Merge tag 'kvm-s390-next-6.18-1' of https://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux into HEAD

KVM: s390: A bugfix and a performance improvement

* Improve interrupt cpu for wakeup, change the heuristic to decide wich
  vCPU to deliver a floating interrupt to.
* Clear the pte when discarding a swapped page because of CMMA; this
  bug was introduced in 6.16 when refactoring gmap code.

Author: bonzini

arch/s390/include/asm/kvm_host.h

@@ -356,7 +356,7 @@ struct kvm_s390_float_interrupt {
 	int counters[FIRQ_MAX_COUNT];
 	struct kvm_s390_mchk_info mchk;
 	struct kvm_s390_ext_info srv_signal;
-	int next_rr_cpu;
+	int last_sleep_cpu;
 	struct mutex ais_lock;
 	u8 simm;
 	u8 nimm;

arch/s390/include/asm/pgtable.h

@@ -2055,4 +2055,26 @@ static inline unsigned long gmap_pgste_get_pgt_addr(unsigned long *pgt)
 	return res;
 }
 
+static inline pgste_t pgste_get_lock(pte_t *ptep)
+{
+	unsigned long value = 0;
+#ifdef CONFIG_PGSTE
+	unsigned long *ptr = (unsigned long *)(ptep + PTRS_PER_PTE);
+
+	do {
+		value = __atomic64_or_barrier(PGSTE_PCL_BIT, ptr);
+	} while (value & PGSTE_PCL_BIT);
+	value |= PGSTE_PCL_BIT;
+#endif
+	return __pgste(value);
+}
+
+static inline void pgste_set_unlock(pte_t *ptep, pgste_t pgste)
+{
+#ifdef CONFIG_PGSTE
+	barrier();
+	WRITE_ONCE(*(unsigned long *)(ptep + PTRS_PER_PTE), pgste_val(pgste) & ~PGSTE_PCL_BIT);
+#endif
+}
+
 #endif /* _S390_PAGE_H */

arch/s390/kvm/interrupt.c

@@ -1323,6 +1323,7 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu)
 	VCPU_EVENT(vcpu, 4, "enabled wait: %llu ns", sltime);
 no_timer:
 	kvm_vcpu_srcu_read_unlock(vcpu);
+	vcpu->kvm->arch.float_int.last_sleep_cpu = vcpu->vcpu_idx;
 	kvm_vcpu_halt(vcpu);
 	vcpu->valid_wakeup = false;
 	__unset_cpu_idle(vcpu);
@@ -1949,18 +1950,15 @@ static void __floating_irq_kick(struct kvm *kvm, u64 type)
 	if (!online_vcpus)
 		return;
 
-	/* find idle VCPUs first, then round robin */
-	sigcpu = find_first_bit(kvm->arch.idle_mask, online_vcpus);
-	if (sigcpu == online_vcpus) {
-		do {
-			sigcpu = kvm->arch.float_int.next_rr_cpu++;
-			kvm->arch.float_int.next_rr_cpu %= online_vcpus;
-			/* avoid endless loops if all vcpus are stopped */
-			if (nr_tries++ >= online_vcpus)
-				return;
-		} while (is_vcpu_stopped(kvm_get_vcpu(kvm, sigcpu)));
+	for (sigcpu = kvm->arch.float_int.last_sleep_cpu; ; sigcpu++) {
+		sigcpu %= online_vcpus;
+		dst_vcpu = kvm_get_vcpu(kvm, sigcpu);
+		if (!is_vcpu_stopped(dst_vcpu))
+			break;
+		/* avoid endless loops if all vcpus are stopped */
+		if (nr_tries++ >= online_vcpus)
+			return;
 	}
-	dst_vcpu = kvm_get_vcpu(kvm, sigcpu);
 
 	/* make the VCPU drop out of the SIE, or wake it up if sleeping */
 	switch (type) {

arch/s390/mm/gmap_helpers.c

@@ -15,6 +15,7 @@
 #include <linux/pagewalk.h>
 #include <linux/ksm.h>
 #include <asm/gmap_helpers.h>
+#include <asm/pgtable.h>
 
 /**
  * ptep_zap_swap_entry() - discard a swap entry.
@@ -47,6 +48,7 @@ void gmap_helper_zap_one_page(struct mm_struct *mm, unsigned long vmaddr)
 {
 	struct vm_area_struct *vma;
 	spinlock_t *ptl;
+	pgste_t pgste;
 	pte_t *ptep;
 
 	mmap_assert_locked(mm);
@@ -60,8 +62,16 @@ void gmap_helper_zap_one_page(struct mm_struct *mm, unsigned long vmaddr)
 	ptep = get_locked_pte(mm, vmaddr, &ptl);
 	if (unlikely(!ptep))
 		return;
-	if (pte_swap(*ptep))
+	if (pte_swap(*ptep)) {
+		preempt_disable();
+		pgste = pgste_get_lock(ptep);
+
 		ptep_zap_swap_entry(mm, pte_to_swp_entry(*ptep));
+		pte_clear(mm, vmaddr, ptep);
+
+		pgste_set_unlock(ptep, pgste);
+		preempt_enable();
+	}
 	pte_unmap_unlock(ptep, ptl);
 }
 EXPORT_SYMBOL_GPL(gmap_helper_zap_one_page);

arch/s390/mm/pgtable.c

@@ -24,6 +24,7 @@
 #include <asm/tlbflush.h>
 #include <asm/mmu_context.h>
 #include <asm/page-states.h>
+#include <asm/pgtable.h>
 #include <asm/machine.h>
 
 pgprot_t pgprot_writecombine(pgprot_t prot)
@@ -115,28 +116,6 @@ static inline pte_t ptep_flush_lazy(struct mm_struct *mm,
 	return old;
 }
 
-static inline pgste_t pgste_get_lock(pte_t *ptep)
-{
-	unsigned long value = 0;
-#ifdef CONFIG_PGSTE
-	unsigned long *ptr = (unsigned long *)(ptep + PTRS_PER_PTE);
-
-	do {
-		value = __atomic64_or_barrier(PGSTE_PCL_BIT, ptr);
-	} while (value & PGSTE_PCL_BIT);
-	value |= PGSTE_PCL_BIT;
-#endif
-	return __pgste(value);
-}
-
-static inline void pgste_set_unlock(pte_t *ptep, pgste_t pgste)
-{
-#ifdef CONFIG_PGSTE
-	barrier();
-	WRITE_ONCE(*(unsigned long *)(ptep + PTRS_PER_PTE), pgste_val(pgste) & ~PGSTE_PCL_BIT);
-#endif
-}
-
 static inline pgste_t pgste_get(pte_t *ptep)
 {
 	unsigned long pgste = 0;