linux-stable/arch/x86/kvm/mmu/page_track.c
Ben Gardon 8283e36abf KVM: x86/mmu: Propagate memslot const qualifier
In preparation for implementing in-place hugepage promotion, various
functions will need to be called from zap_collapsible_spte_range, which
has the const qualifier on its memslot argument. Propagate the const
qualifier to the various functions which will be needed. This just serves
to simplify the following patch.

No functional change intended.

Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20211115234603.2908381-11-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-12-08 04:24:43 -05:00

301 lines
7.5 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Support KVM gust page tracking
*
* This feature allows us to track page access in guest. Currently, only
* write access is tracked.
*
* Copyright(C) 2015 Intel Corporation.
*
* Author:
* Xiao Guangrong <guangrong.xiao@linux.intel.com>
*/
#include <linux/kvm_host.h>
#include <linux/rculist.h>
#include <asm/kvm_page_track.h>
#include "mmu.h"
#include "mmu_internal.h"
bool kvm_page_track_write_tracking_enabled(struct kvm *kvm)
{
return IS_ENABLED(CONFIG_KVM_EXTERNAL_WRITE_TRACKING) ||
!tdp_enabled || kvm_shadow_root_allocated(kvm);
}
void kvm_page_track_free_memslot(struct kvm_memory_slot *slot)
{
int i;
for (i = 0; i < KVM_PAGE_TRACK_MAX; i++) {
kvfree(slot->arch.gfn_track[i]);
slot->arch.gfn_track[i] = NULL;
}
}
int kvm_page_track_create_memslot(struct kvm *kvm,
struct kvm_memory_slot *slot,
unsigned long npages)
{
int i;
for (i = 0; i < KVM_PAGE_TRACK_MAX; i++) {
if (i == KVM_PAGE_TRACK_WRITE &&
!kvm_page_track_write_tracking_enabled(kvm))
continue;
slot->arch.gfn_track[i] =
kvcalloc(npages, sizeof(*slot->arch.gfn_track[i]),
GFP_KERNEL_ACCOUNT);
if (!slot->arch.gfn_track[i])
goto track_free;
}
return 0;
track_free:
kvm_page_track_free_memslot(slot);
return -ENOMEM;
}
static inline bool page_track_mode_is_valid(enum kvm_page_track_mode mode)
{
if (mode < 0 || mode >= KVM_PAGE_TRACK_MAX)
return false;
return true;
}
int kvm_page_track_write_tracking_alloc(struct kvm_memory_slot *slot)
{
unsigned short *gfn_track;
if (slot->arch.gfn_track[KVM_PAGE_TRACK_WRITE])
return 0;
gfn_track = kvcalloc(slot->npages, sizeof(*gfn_track), GFP_KERNEL_ACCOUNT);
if (gfn_track == NULL)
return -ENOMEM;
slot->arch.gfn_track[KVM_PAGE_TRACK_WRITE] = gfn_track;
return 0;
}
static void update_gfn_track(struct kvm_memory_slot *slot, gfn_t gfn,
enum kvm_page_track_mode mode, short count)
{
int index, val;
index = gfn_to_index(gfn, slot->base_gfn, PG_LEVEL_4K);
val = slot->arch.gfn_track[mode][index];
if (WARN_ON(val + count < 0 || val + count > USHRT_MAX))
return;
slot->arch.gfn_track[mode][index] += count;
}
/*
* add guest page to the tracking pool so that corresponding access on that
* page will be intercepted.
*
* It should be called under the protection both of mmu-lock and kvm->srcu
* or kvm->slots_lock.
*
* @kvm: the guest instance we are interested in.
* @slot: the @gfn belongs to.
* @gfn: the guest page.
* @mode: tracking mode, currently only write track is supported.
*/
void kvm_slot_page_track_add_page(struct kvm *kvm,
struct kvm_memory_slot *slot, gfn_t gfn,
enum kvm_page_track_mode mode)
{
if (WARN_ON(!page_track_mode_is_valid(mode)))
return;
if (WARN_ON(mode == KVM_PAGE_TRACK_WRITE &&
!kvm_page_track_write_tracking_enabled(kvm)))
return;
update_gfn_track(slot, gfn, mode, 1);
/*
* new track stops large page mapping for the
* tracked page.
*/
kvm_mmu_gfn_disallow_lpage(slot, gfn);
if (mode == KVM_PAGE_TRACK_WRITE)
if (kvm_mmu_slot_gfn_write_protect(kvm, slot, gfn, PG_LEVEL_4K))
kvm_flush_remote_tlbs(kvm);
}
EXPORT_SYMBOL_GPL(kvm_slot_page_track_add_page);
/*
* remove the guest page from the tracking pool which stops the interception
* of corresponding access on that page. It is the opposed operation of
* kvm_slot_page_track_add_page().
*
* It should be called under the protection both of mmu-lock and kvm->srcu
* or kvm->slots_lock.
