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Commit b2d73b2a authored by Martin Schwidefsky's avatar Martin Schwidefsky Committed by Christian Borntraeger
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s390/mm: extended gmap pte notifier 



The current gmap pte notifier forces a pte into to a read-write state.
If the pte is invalidated the gmap notifier is called to inform KVM
that the mapping will go away.

Extend this approach to allow read-write, read-only and no-access
as possible target states and call the pte notifier for any change
to the pte.

This mechanism is used to temporarily set specific access rights for
a pte without doing the heavy work of a true mprotect call.

Reviewed-by: default avatarDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
parent 8ecb1a59

arch/s390/include/asm/gmap.h

+6 −3
Original line number Diff line number Diff line
@@ -59,8 +59,11 @@ void gmap_discard(struct gmap *, unsigned long from, unsigned long to); 
void __gmap_zap(struct gmap *, unsigned long gaddr);

void gmap_unlink(struct mm_struct *, unsigned long *table, unsigned long vmaddr);



void gmap_register_ipte_notifier(struct gmap_notifier *);

void gmap_unregister_ipte_notifier(struct gmap_notifier *);

int gmap_ipte_notify(struct gmap *, unsigned long start, unsigned long len);

void gmap_register_pte_notifier(struct gmap_notifier *);

void gmap_unregister_pte_notifier(struct gmap_notifier *);

void gmap_pte_notify(struct mm_struct *, unsigned long addr, pte_t *);



int gmap_mprotect_notify(struct gmap *, unsigned long start,

			 unsigned long len, int prot);



#endif /* _ASM_S390_GMAP_H */

arch/s390/include/asm/pgtable.h

+2 −0
Original line number Diff line number Diff line
@@ -886,6 +886,8 @@ void ptep_set_pte_at(struct mm_struct *mm, unsigned long addr, 
		     pte_t *ptep, pte_t entry);

void ptep_set_notify(struct mm_struct *mm, unsigned long addr, pte_t *ptep);

void ptep_notify(struct mm_struct *mm, unsigned long addr, pte_t *ptep);

int ptep_force_prot(struct mm_struct *mm, unsigned long gaddr,

		    pte_t *ptep, int prot);

void ptep_zap_unused(struct mm_struct *mm, unsigned long addr,

		     pte_t *ptep , int reset);

void ptep_zap_key(struct mm_struct *mm, unsigned long addr, pte_t *ptep);

arch/s390/kvm/kvm-s390.c

+7 −6
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <linux/init.h>

#include <linux/kvm.h>

#include <linux/kvm_host.h>

#include <linux/mman.h>

#include <linux/module.h>

#include <linux/random.h>

#include <linux/slab.h>
@@ -185,7 +186,7 @@ static struct notifier_block kvm_clock_notifier = { 
int kvm_arch_hardware_setup(void)

{

	gmap_notifier.notifier_call = kvm_gmap_notifier;

	gmap_register_ipte_notifier(&gmap_notifier);

	gmap_register_pte_notifier(&gmap_notifier);

	atomic_notifier_chain_register(&s390_epoch_delta_notifier,

				       &kvm_clock_notifier);

	return 0;
@@ -193,7 +194,7 @@ int kvm_arch_hardware_setup(void) 


void kvm_arch_hardware_unsetup(void)

{

	gmap_unregister_ipte_notifier(&gmap_notifier);

	gmap_unregister_pte_notifier(&gmap_notifier);

	atomic_notifier_chain_unregister(&s390_epoch_delta_notifier,

					 &kvm_clock_notifier);

}
@@ -2272,16 +2273,16 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu) 
		return 0;

	/*

	 * We use MMU_RELOAD just to re-arm the ipte notifier for the

	 * guest prefix page. gmap_ipte_notify will wait on the ptl lock.

	 * guest prefix page. gmap_mprotect_notify will wait on the ptl lock.

	 * This ensures that the ipte instruction for this request has

	 * already finished. We might race against a second unmapper that

	 * wants to set the blocking bit. Lets just retry the request loop.

