gmap-vsie.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Guest memory management for KVM/s390 nested VMs.
  4 *
  5 * Copyright IBM Corp. 2008, 2020, 2024
  6 *
  7 *    Author(s): Claudio Imbrenda <imbrenda@linux.ibm.com>
  8 *               Martin Schwidefsky <schwidefsky@de.ibm.com>
  9 *               David Hildenbrand <david@redhat.com>
 10 *               Janosch Frank <frankja@linux.vnet.ibm.com>
 11 */
 12
 13#include <linux/compiler.h>
 14#include <linux/kvm.h>
 15#include <linux/kvm_host.h>
 16#include <linux/pgtable.h>
 17#include <linux/pagemap.h>
 18#include <linux/mman.h>
 19
 20#include <asm/lowcore.h>
 21#include <asm/gmap.h>
 22#include <asm/uv.h>
 23
 24#include "kvm-s390.h"
 25
 26/**
 27 * gmap_find_shadow - find a specific asce in the list of shadow tables
 28 * @parent: pointer to the parent gmap
 29 * @asce: ASCE for which the shadow table is created
 30 * @edat_level: edat level to be used for the shadow translation
 31 *
 32 * Returns the pointer to a gmap if a shadow table with the given asce is
 33 * already available, ERR_PTR(-EAGAIN) if another one is just being created,
 34 * otherwise NULL
 35 *
 36 * Context: Called with parent->shadow_lock held
 37 */
 38static struct gmap *gmap_find_shadow(struct gmap *parent, unsigned long asce, int edat_level)
 39{
 40	struct gmap *sg;
 41
 42	lockdep_assert_held(&parent->shadow_lock);
 43	list_for_each_entry(sg, &parent->children, list) {
 44		if (!gmap_shadow_valid(sg, asce, edat_level))
 45			continue;
 46		if (!sg->initialized)
 47			return ERR_PTR(-EAGAIN);
 48		refcount_inc(&sg->ref_count);
 49		return sg;
 50	}
 51	return NULL;
 52}
 53
 54/**
 55 * gmap_shadow - create/find a shadow guest address space
 56 * @parent: pointer to the parent gmap
 57 * @asce: ASCE for which the shadow table is created
 58 * @edat_level: edat level to be used for the shadow translation
 59 *
 60 * The pages of the top level page table referred by the asce parameter
 61 * will be set to read-only and marked in the PGSTEs of the kvm process.
 62 * The shadow table will be removed automatically on any change to the
 63 * PTE mapping for the source table.
 64 *
 65 * Returns a guest address space structure, ERR_PTR(-ENOMEM) if out of memory,
 66 * ERR_PTR(-EAGAIN) if the caller has to retry and ERR_PTR(-EFAULT) if the
 67 * parent gmap table could not be protected.
 68 */
 69struct gmap *gmap_shadow(struct gmap *parent, unsigned long asce, int edat_level)
 70{
 71	struct gmap *sg, *new;
 72	unsigned long limit;
 73	int rc;
 74
 75	if (KVM_BUG_ON(parent->mm->context.allow_gmap_hpage_1m, (struct kvm *)parent->private) ||
 76	    KVM_BUG_ON(gmap_is_shadow(parent), (struct kvm *)parent->private))
 77		return ERR_PTR(-EFAULT);
 78	spin_lock(&parent->shadow_lock);
 79	sg = gmap_find_shadow(parent, asce, edat_level);
 80	spin_unlock(&parent->shadow_lock);
 81	if (sg)
 82		return sg;
 83	/* Create a new shadow gmap */
 84	limit = -1UL >> (33 - (((asce & _ASCE_TYPE_MASK) >> 2) * 11));
 85	if (asce & _ASCE_REAL_SPACE)
 86		limit = -1UL;
 87	new = gmap_alloc(limit);
 88	if (!new)
 89		return ERR_PTR(-ENOMEM);
 90	new->mm = parent->mm;
 91	new->parent = gmap_get(parent);
 92	new->private = parent->private;
 93	new->orig_asce = asce;
 94	new->edat_level = edat_level;
 95	new->initialized = false;
 96	spin_lock(&parent->shadow_lock);
 97	/* Recheck if another CPU created the same shadow */
 98	sg = gmap_find_shadow(parent, asce, edat_level);
 99	if (sg) {
100		spin_unlock(&parent->shadow_lock);
101		gmap_free(new);
102		return sg;
103	}
104	if (asce & _ASCE_REAL_SPACE) {
105		/* only allow one real-space gmap shadow */
106		list_for_each_entry(sg, &parent->children, list) {
107			if (sg->orig_asce & _ASCE_REAL_SPACE) {
108				spin_lock(&sg->guest_table_lock);
109				gmap_unshadow(sg);
110				spin_unlock(&sg->guest_table_lock);
111				list_del(&sg->list);
112				gmap_put(sg);
113				break;
114			}
115		}
116	}
117	refcount_set(&new->ref_count, 2);
118	list_add(&new->list, &parent->children);
119	if (asce & _ASCE_REAL_SPACE) {
120		/* nothing to protect, return right away */
121		new->initialized = true;
122		spin_unlock(&parent->shadow_lock);
123		return new;
124	}
125	spin_unlock(&parent->shadow_lock);
126	/* protect after insertion, so it will get properly invalidated */
127	mmap_read_lock(parent->mm);
128	rc = __kvm_s390_mprotect_many(parent, asce & _ASCE_ORIGIN,
129				      ((asce & _ASCE_TABLE_LENGTH) + 1),
130				      PROT_READ, GMAP_NOTIFY_SHADOW);
131	mmap_read_unlock(parent->mm);
132	spin_lock(&parent->shadow_lock);
133	new->initialized = true;
134	if (rc) {
135		list_del(&new->list);
136		gmap_free(new);
137		new = ERR_PTR(rc);
138	}
139	spin_unlock(&parent->shadow_lock);
140	return new;
141}