From: Yan Zhao Date: Tue, 18 Mar 2025 01:33:33 +0000 (+0800) Subject: KVM: x86/mmu: Check and free obsolete roots in kvm_mmu_reload() X-Git-Tag: v6.15-rc6~1^2^2~3 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=20a6cff3b283f0601048ace87ad1bc89627e36f2;p=thirdparty%2Fkernel%2Flinux.git KVM: x86/mmu: Check and free obsolete roots in kvm_mmu_reload() Check request KVM_REQ_MMU_FREE_OBSOLETE_ROOTS to free obsolete roots in kvm_mmu_reload() to prevent kvm_mmu_reload() from seeing a stale obsolete root. Since kvm_mmu_reload() can be called outside the vcpu_enter_guest() path (e.g., kvm_arch_vcpu_pre_fault_memory()), it may be invoked after a root has been marked obsolete and before vcpu_enter_guest() is invoked to process KVM_REQ_MMU_FREE_OBSOLETE_ROOTS and set root.hpa to invalid. This causes kvm_mmu_reload() to fail to load a new root, which can lead to kvm_arch_vcpu_pre_fault_memory() being stuck in the while loop in kvm_tdp_map_page() since RET_PF_RETRY is always returned due to is_page_fault_stale(). Keep the existing check of KVM_REQ_MMU_FREE_OBSOLETE_ROOTS in vcpu_enter_guest() since the cost of kvm_check_request() is negligible, especially a check that's guarded by kvm_request_pending(). Export symbol of kvm_mmu_free_obsolete_roots() as kvm_mmu_reload() is inline and may be called outside of kvm.ko. Fixes: 6e01b7601dfe ("KVM: x86: Implement kvm_arch_vcpu_pre_fault_memory()") Suggested-by: Sean Christopherson Signed-off-by: Yan Zhao Link: https://lore.kernel.org/r/20250318013333.5817-1-yan.y.zhao@intel.com Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index 050a0e229a4d1..f2b36d32ef40e 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -104,6 +104,9 @@ void kvm_mmu_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new, static inline int kvm_mmu_reload(struct kvm_vcpu *vcpu) { + if (kvm_check_request(KVM_REQ_MMU_FREE_OBSOLETE_ROOTS, vcpu)) + kvm_mmu_free_obsolete_roots(vcpu); + /* * Checking root.hpa is sufficient even when KVM has mirror root. * We can have either: diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 63bb77ee1bb16..387464ebe8e8d 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -5974,6 +5974,7 @@ void kvm_mmu_free_obsolete_roots(struct kvm_vcpu *vcpu) __kvm_mmu_free_obsolete_roots(vcpu->kvm, &vcpu->arch.root_mmu); __kvm_mmu_free_obsolete_roots(vcpu->kvm, &vcpu->arch.guest_mmu); } +EXPORT_SYMBOL_GPL(kvm_mmu_free_obsolete_roots); static u64 mmu_pte_write_fetch_gpte(struct kvm_vcpu *vcpu, gpa_t *gpa, int *bytes)