33a3164161
Prevent the TDP MMU from yielding when zapping a gfn range during NX page recovery. If a flush is pending from a previous invocation of the zapping helper, either in the TDP MMU or the legacy MMU, but the TDP MMU has not accumulated a flush for the current invocation, then yielding will release mmu_lock with stale TLB entries. That being said, this isn't technically a bug fix in the current code, as the TDP MMU will never yield in this case. tdp_mmu_iter_cond_resched() will yield if and only if it has made forward progress, as defined by the current gfn vs. the last yielded (or starting) gfn. Because zapping a single shadow page is guaranteed to (a) find that page and (b) step sideways at the level of the shadow page, the TDP iter will break its loop before getting a chance to yield. But that is all very, very subtle, and will break at the slightest sneeze, e.g. zapping while holding mmu_lock for read would break as the TDP MMU wouldn't be guaranteed to see the present shadow page, and thus could step sideways at a lower level. Cc: Ben Gardon <bgardon@google.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20210325200119.1359384-4-seanjc@google.com> [Add lockdep assertion. - Paolo] Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
96 lines
3.3 KiB
C
96 lines
3.3 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#ifndef __KVM_X86_MMU_TDP_MMU_H
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#define __KVM_X86_MMU_TDP_MMU_H
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#include <linux/kvm_host.h>
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hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu);
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void kvm_tdp_mmu_free_root(struct kvm *kvm, struct kvm_mmu_page *root);
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bool __kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, gfn_t start, gfn_t end,
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bool can_yield);
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static inline bool kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, gfn_t start,
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gfn_t end)
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{
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return __kvm_tdp_mmu_zap_gfn_range(kvm, start, end, true);
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}
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static inline bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
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{
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gfn_t end = sp->gfn + KVM_PAGES_PER_HPAGE(sp->role.level);
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/*
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* Don't allow yielding, as the caller may have a flush pending. Note,
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* if mmu_lock is held for write, zapping will never yield in this case,
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* but explicitly disallow it for safety. The TDP MMU does not yield
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* until it has made forward progress (steps sideways), and when zapping
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* a single shadow page that it's guaranteed to see (thus the mmu_lock
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* requirement), its "step sideways" will always step beyond the bounds
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* of the shadow page's gfn range and stop iterating before yielding.
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*/
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lockdep_assert_held_write(&kvm->mmu_lock);
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return __kvm_tdp_mmu_zap_gfn_range(kvm, sp->gfn, end, false);
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}
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void kvm_tdp_mmu_zap_all(struct kvm *kvm);
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int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
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int map_writable, int max_level, kvm_pfn_t pfn,
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bool prefault);
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int kvm_tdp_mmu_zap_hva_range(struct kvm *kvm, unsigned long start,
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unsigned long end);
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int kvm_tdp_mmu_age_hva_range(struct kvm *kvm, unsigned long start,
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unsigned long end);
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int kvm_tdp_mmu_test_age_hva(struct kvm *kvm, unsigned long hva);
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int kvm_tdp_mmu_set_spte_hva(struct kvm *kvm, unsigned long address,
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pte_t *host_ptep);
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bool kvm_tdp_mmu_wrprot_slot(struct kvm *kvm, struct kvm_memory_slot *slot,
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int min_level);
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bool kvm_tdp_mmu_clear_dirty_slot(struct kvm *kvm,
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struct kvm_memory_slot *slot);
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void kvm_tdp_mmu_clear_dirty_pt_masked(struct kvm *kvm,
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struct kvm_memory_slot *slot,
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gfn_t gfn, unsigned long mask,
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bool wrprot);
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void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm,
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struct kvm_memory_slot *slot);
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bool kvm_tdp_mmu_write_protect_gfn(struct kvm *kvm,
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struct kvm_memory_slot *slot, gfn_t gfn);
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int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes,
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int *root_level);
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#ifdef CONFIG_X86_64
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void kvm_mmu_init_tdp_mmu(struct kvm *kvm);
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void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm);
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static inline bool is_tdp_mmu_enabled(struct kvm *kvm) { return kvm->arch.tdp_mmu_enabled; }
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static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return sp->tdp_mmu_page; }
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#else
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static inline void kvm_mmu_init_tdp_mmu(struct kvm *kvm) {}
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static inline void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm) {}
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static inline bool is_tdp_mmu_enabled(struct kvm *kvm) { return false; }
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static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return false; }
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#endif
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static inline bool is_tdp_mmu_root(struct kvm *kvm, hpa_t hpa)
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{
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struct kvm_mmu_page *sp;
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if (!is_tdp_mmu_enabled(kvm))
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return false;
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if (WARN_ON(!VALID_PAGE(hpa)))
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return false;
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sp = to_shadow_page(hpa);
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if (WARN_ON(!sp))
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return false;
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return is_tdp_mmu_page(sp) && sp->root_count;
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}
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#endif /* __KVM_X86_MMU_TDP_MMU_H */
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