*
* @kvm: the guest instance we are interested in.
* @slot: the @gfn belongs to.
* @gfn: the guest page.
* @mode: tracking mode, currently only write track is supported.
*/
void kvm_slot_page_track_remove_page(struct kvm *kvm,
struct kvm_memory_slot *slot, gfn_t gfn,
enum kvm_page_track_mode mode)
{
if (WARN_ON(!page_track_mode_is_valid(mode)))
return;
if (WARN_ON(mode == KVM_PAGE_TRACK_WRITE &&
!kvm_page_track_write_tracking_enabled(kvm)))
return;
update_gfn_track(slot, gfn, mode, -1);
/*
* allow large page mapping for the tracked page
* after the tracker is gone.
*/
kvm_mmu_gfn_allow_lpage(slot, gfn);
}
EXPORT_SYMBOL_GPL(kvm_slot_page_track_remove_page);
/*
* check if the corresponding access on the specified guest page is tracked.
*/
bool kvm_slot_page_track_is_active(struct kvm *kvm,
const struct kvm_memory_slot *slot,
gfn_t gfn, enum kvm_page_track_mode mode)
{
int index;
if (WARN_ON(!page_track_mode_is_valid(mode)))
return false;
if (!slot)
return false;
if (mode == KVM_PAGE_TRACK_WRITE &&
!kvm_page_track_write_tracking_enabled(kvm))
return false;
index = gfn_to_index(gfn, slot->base_gfn, PG_LEVEL_4K);
return !!READ_ONCE(slot->arch.gfn_track[mode][index]);
}
void kvm_page_track_cleanup(struct kvm *kvm)
{
struct kvm_page_track_notifier_head *head;
head = &kvm->arch.track_notifier_head;
cleanup_srcu_struct(&head->track_srcu);
}
int kvm_page_track_init(struct kvm *kvm)
{
struct kvm_page_track_notifier_head *head;
head = &kvm->arch.track_notifier_head;
INIT_HLIST_HEAD(&head->track_notifier_list);
return init_srcu_struct(&head->track_srcu);
}
/*
* register the notifier so that event interception for the tracked guest
* pages can be received.
*/
void
kvm_page_track_register_notifier(struct kvm *kvm,
struct kvm_page_track_notifier_node *n)
{
struct kvm_page_track_notifier_head *head;
head = &kvm->arch.track_notifier_head;
write_lock(&kvm->mmu_lock);
hlist_add_head_rcu(&n->node, &head->track_notifier_list);
write_unlock(&kvm->mmu_lock);
}
EXPORT_SYMBOL_GPL(kvm_page_track_register_notifier);
/*
* stop receiving the event interception. It is the opposed operation of
* kvm_page_track_register_notifier().
*/
void
kvm_page_track_unregister_notifier(struct kvm *kvm,
struct kvm_page_track_notifier_node *n)
{
struct kvm_page_track_notifier_head *head;
head = &kvm->arch.track_notifier_head;
write_lock(&kvm->mmu_lock);
hlist_del_rcu(&n->node);
write_unlock(&kvm->mmu_lock);
synchronize_srcu(&head->track_srcu);
}
EXPORT_SYMBOL_GPL(kvm_page_track_unregister_notifier);
/*
* Notify the node that write access is intercepted and write emulation is
* finished at this time.
*
* The node should figure out if the written page is the one that node is
* interested in by itself.
*/
void kvm_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
int bytes)
{
struct kvm_page_track_notifier_head *head;
struct kvm_page_track_notifier_node *n;
int idx;
head = &vcpu->kvm->arch.track_notifier_head;
if (hlist_empty(&head->track_notifier_list))
return;
idx = srcu_read_lock(&head->track_srcu);
hlist_for_each_entry_srcu(n, &head->track_notifier_list, node,
srcu_read_lock_held(&head->track_srcu))
if (n->track_write)
n->track_write(vcpu, gpa, new, bytes, n);
srcu_read_unlock(&head->track_srcu, idx);
}
/*
* Notify the node that memory slot is being removed or moved so that it can
* drop write-protection for the pages in the memory slot.
*
* The node should figure out it has any write-protected pages in this slot
* by itself.
*/
void kvm_page_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot *slot)
{
struct kvm_page_track_notifier_head *head;
struct kvm_page_track_notifier_node *n;
int idx;
head = &kvm->arch.track_notifier_head;
if (hlist_empty(&head->track_notifier_list))
return;
idx = srcu_read_lock(&head->track_srcu);
hlist_for_each_entry_srcu(n, &head->track_notifier_list, node,
srcu_read_lock_held(&head->track_srcu))
if (n->track_flush_slot)
n->track_flush_slot(kvm, slot, n);
srcu_read_unlock(&head->track_srcu, idx);
}