From 7b7e1ab6fdc554f77f98c597aa9375b52b3a5454 Mon Sep 17 00:00:00 2001 From: David Matlack Date: Wed, 19 Jan 2022 23:07:28 +0000 Subject: [PATCH] KVM: x86/mmu: Consolidate logic to atomically install a new TDP MMU page table Consolidate the logic to atomically replace an SPTE with an SPTE that points to a new page table into a single helper function. This will be used in a follow-up commit to split huge pages, which involves replacing each huge page SPTE with an SPTE that points to a page table. Opportunistically drop the call to trace_kvm_mmu_get_page() in kvm_tdp_mmu_map() since it is redundant with the identical tracepoint in tdp_mmu_alloc_sp(). No functional change intended. Reviewed-by: Peter Xu Signed-off-by: David Matlack Message-Id: <20220119230739.2234394-8-dmatlack@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu/tdp_mmu.c | 68 ++++++++++++++++++++------------------ 1 file changed, 36 insertions(+), 32 deletions(-) diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index f630ec4a68bd..bcba4adbafac 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -268,24 +268,6 @@ static void handle_changed_spte_dirty_log(struct kvm *kvm, int as_id, gfn_t gfn, } } -/** - * tdp_mmu_link_sp() - Add a new shadow page to the list of used pages - * - * @kvm: kvm instance - * @sp: the new page - * @account_nx: This page replaces a NX large page and should be marked for - * eventual reclaim. - */ -static void tdp_mmu_link_sp(struct kvm *kvm, struct kvm_mmu_page *sp, - bool account_nx) -{ - spin_lock(&kvm->arch.tdp_mmu_pages_lock); - list_add(&sp->link, &kvm->arch.tdp_mmu_pages); - if (account_nx) - account_huge_nx_page(kvm, sp); - spin_unlock(&kvm->arch.tdp_mmu_pages_lock); -} - /** * tdp_mmu_unlink_sp() - Remove a shadow page from the list of used pages * @@ -979,6 +961,38 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu, return ret; } +/* + * tdp_mmu_link_sp_atomic - Atomically replace the given spte with an spte + * pointing to the provided page table. + * + * @kvm: kvm instance + * @iter: a tdp_iter instance currently on the SPTE that should be set + * @sp: The new TDP page table to install. + * @account_nx: True if this page table is being installed to split a + * non-executable huge page. + * + * Returns: 0 if the new page table was installed. Non-0 if the page table + * could not be installed (e.g. the atomic compare-exchange failed). + */ +static int tdp_mmu_link_sp_atomic(struct kvm *kvm, struct tdp_iter *iter, + struct kvm_mmu_page *sp, bool account_nx) +{ + u64 spte = make_nonleaf_spte(sp->spt, !shadow_accessed_mask); + int ret; + + ret = tdp_mmu_set_spte_atomic(kvm, iter, spte); + if (ret) + return ret; + + spin_lock(&kvm->arch.tdp_mmu_pages_lock); + list_add(&sp->link, &kvm->arch.tdp_mmu_pages); + if (account_nx) + account_huge_nx_page(kvm, sp); + spin_unlock(&kvm->arch.tdp_mmu_pages_lock); + + return 0; +} + /* * Handle a TDP page fault (NPT/EPT violation/misconfiguration) by installing * page tables and SPTEs to translate the faulting guest physical address. @@ -988,8 +1002,6 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) struct kvm_mmu *mmu = vcpu->arch.mmu; struct tdp_iter iter; struct kvm_mmu_page *sp; - u64 *child_pt; - u64 new_spte; int ret; kvm_mmu_hugepage_adjust(vcpu, fault); @@ -1024,6 +1036,9 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) } if (!is_shadow_present_pte(iter.old_spte)) { + bool account_nx = fault->huge_page_disallowed && + fault->req_level >= iter.level; + /* * If SPTE has been frozen by another thread, just * give up and retry, avoiding unnecessary page table @@ -1033,18 +1048,7 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) break; sp = tdp_mmu_alloc_sp(vcpu, iter.gfn, iter.level - 1); - child_pt = sp->spt; - - new_spte = make_nonleaf_spte(child_pt, - !shadow_accessed_mask); - - if (!tdp_mmu_set_spte_atomic(vcpu->kvm, &iter, new_spte)) { - tdp_mmu_link_sp(vcpu->kvm, sp, - fault->huge_page_disallowed && - fault->req_level >= iter.level); - - trace_kvm_mmu_get_page(sp, true); - } else { + if (tdp_mmu_link_sp_atomic(vcpu->kvm, &iter, sp, account_nx)) { tdp_mmu_free_sp(sp); break; } -- 2.39.5