linux/arch/x86/kvm/mmu/tdp_iter.c

// SPDX-License-Identifier: GPL-2.0
#define pr_fmt(fmt) …

#include "mmu_internal.h"
#include "tdp_iter.h"
#include "spte.h"

/*
 * Recalculates the pointer to the SPTE for the current GFN and level and
 * reread the SPTE.
 */
static void tdp_iter_refresh_sptep(struct tdp_iter *iter)
{ … }

/*
 * Return the TDP iterator to the root PT and allow it to continue its
 * traversal over the paging structure from there.
 */
void tdp_iter_restart(struct tdp_iter *iter)
{ … }

/*
 * Sets a TDP iterator to walk a pre-order traversal of the paging structure
 * rooted at root_pt, starting with the walk to translate next_last_level_gfn.
 */
void tdp_iter_start(struct tdp_iter *iter, struct kvm_mmu_page *root,
		    int min_level, gfn_t next_last_level_gfn)
{ … }

/*
 * Given an SPTE and its level, returns a pointer containing the host virtual
 * address of the child page table referenced by the SPTE. Returns null if
 * there is no such entry.
 */
tdp_ptep_t spte_to_child_pt(u64 spte, int level)
{ … }

/*
 * Steps down one level in the paging structure towards the goal GFN. Returns
 * true if the iterator was able to step down a level, false otherwise.
 */
static bool try_step_down(struct tdp_iter *iter)
{ … }

/*
 * Steps to the next entry in the current page table, at the current page table
 * level. The next entry could point to a page backing guest memory or another
 * page table, or it could be non-present. Returns true if the iterator was
 * able to step to the next entry in the page table, false if the iterator was
 * already at the end of the current page table.
 */
static bool try_step_side(struct tdp_iter *iter)
{ … }

/*
 * Tries to traverse back up a level in the paging structure so that the walk
 * can continue from the next entry in the parent page table. Returns true on a
 * successful step up, false if already in the root page.
 */
static bool try_step_up(struct tdp_iter *iter)
{ … }

/*
 * Step to the next SPTE in a pre-order traversal of the paging structure.
 * To get to the next SPTE, the iterator either steps down towards the goal
 * GFN, if at a present, non-last-level SPTE, or over to a SPTE mapping a
 * higher GFN.
 *
 * The basic algorithm is as follows:
 * 1. If the current SPTE is a non-last-level SPTE, step down into the page
 *    table it points to.
 * 2. If the iterator cannot step down, it will try to step to the next SPTE
 *    in the current page of the paging structure.
 * 3. If the iterator cannot step to the next entry in the current page, it will
 *    try to step up to the parent paging structure page. In this case, that
 *    SPTE will have already been visited, and so the iterator must also step
 *    to the side again.
 */
void tdp_iter_next(struct tdp_iter *iter)
{ … }