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KVM: s390: Add FAULT_FLAG_RETRY_NOWAIT for guest fault
In the case of a fault, we will retry to exit sie64 but with gmap fault indication for this thread set. This makes it possible to handle async page faults. Based on a patch from Martin Schwidefsky. Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
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a91b8ebe86
commit
24eb3a824c
4 changed files with 46 additions and 6 deletions
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@ -767,6 +767,7 @@ static inline void pgste_set_pte(pte_t *ptep, pte_t entry)
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* @table: pointer to the page directory
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* @asce: address space control element for gmap page table
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* @crst_list: list of all crst tables used in the guest address space
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* @pfault_enabled: defines if pfaults are applicable for the guest
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*/
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struct gmap {
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struct list_head list;
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@ -775,6 +776,7 @@ struct gmap {
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unsigned long asce;
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void *private;
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struct list_head crst_list;
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bool pfault_enabled;
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};
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/**
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@ -79,6 +79,7 @@ struct thread_struct {
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unsigned long ksp; /* kernel stack pointer */
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mm_segment_t mm_segment;
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unsigned long gmap_addr; /* address of last gmap fault. */
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unsigned int gmap_pfault; /* signal of a pending guest pfault */
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struct per_regs per_user; /* User specified PER registers */
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struct per_event per_event; /* Cause of the last PER trap */
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unsigned long per_flags; /* Flags to control debug behavior */
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@ -255,6 +255,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
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if (!kvm->arch.gmap)
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goto out_nogmap;
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kvm->arch.gmap->private = kvm;
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kvm->arch.gmap->pfault_enabled = 0;
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}
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kvm->arch.css_support = 0;
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@ -701,6 +702,17 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
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return 0;
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}
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static long kvm_arch_fault_in_sync(struct kvm_vcpu *vcpu)
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{
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long rc;
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hva_t fault = gmap_fault(current->thread.gmap_addr, vcpu->arch.gmap);
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struct mm_struct *mm = current->mm;
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down_read(&mm->mmap_sem);
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rc = get_user_pages(current, mm, fault, 1, 1, 0, NULL, NULL);
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up_read(&mm->mmap_sem);
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return rc;
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}
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static int vcpu_pre_run(struct kvm_vcpu *vcpu)
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{
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int rc, cpuflags;
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@ -730,7 +742,7 @@ static int vcpu_pre_run(struct kvm_vcpu *vcpu)
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static int vcpu_post_run(struct kvm_vcpu *vcpu, int exit_reason)
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{
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int rc;
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int rc = -1;
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VCPU_EVENT(vcpu, 6, "exit sie icptcode %d",
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vcpu->arch.sie_block->icptcode);
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@ -744,7 +756,14 @@ static int vcpu_post_run(struct kvm_vcpu *vcpu, int exit_reason)
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current->thread.gmap_addr;
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vcpu->run->s390_ucontrol.pgm_code = 0x10;
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rc = -EREMOTE;
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} else {
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} else if (current->thread.gmap_pfault) {
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current->thread.gmap_pfault = 0;
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if (kvm_arch_fault_in_sync(vcpu) >= 0)
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rc = 0;
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}
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if (rc == -1) {
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VCPU_EVENT(vcpu, 3, "%s", "fault in sie instruction");
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trace_kvm_s390_sie_fault(vcpu);
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rc = kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
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@ -50,6 +50,7 @@
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#define VM_FAULT_BADMAP 0x020000
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#define VM_FAULT_BADACCESS 0x040000
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#define VM_FAULT_SIGNAL 0x080000
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#define VM_FAULT_PFAULT 0x100000
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static unsigned long store_indication __read_mostly;
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@ -227,6 +228,7 @@ static noinline void do_fault_error(struct pt_regs *regs, int fault)
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return;
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}
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case VM_FAULT_BADCONTEXT:
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case VM_FAULT_PFAULT:
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do_no_context(regs);
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break;
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case VM_FAULT_SIGNAL:
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@ -264,6 +266,9 @@ static noinline void do_fault_error(struct pt_regs *regs, int fault)
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*/
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static inline int do_exception(struct pt_regs *regs, int access)
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{
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#ifdef CONFIG_PGSTE
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struct gmap *gmap;
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#endif
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struct task_struct *tsk;
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struct mm_struct *mm;
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struct vm_area_struct *vma;
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@ -304,9 +309,10 @@ static inline int do_exception(struct pt_regs *regs, int access)
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down_read(&mm->mmap_sem);
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#ifdef CONFIG_PGSTE
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if ((current->flags & PF_VCPU) && S390_lowcore.gmap) {
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address = __gmap_fault(address,
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(struct gmap *) S390_lowcore.gmap);
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gmap = (struct gmap *)
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((current->flags & PF_VCPU) ? S390_lowcore.gmap : 0);
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if (gmap) {
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address = __gmap_fault(address, gmap);
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if (address == -EFAULT) {
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fault = VM_FAULT_BADMAP;
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goto out_up;
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@ -315,6 +321,8 @@ static inline int do_exception(struct pt_regs *regs, int access)
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fault = VM_FAULT_OOM;
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goto out_up;
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}
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if (gmap->pfault_enabled)
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flags |= FAULT_FLAG_RETRY_NOWAIT;
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}
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#endif
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@ -371,9 +379,19 @@ static inline int do_exception(struct pt_regs *regs, int access)
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regs, address);
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}
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if (fault & VM_FAULT_RETRY) {
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#ifdef CONFIG_PGSTE
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if (gmap && (flags & FAULT_FLAG_RETRY_NOWAIT)) {
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/* FAULT_FLAG_RETRY_NOWAIT has been set,
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* mmap_sem has not been released */
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current->thread.gmap_pfault = 1;
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fault = VM_FAULT_PFAULT;
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goto out_up;
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}
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#endif
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/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
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* of starvation. */
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flags &= ~FAULT_FLAG_ALLOW_RETRY;
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flags &= ~(FAULT_FLAG_ALLOW_RETRY |
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FAULT_FLAG_RETRY_NOWAIT);
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flags |= FAULT_FLAG_TRIED;
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down_read(&mm->mmap_sem);
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goto retry;
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