	 */

	if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu)) {

		int rc;

		rc = gmap_ipte_notify(vcpu->arch.gmap,

		rc = gmap_mprotect_notify(vcpu->arch.gmap,

					  kvm_s390_get_prefix(vcpu),

				      PAGE_SIZE * 2);

					  PAGE_SIZE * 2, PROT_WRITE);

		if (rc)

			return rc;

		goto retry;

arch/s390/mm/gmap.c

+129 −41
Original line number Diff line number Diff line
@@ -553,29 +553,29 @@ static LIST_HEAD(gmap_notifier_list); 
static DEFINE_SPINLOCK(gmap_notifier_lock);



/**

 * gmap_register_ipte_notifier - register a pte invalidation callback

 * gmap_register_pte_notifier - register a pte invalidation callback

 * @nb: pointer to the gmap notifier block

 */

void gmap_register_ipte_notifier(struct gmap_notifier *nb)

void gmap_register_pte_notifier(struct gmap_notifier *nb)

{

	spin_lock(&gmap_notifier_lock);

	list_add_rcu(&nb->list, &gmap_notifier_list);

	spin_unlock(&gmap_notifier_lock);

}

EXPORT_SYMBOL_GPL(gmap_register_ipte_notifier);

EXPORT_SYMBOL_GPL(gmap_register_pte_notifier);



/**

 * gmap_unregister_ipte_notifier - remove a pte invalidation callback

 * gmap_unregister_pte_notifier - remove a pte invalidation callback

 * @nb: pointer to the gmap notifier block

 */

void gmap_unregister_ipte_notifier(struct gmap_notifier *nb)

void gmap_unregister_pte_notifier(struct gmap_notifier *nb)

{

	spin_lock(&gmap_notifier_lock);

	list_del_rcu(&nb->list);

	spin_unlock(&gmap_notifier_lock);

	synchronize_rcu();

}

EXPORT_SYMBOL_GPL(gmap_unregister_ipte_notifier);

EXPORT_SYMBOL_GPL(gmap_unregister_pte_notifier);



/**

 * gmap_call_notifier - call all registered invalidation callbacks
@@ -593,62 +593,150 @@ static void gmap_call_notifier(struct gmap *gmap, unsigned long start, 
}



/**

 * gmap_ipte_notify - mark a range of ptes for invalidation notification

 * gmap_table_walk - walk the gmap page tables

 * @gmap: pointer to guest mapping meta data structure

 * @gaddr: virtual address in the guest address space

 *

 * Returns a table pointer for the given guest address.

 */

static inline unsigned long *gmap_table_walk(struct gmap *gmap,

					     unsigned long gaddr)

{

	unsigned long *table;



	table = gmap->table;

	switch (gmap->asce & _ASCE_TYPE_MASK) {

	case _ASCE_TYPE_REGION1:

		table += (gaddr >> 53) & 0x7ff;

		if (*table & _REGION_ENTRY_INVALID)

			return NULL;

		table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);

		/* Fallthrough */

	case _ASCE_TYPE_REGION2:

		table += (gaddr >> 42) & 0x7ff;

		if (*table & _REGION_ENTRY_INVALID)

			return NULL;

		table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);

		/* Fallthrough */

	case _ASCE_TYPE_REGION3:

		table += (gaddr >> 31) & 0x7ff;

		if (*table & _REGION_ENTRY_INVALID)

			return NULL;

		table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);

		/* Fallthrough */

	case _ASCE_TYPE_SEGMENT:

		table += (gaddr >> 20) & 0x7ff;

	}

	return table;

}



/**

 * gmap_pte_op_walk - walk the gmap page table, get the page table lock

 *		      and return the pte pointer

 * @gmap: pointer to guest mapping meta data structure

 * @gaddr: virtual address in the guest address space

 * @ptl: pointer to the spinlock pointer

 *

 * Returns a pointer to the locked pte for a guest address, or NULL

 */

static pte_t *gmap_pte_op_walk(struct gmap *gmap, unsigned long gaddr,

			       spinlock_t **ptl)

{

	unsigned long *table;



	/* Walk the gmap page table, lock and get pte pointer */

	table = gmap_table_walk(gmap, gaddr);

	if (!table || *table & _SEGMENT_ENTRY_INVALID)

		return NULL;

	return pte_alloc_map_lock(gmap->mm, (pmd_t *) table, gaddr, ptl);

}



/**

 * gmap_pte_op_fixup - force a page in and connect the gmap page table

 * @gmap: pointer to guest mapping meta data structure

 * @gaddr: virtual address in the guest address space

 * @vmaddr: address in the host process address space

 *

 * Returns 0 if the caller can retry __gmap_translate (might fail again),

 * -ENOMEM if out of memory and -EFAULT if anything goes wrong while fixing

 * up or connecting the gmap page table.

