29 @@ static int set_nx_huge_pages(const char *val, const struct kernel_param *kp)
bool old_val = nx_huge_pages;
bool new_val;
+ if (nx_hugepage_mitigation_hard_disabled)
+ return -EPERM;
+
/* In "auto" mode deploy workaround only if CPU has the bug. */
- if (sysfs_streq(val, "off"))
+ if (sysfs_streq(val, "off")) {
new_val = 0;
- else if (sysfs_streq(val, "force"))
+ } else if (sysfs_streq(val, "force")) {
new_val = 1;
- else if (sysfs_streq(val, "auto"))
+ } else if (sysfs_streq(val, "auto")) {
new_val = get_nx_auto_mode();
- else if (kstrtobool(val, &new_val) < 0)
+ } else if (sysfs_streq(val, "never")) {
+ new_val = 0;
+
+ mutex_lock(&kvm_lock);
+ if (!list_empty(&vm_list)) {
+ mutex_unlock(&kvm_lock);
+ return -EBUSY;
Ah, right, thanks for explanation.
Reviewed-by: Robert Hoo <robert.hoo.linux@xxxxxxxxx>
+ }
+ nx_hugepage_mitigation_hard_disabled = true;
+ mutex_unlock(&kvm_lock);
+ } else if (kstrtobool(val, &new_val) < 0) {
return -EINVAL;
+ }
IIUC, (Initially) "auto_off"/"off" --> create some VM --> turn to "never",
the created VMs still have those kthreads, but can never be used, until
destroyed with VM.
Shouldn't be able to happen. The above rejects "never" if vm_list isn't empty,
i.e. if there are any VMs, and sets nx_hugepage_mitigation_hard_disabled under
kvm_lock to ensure it can't race with KVM_CREATE_VM. I forgot to call this out
in the changelog though
