kvm/x86: Inherit userspace's core scheduling cookie

When creating kvm-pit and kvm_nx_huge_page_recovery_worker threads assign
them the calling process' core scheduling cookie.

Orabug: 34152329

Signed-off-by: Boris Ostrovsky <[email protected]>
Reviewed-by: Libo Chen <[email protected]>
Reviewed-by: Chris Hyser <[email protected]>

Author: Boris Ostrovsky

arch/x86/include/asm/kvm_host.h

@@ -1984,6 +1984,7 @@ void kvm_fire_mask_notifiers(struct kvm *kvm, unsigned irqchip, unsigned pin,
 extern bool tdp_enabled;
 
 u64 vcpu_tsc_khz(struct kvm_vcpu *vcpu);
+extern bool inherit_cs_cookie;
 
 /*
  * EMULTYPE_NO_DECODE - Set when re-emulating an instruction (after completing

arch/x86/kvm/i8254.c

@@ -685,6 +685,9 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags)
 	if (IS_ERR(pit->worker))
 		goto fail_kthread;
 
+	if (inherit_cs_cookie)
+		sched_cs_copy(current, pit->worker->task);
+
 	kthread_init_work(&pit->expired, pit_do_work);
 
 	pit->kvm = kvm;

arch/x86/kvm/mmu/mmu.c

@@ -7578,8 +7578,13 @@ int kvm_mmu_post_init_vm(struct kvm *kvm)
 	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);
-	if (!err)
+	if (!err) {
+		if (inherit_cs_cookie)
+			sched_cs_copy(current,
+				      kvm->arch.nx_huge_page_recovery_thread);
+
 		kthread_unpark(kvm->arch.nx_huge_page_recovery_thread);
+	}
 
 	return err;
 }

arch/x86/kvm/x86.c

@@ -197,6 +197,9 @@ module_param(eager_page_split, bool, 0644);
 static bool __read_mostly mitigate_smt_rsb;
 module_param(mitigate_smt_rsb, bool, 0444);
 
+bool __read_mostly inherit_cs_cookie;
+module_param(inherit_cs_cookie, bool, S_IRUGO);
+
 /*
  * Restoring the host value for MSRs that are only consumed when running in
  * usermode, e.g. SYSCALL MSRs and TSC_AUX, can be deferred until the CPU