From f47e5bbbc92f5d234bbab317523c64a65b6ac4e2 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 25 Mar 2022 23:03:48 +0000 Subject: [PATCH] KVM: x86/mmu: Zap only TDP MMU leafs in zap range and mmu_notifier unmap Re-introduce zapping only leaf SPTEs in kvm_zap_gfn_range() and kvm_tdp_mmu_unmap_gfn_range(), this time without losing a pending TLB flush when processing multiple roots (including nested TDP shadow roots). Dropping the TLB flush resulted in random crashes when running Hyper-V Server 2019 in a guest with KSM enabled in the host (or any source of mmu_notifier invalidations, KSM is just the easiest to force). This effectively revert commits 873dd122172f8cce329113cfb0dfe3d2344d80c0 and fcb93eb6d09dd302cbef22bd95a5858af75e4156, and thus restores commit cf3e26427c08ad9015956293ab389004ac6a338e, plus this delta on top: bool kvm_tdp_mmu_zap_leafs(struct kvm *kvm, int as_id, gfn_t start, gfn_t end, struct kvm_mmu_page *root; for_each_tdp_mmu_root_yield_safe(kvm, root, as_id) - flush = tdp_mmu_zap_leafs(kvm, root, start, end, can_yield, false); + flush = tdp_mmu_zap_leafs(kvm, root, start, end, can_yield, flush); return flush; } Cc: Ben Gardon Signed-off-by: Sean Christopherson Tested-by: Vitaly Kuznetsov Message-Id: <20220325230348.2587437-1-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu/mmu.c | 4 ++-- arch/x86/kvm/mmu/tdp_mmu.c | 55 ++++++++++++++-------------------------------- arch/x86/kvm/mmu/tdp_mmu.h | 8 +------ 3 files changed, 19 insertions(+), 48 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 857ba93..333aaf6 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -5849,8 +5849,8 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end) if (is_tdp_mmu_enabled(kvm)) { for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) - flush = kvm_tdp_mmu_zap_gfn_range(kvm, i, gfn_start, - gfn_end, flush); + flush = kvm_tdp_mmu_zap_leafs(kvm, i, gfn_start, + gfn_end, true, flush); } if (flush) diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 4be517a..d71d177 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -909,10 +909,8 @@ bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp) } /* - * Tears down the mappings for the range of gfns, [start, end), and frees the - * non-root pages mapping GFNs strictly within that range. Returns true if - * SPTEs have been cleared and a TLB flush is needed before releasing the - * MMU lock. + * Zap leafs SPTEs for the range of gfns, [start, end). Returns true if SPTEs + * have been cleared and a TLB flush is needed before releasing the MMU lock. * * If can_yield is true, will release the MMU lock and reschedule if the * scheduler needs the CPU or there is contention on the MMU lock. If this @@ -920,42 +918,25 @@ bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp) * the caller must ensure it does not supply too large a GFN range, or the * operation can cause a soft lockup. */ -static bool zap_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root, - gfn_t start, gfn_t end, bool can_yield, bool flush) +static bool tdp_mmu_zap_leafs(struct kvm *kvm, struct kvm_mmu_page *root, + gfn_t start, gfn_t end, bool can_yield, bool flush) { - bool zap_all = (start == 0 && end >= tdp_mmu_max_gfn_host()); struct tdp_iter iter; - /* - * No need to try to step down in the iterator when zapping all SPTEs, - * zapping the top-level non-leaf SPTEs will recurse on their children. - */ - int min_level = zap_all ? root->role.level : PG_LEVEL_4K; - end = min(end, tdp_mmu_max_gfn_host()); lockdep_assert_held_write(&kvm->mmu_lock); rcu_read_lock(); - for_each_tdp_pte_min_level(iter, root, min_level, start, end) { + for_each_tdp_pte_min_level(iter, root, PG_LEVEL_4K, start, end) { if (can_yield && tdp_mmu_iter_cond_resched(kvm, &iter, flush, false)) { flush = false; continue; } - if (!is_shadow_present_pte(iter.old_spte)) - continue; - - /* - * If this is a non-last-level SPTE that covers a larger range - * than should be zapped, continue, and zap the mappings at a - * lower level, except when zapping all SPTEs. - */ - if (!zap_all && - (iter.gfn < start || - iter.gfn + KVM_PAGES_PER_HPAGE(iter.level) > end) && + if (!is_shadow_present_pte(iter.old_spte) || !is_last_spte(iter.old_spte, iter.level)) continue; @@ -963,17 +944,13 @@ static bool zap_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root, flush = true; } - /* - * Need to flush before releasing RCU. TODO: do it only if intermediate - * page tables were zapped; there is no need to flush under RCU protection - * if no 'struct kvm_mmu_page' is freed. - */ - if (flush) - kvm_flush_remote_tlbs_with_address(kvm, start, end - start); - rcu_read_unlock(); - return false; + /* + * Because this flow zaps _only_ leaf SPTEs, the caller doesn't need + * to provide RCU protection as no 'struct kvm_mmu_page' will be freed. + */ + return flush; } /* @@ -982,13 +959,13 @@ static bool zap_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root, * SPTEs have been cleared and a TLB flush is needed before releasing the * MMU lock. */ -bool __kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, int as_id, gfn_t start, - gfn_t end, bool can_yield, bool flush) +bool kvm_tdp_mmu_zap_leafs(struct kvm *kvm, int as_id, gfn_t start, gfn_t end, + bool can_yield, bool flush) { struct kvm_mmu_page *root; for_each_tdp_mmu_root_yield_safe(kvm, root, as_id) - flush = zap_gfn_range(kvm, root, start, end, can_yield, flush); + flush = tdp_mmu_zap_leafs(kvm, root, start, end, can_yield, flush); return flush; } @@ -1236,8 +1213,8 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) bool kvm_tdp_mmu_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range, bool flush) { - return __kvm_tdp_mmu_zap_gfn_range(kvm, range->slot->as_id, range->start, - range->end, range->may_block, flush); + return kvm_tdp_mmu_zap_leafs(kvm, range->slot->as_id, range->start, + range->end, range->may_block, flush); } typedef bool (*tdp_handler_t)(struct kvm *kvm, struct tdp_iter *iter, diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h index 6479265..c163f7c 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.h +++ b/arch/x86/kvm/mmu/tdp_mmu.h @@ -15,14 +15,8 @@ __must_check static inline bool kvm_tdp_mmu_get_root(struct kvm_mmu_page *root) void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root, bool shared); -bool __kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, int as_id, gfn_t start, +bool kvm_tdp_mmu_zap_leafs(struct kvm *kvm, int as_id, gfn_t start, gfn_t end, bool can_yield, bool flush); -static inline bool kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, int as_id, - gfn_t start, gfn_t end, bool flush) -{ - return __kvm_tdp_mmu_zap_gfn_range(kvm, as_id, start, end, true, flush); -} - bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp); void kvm_tdp_mmu_zap_all(struct kvm *kvm); void kvm_tdp_mmu_invalidate_all_roots(struct kvm *kvm); -- 2.7.4