/*
* 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>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*/
#include <linux/kvm_host.h>
#include <asm/kvm_host.h>
#include <asm/kvm_page_track.h>
#include "mmu.h"
void kvm_page_track_free_memslot(struct kvm_memory_slot *free,
struct kvm_memory_slot *dont)
{
int i;
for (i = 0; i < KVM_PAGE_TRACK_MAX; i++)
if (!dont || free->arch.gfn_track[i] !=
dont->arch.gfn_track[i]) {
kvfree(free->arch.gfn_track[i]);
free->arch.gfn_track[i] = NULL;
}
}
int kvm_page_track_create_memslot(struct kvm_memory_slot *slot,
unsigned long npages)
{
int i;
for (i = 0; i < KVM_PAGE_TRACK_MAX; i++) {
slot->arch.gfn_track[i] = kvm_kvzalloc(npages *
sizeof(*slot->arch.gfn_track[i]));
if (!slot->arch.gfn_track[i])
goto track_free;
}
return 0;
track_free:
kvm_page_track_free_memslot(slot, NULL);
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;
}
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, PT_PAGE_TABLE_LEVEL);
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;
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))
kvm_flush_remote_tlbs(kvm);
}
/*
* 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;
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);
}
/*
* check if the corresponding access on the specified guest page is tracked.
*/
bool kvm_page_track_is_active(struct kvm_vcpu *vcpu, gfn_t gfn,
enum kvm_page_track_mode mode)
{
struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
int index = gfn_to_index(gfn, slot->base_gfn, PT_PAGE_TABLE_LEVEL);
if (WARN_ON(!page_track_mode_is_valid(mode)))
return false;
return !!ACCESS_ONCE(slot->arch.gfn_track[mode][index]);
}
