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Commit 24eb3a82 authored by Dominik Dingel's avatar Dominik Dingel Committed by Christian Borntraeger
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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: default avatarDominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
parent a91b8ebe

arch/s390/include/asm/pgtable.h

+2 −0
Original line number Diff line number Diff line
@@ -767,6 +767,7 @@ static inline void pgste_set_pte(pte_t *ptep, pte_t entry) 
 * @table: pointer to the page directory

 * @asce: address space control element for gmap page table

 * @crst_list: list of all crst tables used in the guest address space

 * @pfault_enabled: defines if pfaults are applicable for the guest

 */

struct gmap {

	struct list_head list;
@@ -775,6 +776,7 @@ struct gmap { 
	unsigned long asce;

	void *private;

	struct list_head crst_list;

	bool pfault_enabled;

};



/**

arch/s390/include/asm/processor.h

+1 −0
Original line number Diff line number Diff line
@@ -79,6 +79,7 @@ struct thread_struct { 
        unsigned long ksp;              /* kernel stack pointer             */

	mm_segment_t mm_segment;

	unsigned long gmap_addr;	/* address of last gmap fault. */

	unsigned int gmap_pfault;	/* signal of a pending guest pfault */

	struct per_regs per_user;	/* User specified PER registers */

	struct per_event per_event;	/* Cause of the last PER trap */

	unsigned long per_flags;	/* Flags to control debug behavior */

arch/s390/kvm/kvm-s390.c

+21 −2
Original line number Diff line number Diff line
@@ -255,6 +255,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) 
		if (!kvm->arch.gmap)

			goto out_nogmap;

		kvm->arch.gmap->private = kvm;

		kvm->arch.gmap->pfault_enabled = 0;

	}



	kvm->arch.css_support = 0;
@@ -701,6 +702,17 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu) 
	return 0;

}



static long kvm_arch_fault_in_sync(struct kvm_vcpu *vcpu)

{

	long rc;

	hva_t fault = gmap_fault(current->thread.gmap_addr, vcpu->arch.gmap);

	struct mm_struct *mm = current->mm;

	down_read(&mm->mmap_sem);

	rc = get_user_pages(current, mm, fault, 1, 1, 0, NULL, NULL);

	up_read(&mm->mmap_sem);

	return rc;

}



static int vcpu_pre_run(struct kvm_vcpu *vcpu)

{

	int rc, cpuflags;
@@ -730,7 +742,7 @@ static int vcpu_pre_run(struct kvm_vcpu *vcpu) 


static int vcpu_post_run(struct kvm_vcpu *vcpu, int exit_reason)

{

	int rc;

	int rc = -1;



	VCPU_EVENT(vcpu, 6, "exit sie icptcode %d",

		   vcpu->arch.sie_block->icptcode);
@@ -744,7 +756,14 @@ static int vcpu_post_run(struct kvm_vcpu *vcpu, int exit_reason) 
						current->thread.gmap_addr;

		vcpu->run->s390_ucontrol.pgm_code = 0x10;

		rc = -EREMOTE;

	} else {



	} else if (current->thread.gmap_pfault) {

		current->thread.gmap_pfault = 0;

		if (kvm_arch_fault_in_sync(vcpu) >= 0)

			rc = 0;

	}



	if (rc == -1) {

		VCPU_EVENT(vcpu, 3, "%s", "fault in sie instruction");

		trace_kvm_s390_sie_fault(vcpu);

		rc = kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);

arch/s390/mm/fault.c

+22 −4
Original line number Diff line number Diff line
@@ -50,6 +50,7 @@ 
#define VM_FAULT_BADMAP		0x020000

#define VM_FAULT_BADACCESS	0x040000

#define VM_FAULT_SIGNAL		0x080000

#define VM_FAULT_PFAULT		0x100000



static unsigned long store_indication __read_mostly;
@@ -227,6 +228,7 @@ static noinline void do_fault_error(struct pt_regs *regs, int fault) 
			return;

		}

	case VM_FAULT_BADCONTEXT:

	case VM_FAULT_PFAULT:

		do_no_context(regs);

		break;

	case VM_FAULT_SIGNAL:
@@ -264,6 +266,9 @@ static noinline void do_fault_error(struct pt_regs *regs, int fault) 
 */

static inline int do_exception(struct pt_regs *regs, int access)

{

#ifdef CONFIG_PGSTE

	struct gmap *gmap;

#endif

	struct task_struct *tsk;

	struct mm_struct *mm;

	struct vm_area_struct *vma;
@@ -304,9 +309,10 @@ static inline int do_exception(struct pt_regs *regs, int access) 
	down_read(&mm->mmap_sem);



#ifdef CONFIG_PGSTE

	if ((current->flags & PF_VCPU) && S390_lowcore.gmap) {

		address = __gmap_fault(address,

				     (struct gmap *) S390_lowcore.gmap);

	gmap = (struct gmap *)

		((current->flags & PF_VCPU) ? S390_lowcore.gmap : 0);

	if (gmap) {

		address = __gmap_fault(address, gmap);

		if (address == -EFAULT) {

			fault = VM_FAULT_BADMAP;

			goto out_up;
@@ -315,6 +321,8 @@ static inline int do_exception(struct pt_regs *regs, int access) 
			fault = VM_FAULT_OOM;

			goto out_up;

		}

		if (gmap->pfault_enabled)

			flags |= FAULT_FLAG_RETRY_NOWAIT;

	}

#endif
@@ -371,9 +379,19 @@ retry: 
				      regs, address);

		}

		if (fault & VM_FAULT_RETRY) {

#ifdef CONFIG_PGSTE

			if (gmap && (flags & FAULT_FLAG_RETRY_NOWAIT)) {

				/* FAULT_FLAG_RETRY_NOWAIT has been set,

				 * mmap_sem has not been released */

				current->thread.gmap_pfault = 1;

				fault = VM_FAULT_PFAULT;

				goto out_up;

			}

#endif

			/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk

			 * of starvation. */

			flags &= ~FAULT_FLAG_ALLOW_RETRY;

			flags &= ~(FAULT_FLAG_ALLOW_RETRY |

				   FAULT_FLAG_RETRY_NOWAIT);

			flags |= FAULT_FLAG_TRIED;

			down_read(&mm->mmap_sem);

			goto retry;