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// SPDX-License-Identifier: GPL-2.0
/*
* Guest memory management for KVM/s390 nested VMs.
*
* Copyright IBM Corp. 2008, 2020, 2024
*
* Author(s): Claudio Imbrenda <imbrenda@linux.ibm.com>
* Martin Schwidefsky <schwidefsky@de.ibm.com>
* David Hildenbrand <david@redhat.com>
* Janosch Frank <frankja@linux.vnet.ibm.com>
*/
#include <linux/compiler.h>
#include <linux/kvm.h>
#include <linux/kvm_host.h>
#include <linux/pgtable.h>
#include <linux/pagemap.h>
#include <linux/mman.h>
#include <asm/lowcore.h>
#include <asm/gmap.h>
#include <asm/uv.h>
#include "kvm-s390.h"
#include "gmap.h"
/**
* gmap_find_shadow - find a specific asce in the list of shadow tables
* @parent: pointer to the parent gmap
* @asce: ASCE for which the shadow table is created
* @edat_level: edat level to be used for the shadow translation
*
* Returns the pointer to a gmap if a shadow table with the given asce is
* already available, ERR_PTR(-EAGAIN) if another one is just being created,
* otherwise NULL
*
* Context: Called with parent->shadow_lock held
*/
static struct gmap *gmap_find_shadow(struct gmap *parent, unsigned long asce, int edat_level)
{
struct gmap *sg;
lockdep_assert_held(&parent->shadow_lock);
list_for_each_entry(sg, &parent->children, list) {
if (!gmap_shadow_valid(sg, asce, edat_level))
continue;
if (!sg->initialized)
return ERR_PTR(-EAGAIN);
refcount_inc(&sg->ref_count);
return sg;
}
return NULL;
}
/**
* gmap_shadow - create/find a shadow guest address space
* @parent: pointer to the parent gmap
* @asce: ASCE for which the shadow table is created
* @edat_level: edat level to be used for the shadow translation
*
* The pages of the top level page table referred by the asce parameter
* will be set to read-only and marked in the PGSTEs of the kvm process.
* The shadow table will be removed automatically on any change to the
* PTE mapping for the source table.
*
* Returns a guest address space structure, ERR_PTR(-ENOMEM) if out of memory,
* ERR_PTR(-EAGAIN) if the caller has to retry and ERR_PTR(-EFAULT) if the
* parent gmap table could not be protected.
*/
struct gmap *gmap_shadow(struct gmap *parent, unsigned long asce, int edat_level)
{
struct gmap *sg, *new;
unsigned long limit;
int rc;
if (KVM_BUG_ON(parent->mm->context.allow_gmap_hpage_1m, (struct kvm *)parent->private) ||
KVM_BUG_ON(gmap_is_shadow(parent), (struct kvm *)parent->private))
return ERR_PTR(-EFAULT);
spin_lock(&parent->shadow_lock);
sg = gmap_find_shadow(parent, asce, edat_level);
spin_unlock(&parent->shadow_lock);
if (sg)
return sg;
/* Create a new shadow gmap */
limit = -1UL >> (33 - (((asce & _ASCE_TYPE_MASK) >> 2) * 11));
if (asce & _ASCE_REAL_SPACE)
limit = -1UL;
new = gmap_alloc(limit);
if (!new)
return ERR_PTR(-ENOMEM);
new->mm = parent->mm;
new->parent = gmap_get(parent);
new->private = parent->private;
new->orig_asce = asce;
new->edat_level = edat_level;
new->initialized = false;
spin_lock(&parent->shadow_lock);
/* Recheck if another CPU created the same shadow */
sg = gmap_find_shadow(parent, asce, edat_level);
if (sg) {
spin_unlock(&parent->shadow_lock);
gmap_free(new);
return sg;
}
if (asce & _ASCE_REAL_SPACE) {
/* only allow one real-space gmap shadow */
list_for_each_entry(sg, &parent->children, list) {
if (sg->orig_asce & _ASCE_REAL_SPACE) {
spin_lock(&sg->guest_table_lock);
gmap_unshadow(sg);
spin_unlock(&sg->guest_table_lock);
list_del(&sg->list);
gmap_put(sg);
break;
}
}
}
refcount_set(&new->ref_count, 2);
list_add(&new->list, &parent->children);
if (asce & _ASCE_REAL_SPACE) {
/* nothing to protect, return right away */
new->initialized = true;
spin_unlock(&parent->shadow_lock);
return new;
}
spin_unlock(&parent->shadow_lock);
/* protect after insertion, so it will get properly invalidated */
mmap_read_lock(parent->mm);
rc = __kvm_s390_mprotect_many(parent, asce & _ASCE_ORIGIN,
((asce & _ASCE_TABLE_LENGTH) + 1),
PROT_READ, GMAP_NOTIFY_SHADOW);
mmap_read_unlock(parent->mm);
spin_lock(&parent->shadow_lock);
new->initialized = true;
if (rc) {
list_del(&new->list);
gmap_free(new);
new = ERR_PTR(rc);
}
spin_unlock(&parent->shadow_lock);
return new;
}
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