On Fri, May 05, 2023, zhuangel570 wrote: > FYI, this is our test scenario, simulating the FaaS business, every VM assign > 0.1 core, starting lots VMs run in backgroud (such as 800 VM on a machine > with 80 cores), then burst create 10 VMs, then got 100ms+ latency in creating > "kvm-nx-lpage-recovery". > > On Tue, May 2, 2023 at 10:20 AM Robert Hoo <robert.hoo.linux@xxxxxxxxx> wrote: > > > > On 3/23/2023 3:18 PM, lirongqing@xxxxxxxxx wrote: > > > From: Li RongQing <lirongqing@xxxxxxxxx> > > > > > > if CPU has not X86_BUG_ITLB_MULTIHIT bug, kvm-nx-lpage-re kthread > > > is not needed to create > > > > (directed by Sean from > > https://lore.kernel.org/kvm/ZE%2FR1%2FhvbuWmD8mw@xxxxxxxxxx/ here.) > > > > No, I think it should tie to "nx_huge_pages" value rather than > > directly/partially tie to boot_cpu_has_bug(X86_BUG_ITLB_MULTIHIT). 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")) { + 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; + 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 --