 */

static int gmap_pte_op_fixup(struct gmap *gmap, unsigned long gaddr,

			     unsigned long vmaddr)

{

	struct mm_struct *mm = gmap->mm;

	bool unlocked = false;



	if (fixup_user_fault(current, mm, vmaddr, FAULT_FLAG_WRITE, &unlocked))

		return -EFAULT;

	if (unlocked)

		/* lost mmap_sem, caller has to retry __gmap_translate */

		return 0;

	/* Connect the page tables */

	return __gmap_link(gmap, gaddr, vmaddr);

}



/**

 * gmap_pte_op_end - release the page table lock

 * @ptl: pointer to the spinlock pointer

 */

static void gmap_pte_op_end(spinlock_t *ptl)

{

	spin_unlock(ptl);

}



/**

 * gmap_mprotect_notify - change access rights for a range of ptes and

 *                        call the notifier if any pte changes again

 * @gmap: pointer to guest mapping meta data structure

 * @gaddr: virtual address in the guest address space

 * @len: size of area

 * @prot: indicates access rights: PROT_NONE, PROT_READ or PROT_WRITE

 *

 * Returns 0 if for each page in the given range a gmap mapping exists and

 * the invalidation notification could be set. If the gmap mapping is missing

 * for one or more pages -EFAULT is returned. If no memory could be allocated

 * -ENOMEM is returned. This function establishes missing page table entries.

 * Returns 0 if for each page in the given range a gmap mapping exists,

 * the new access rights could be set and the notifier could be armed.

 * If the gmap mapping is missing for one or more pages -EFAULT is

 * returned. If no memory could be allocated -ENOMEM is returned.

 * This function establishes missing page table entries.

 */

int gmap_ipte_notify(struct gmap *gmap, unsigned long gaddr, unsigned long len)

int gmap_mprotect_notify(struct gmap *gmap, unsigned long gaddr,

			 unsigned long len, int prot)

{

	unsigned long addr;

	unsigned long vmaddr;

	spinlock_t *ptl;

	pte_t *ptep;

	bool unlocked;

	int rc = 0;



	if ((gaddr & ~PAGE_MASK) || (len & ~PAGE_MASK))

		return -EINVAL;

	if (!MACHINE_HAS_ESOP && prot == PROT_READ)

		return -EINVAL;

	down_read(&gmap->mm->mmap_sem);

	while (len) {

		unlocked = false;

		/* Convert gmap address and connect the page tables */

		addr = __gmap_translate(gmap, gaddr);

		if (IS_ERR_VALUE(addr)) {

			rc = addr;

			break;

		rc = -EAGAIN;

		ptep = gmap_pte_op_walk(gmap, gaddr, &ptl);

		if (ptep) {

			rc = ptep_force_prot(gmap->mm, gaddr, ptep, prot);

			gmap_pte_op_end(ptl);

		}

		/* Get the page mapped */

		if (fixup_user_fault(current, gmap->mm, addr, FAULT_FLAG_WRITE,

				     &unlocked)) {

			rc = -EFAULT;

		if (rc) {

			vmaddr = __gmap_translate(gmap, gaddr);

			if (IS_ERR_VALUE(vmaddr)) {

				rc = vmaddr;

				break;

			}

		/* While trying to map mmap_sem got unlocked. Let us retry */

		if (unlocked)

			continue;

		rc = __gmap_link(gmap, gaddr, addr);

			rc = gmap_pte_op_fixup(gmap, gaddr, vmaddr);

			if (rc)

				break;

		/* Walk the process page table, lock and get pte pointer */

		ptep = get_locked_pte(gmap->mm, addr, &ptl);

		VM_BUG_ON(!ptep);

		/* Set notification bit in the pgste of the pte */

		if ((pte_val(*ptep) & (_PAGE_INVALID | _PAGE_PROTECT)) == 0) {

			ptep_set_notify(gmap->mm, addr, ptep);

			continue;

