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KVM: x86/mmu: Factor out tdp_iter_return_to_root

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In tdp_mmu_iter_cond_resched there is a call to tdp_iter_start which
causes the iterator to continue its walk over the paging structure from
the root. This is needed after a yield as paging structure could have
been freed in the interim.

The tdp_iter_start call is not very clear and something of a hack. It
requires exposing tdp_iter fields not used elsewhere in tdp_mmu.c and
the effect is not obvious from the function name. Factor a more aptly
named function out of tdp_iter_start and call it from
tdp_mmu_iter_cond_resched and tdp_iter_start.

No functional change intended.

Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210315233803.2706477-4-bgardon@google.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Ben Gardon 2021-03-15 16:38:02 -07:00 committed by Paolo Bonzini
parent 14f6fec2e8
commit b601c3bc9d
3 changed files with 19 additions and 10 deletions
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24
arch/x86/kvm/mmu/tdp_iter.c
View File

@ -20,6 +20,21 @@ static gfn_t round_gfn_for_level(gfn_t gfn, int level)
return gfn & -KVM_PAGES_PER_HPAGE(level);
}
/*
* 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)
{
iter->yielded_gfn = iter->next_last_level_gfn;
iter->level = iter->root_level;
iter->gfn = round_gfn_for_level(iter->next_last_level_gfn, iter->level);
tdp_iter_refresh_sptep(iter);
iter->valid = true;
}
/*
* 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.
@ -31,16 +46,11 @@ void tdp_iter_start(struct tdp_iter *iter, u64 *root_pt, int root_level,
WARN_ON(root_level > PT64_ROOT_MAX_LEVEL);
iter->next_last_level_gfn = next_last_level_gfn;
iter->yielded_gfn = iter->next_last_level_gfn;
iter->root_level = root_level;
iter->min_level = min_level;
iter->level = root_level;
iter->pt_path[iter->level - 1] = (tdp_ptep_t)root_pt;
iter->pt_path[iter->root_level - 1] = (tdp_ptep_t)root_pt;
iter->gfn = round_gfn_for_level(iter->next_last_level_gfn, iter->level);
tdp_iter_refresh_sptep(iter);
iter->valid = true;
tdp_iter_restart(iter);
}
/*

1
arch/x86/kvm/mmu/tdp_iter.h
View File

@ -63,5 +63,6 @@ void tdp_iter_start(struct tdp_iter *iter, u64 *root_pt, int root_level,
int min_level, gfn_t next_last_level_gfn);
void tdp_iter_next(struct tdp_iter *iter);
tdp_ptep_t tdp_iter_root_pt(struct tdp_iter *iter);
void tdp_iter_restart(struct tdp_iter *iter);
#endif /* __KVM_X86_MMU_TDP_ITER_H */

4
arch/x86/kvm/mmu/tdp_mmu.c
View File

@ -664,9 +664,7 @@ static inline bool tdp_mmu_iter_cond_resched(struct kvm *kvm,
WARN_ON(iter->gfn > iter->next_last_level_gfn);
tdp_iter_start(iter, iter->pt_path[iter->root_level - 1],
iter->root_level, iter->min_level,
iter->next_last_level_gfn);
tdp_iter_restart(iter);
return true;
}