On 5/6/2023 1:44 AM, Sean Christopherson wrote:
Lightly tested. This is what I'm thinking for a "never" param. Unless someone
has an alternative idea, I'll post a formal patch after more testing.
---
arch/x86/kvm/mmu/mmu.c | 41 ++++++++++++++++++++++++++++++++++++-----
1 file changed, 36 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index c8961f45e3b1..14713c050196 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -58,6 +58,8 @@
extern bool itlb_multihit_kvm_mitigation;
+static bool nx_hugepage_mitigation_hard_disabled;
+
int __read_mostly nx_huge_pages = -1;
static uint __read_mostly nx_huge_pages_recovery_period_ms;
#ifdef CONFIG_PREEMPT_RT
@@ -67,12 +69,13 @@ static uint __read_mostly nx_huge_pages_recovery_ratio = 0;
static uint __read_mostly nx_huge_pages_recovery_ratio = 60;
#endif
+static int get_nx_huge_pages(char *buffer, const struct kernel_param *kp);
static int set_nx_huge_pages(const char *val, const struct kernel_param *kp);
static int set_nx_huge_pages_recovery_param(const char *val, const struct kernel_param *kp);
static const struct kernel_param_ops nx_huge_pages_ops = {
.set = set_nx_huge_pages,
- .get = param_get_bool,
+ .get = get_nx_huge_pages,
};
static const struct kernel_param_ops nx_huge_pages_recovery_param_ops = {
@@ -6844,6 +6847,14 @@ static void mmu_destroy_caches(void)
kmem_cache_destroy(mmu_page_header_cache);
}
+static int get_nx_huge_pages(char *buffer, const struct kernel_param *kp)
+{
+ if (nx_hugepage_mitigation_hard_disabled)
+ return sprintf(buffer, "never\n");
+
+ return param_get_bool(buffer, kp);
+}
+
static bool get_nx_auto_mode(void)
{
/* Return true when CPU has the bug, and mitigations are ON */
@@ -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)
+ } if (sysfs_streq(val, "never")) {
if --> else if?
And, what's the difference between "off" and "never"?
+ new_val = 0;
+
+ mutex_lock(&kvm_lock);
+ if (!list_empty(&vm_list)) {
+ mutex_unlock(&kvm_lock);
+ return -EBUSY;
+ }
+ nx_hugepage_mitigation_hard_disabled = true;
+ mutex_unlock(&kvm_lock);
+ } else if (kstrtobool(val, &new_val) < 0) {
return -EINVAL;
+ }
__set_nx_huge_pages(new_val);
@@ -7006,6 +7031,9 @@ static int set_nx_huge_pages_recovery_param(const char *val, const struct kernel
uint old_period, new_period;
int err;
+ if (nx_hugepage_mitigation_hard_disabled)
+ return -EPERM;
+
was_recovery_enabled = calc_nx_huge_pages_recovery_period(&old_period);
err = param_set_uint(val, kp);
@@ -7161,6 +7189,9 @@ int kvm_mmu_post_init_vm(struct kvm *kvm)
{
int err;
+ if (nx_hugepage_mitigation_hard_disabled)
+ return 0;
+
I suggest
if (!nx_hugepage_mitigation_hard_disabled) {
create worker thread
}
As this func name is kvm_mmu_post_init_vm(),
nx_hugepage_mitigation_hard_disabled mean don't need to create the worker
thread, but not don't need to do post init, although currently the only
stuff in post init is to create work thread of nx_hugepage, but for the
sake of future stuff.
err = kvm_vm_create_worker_thread(kvm, kvm_nx_huge_page_recovery_worker, 0,
"kvm-nx-lpage-recovery",
&kvm->arch.nx_huge_page_recovery_thread);
base-commit: b3c98052d46948a8d65d2778c7f306ff38366aac