		}

		gaddr += PAGE_SIZE;

		len -= PAGE_SIZE;

	}

		pte_unmap_unlock(ptep, ptl);

	}

	up_read(&gmap->mm->mmap_sem);

	return rc;

}

EXPORT_SYMBOL_GPL(gmap_ipte_notify);

EXPORT_SYMBOL_GPL(gmap_mprotect_notify);



/**

 * ptep_notify - call all invalidation callbacks for a specific pte.

arch/s390/mm/pgtable.c

+49 −5
Original line number Diff line number Diff line
@@ -179,7 +179,7 @@ static inline pgste_t pgste_set_pte(pte_t *ptep, pgste_t pgste, pte_t entry) 
	return pgste;

}



static inline pgste_t pgste_ipte_notify(struct mm_struct *mm,

static inline pgste_t pgste_pte_notify(struct mm_struct *mm,

				       unsigned long addr,

				       pte_t *ptep, pgste_t pgste)

{
@@ -199,7 +199,7 @@ static inline pgste_t ptep_xchg_start(struct mm_struct *mm, 


	if (mm_has_pgste(mm)) {

		pgste = pgste_get_lock(ptep);

		pgste = pgste_ipte_notify(mm, addr, ptep, pgste);

		pgste = pgste_pte_notify(mm, addr, ptep, pgste);

	}

	return pgste;

}
@@ -414,6 +414,50 @@ void ptep_set_notify(struct mm_struct *mm, unsigned long addr, pte_t *ptep) 
	pgste_set_unlock(ptep, pgste);

}



/**

 * ptep_force_prot - change access rights of a locked pte

 * @mm: pointer to the process mm_struct

 * @addr: virtual address in the guest address space

 * @ptep: pointer to the page table entry

 * @prot: indicates guest access rights: PROT_NONE, PROT_READ or PROT_WRITE

 *

 * Returns 0 if the access rights were changed and -EAGAIN if the current

 * and requested access rights are incompatible.

 */

int ptep_force_prot(struct mm_struct *mm, unsigned long addr,

		    pte_t *ptep, int prot)

{

	pte_t entry;

	pgste_t pgste;

	int pte_i, pte_p;



	pgste = pgste_get_lock(ptep);

	entry = *ptep;

	/* Check pte entry after all locks have been acquired */

	pte_i = pte_val(entry) & _PAGE_INVALID;

	pte_p = pte_val(entry) & _PAGE_PROTECT;

	if ((pte_i && (prot != PROT_NONE)) ||

	    (pte_p && (prot & PROT_WRITE))) {

		pgste_set_unlock(ptep, pgste);

		return -EAGAIN;

	}

	/* Change access rights and set the pgste notification bit */

	if (prot == PROT_NONE && !pte_i) {

		ptep_flush_direct(mm, addr, ptep);

		pgste = pgste_update_all(entry, pgste, mm);

		pte_val(entry) |= _PAGE_INVALID;

	}

	if (prot == PROT_READ && !pte_p) {

		ptep_flush_direct(mm, addr, ptep);

		pte_val(entry) &= ~_PAGE_INVALID;

		pte_val(entry) |= _PAGE_PROTECT;

	}

	pgste_val(pgste) |= PGSTE_IN_BIT;

	pgste = pgste_set_pte(ptep, pgste, entry);

	pgste_set_unlock(ptep, pgste);

	return 0;

}



static void ptep_zap_swap_entry(struct mm_struct *mm, swp_entry_t entry)

{

	if (!non_swap_entry(entry))
@@ -483,7 +527,7 @@ bool test_and_clear_guest_dirty(struct mm_struct *mm, unsigned long addr) 
	pgste_val(pgste) &= ~PGSTE_UC_BIT;

	pte = *ptep;

	if (dirty && (pte_val(pte) & _PAGE_PRESENT)) {

		pgste = pgste_ipte_notify(mm, addr, ptep, pgste);

		pgste = pgste_pte_notify(mm, addr, ptep, pgste);

		__ptep_ipte(addr, ptep);

		if (MACHINE_HAS_ESOP || !(pte_val(pte) & _PAGE_WRITE))

			pte_val(pte) |= _PAGE_PROTECT;