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// SPDX-License-Identifier: GPL-2.0
#ifndef __KVM_X86_MMU_TDP_ITER_H
#define __KVM_X86_MMU_TDP_ITER_H
#include <linux/kvm_host.h>
#include "mmu.h"
#include "spte.h"
/*
* TDP MMU SPTEs are RCU protected to allow paging structures (non-leaf SPTEs)
* to be zapped while holding mmu_lock for read, and to allow TLB flushes to be
* batched without having to collect the list of zapped SPs. Flows that can
* remove SPs must service pending TLB flushes prior to dropping RCU protection.
*/
static inline u64 kvm_tdp_mmu_read_spte(tdp_ptep_t sptep)
{
return READ_ONCE(*rcu_dereference(sptep));
}
static inline u64 kvm_tdp_mmu_write_spte_atomic(tdp_ptep_t sptep, u64 new_spte)
{
return xchg(rcu_dereference(sptep), new_spte);
}
static inline void __kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 new_spte)
{
WRITE_ONCE(*rcu_dereference(sptep), new_spte);
}
/*
* SPTEs must be modified atomically if they are shadow-present, leaf
* SPTEs, and have volatile bits, i.e. has bits that can be set outside
* of mmu_lock. The Writable bit can be set by KVM's fast page fault
* handler, and Accessed and Dirty bits can be set by the CPU.
*
* Note, non-leaf SPTEs do have Accessed bits and those bits are
* technically volatile, but KVM doesn't consume the Accessed bit of
* non-leaf SPTEs, i.e. KVM doesn't care if it clobbers the bit. This
* logic needs to be reassessed if KVM were to use non-leaf Accessed
* bits, e.g. to skip stepping down into child SPTEs when aging SPTEs.
*/
static inline bool kvm_tdp_mmu_spte_need_atomic_write(u64 old_spte, int level)
{
return is_shadow_present_pte(old_spte) &&
is_last_spte(old_spte, level) &&
spte_has_volatile_bits(old_spte);
}
static inline u64 kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 old_spte,
u64 new_spte, int level)
{
if (kvm_tdp_mmu_spte_need_atomic_write(old_spte, level))
return kvm_tdp_mmu_write_spte_atomic(sptep, new_spte);
__kvm_tdp_mmu_write_spte(sptep, new_spte);
return old_spte;
}
static inline u64 tdp_mmu_clear_spte_bits(tdp_ptep_t sptep, u64 old_spte,
u64 mask, int level)
{
atomic64_t *sptep_atomic;
if (kvm_tdp_mmu_spte_need_atomic_write(old_spte, level)) {
sptep_atomic = (atomic64_t *)rcu_dereference(sptep);
return (u64)atomic64_fetch_and(~mask, sptep_atomic);
}
__kvm_tdp_mmu_write_spte(sptep, old_spte & ~mask);
return old_spte;
}
/*
* A TDP iterator performs a pre-order walk over a TDP paging structure.
*/
struct tdp_iter {
/*
* The iterator will traverse the paging structure towards the mapping
* for this GFN.
*/
gfn_t next_last_level_gfn;
/*
* The next_last_level_gfn at the time when the thread last
* yielded. Only yielding when the next_last_level_gfn !=
* yielded_gfn helps ensure forward progress.
*/
gfn_t yielded_gfn;
/* Pointers to the page tables traversed to reach the current SPTE */
tdp_ptep_t pt_path[PT64_ROOT_MAX_LEVEL];
/* A pointer to the current SPTE */
tdp_ptep_t sptep;
/* The lowest GFN mapped by the current SPTE */
gfn_t gfn;
/* The level of the root page given to the iterator */
int root_level;
/* The lowest level the iterator should traverse to */
int min_level;
/* The iterator's current level within the paging structure */
int level;
/* The address space ID, i.e. SMM vs. regular. */
int as_id;
/* A snapshot of the value at sptep */
u64 old_spte;
/*
* Whether the iterator has a valid state. This will be false if the
* iterator walks off the end of the paging structure.
*/
bool valid;
/*
* True if KVM dropped mmu_lock and yielded in the middle of a walk, in
* which case tdp_iter_next() needs to restart the walk at the root
* level instead of advancing to the next entry.
*/
bool yielded;
};
/*
* Iterates over every SPTE mapping the GFN range [start, end) in a
* preorder traversal.
*/
#define for_each_tdp_pte_min_level(iter, root, min_level, start, end) \
for (tdp_iter_start(&iter, root, min_level, start); \
iter.valid && iter.gfn < end; \
tdp_iter_next(&iter))
#define for_each_tdp_pte(iter, root, start, end) \
for_each_tdp_pte_min_level(iter, root, PG_LEVEL_4K, start, end)
tdp_ptep_t spte_to_child_pt(u64 pte, int level);
void tdp_iter_start(struct tdp_iter *iter, struct kvm_mmu_page *root,
int min_level, gfn_t next_last_level_gfn);
void tdp_iter_next(struct tdp_iter *iter);
void tdp_iter_restart(struct tdp_iter *iter);
#endif /* __KVM_X86_MMU_TDP_ITER_H */
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