From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E9A31432300; Fri, 14 Aug 2026 10:33:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786703616; cv=none; b=Dn2oA7EyUiA7nnIVHERFZf8johO3qAzdmyNXK6aavtixnTQllCKcskCazukJu6lI2oCWyASo2W1c3b5fpIwO4It3aH1KsoKXKwMCwiPttsSAhDvgtmwlUJAa6ChQlM4RARP021BM1kSBPt0MsY/jmvRUEJ6DDioIiT8Ke9BEUmw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786703616; c=relaxed/simple; bh=nxbosSKl4RxPMsHhC+qMYOSPlIAMgue7GUeeiPEzNjg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RVCt0UkNpR4nuGe3q2anN9HH+w31dei1i6/lIEIl/go4kK7jJKFZceaDczyMAT09s2ifLeQG9v8V3EvbQyWRUZtH2xeT0E1+rlLPTS4F5z1RaWmcdW9zByWIn4Cn0L52gP84DSAgPLaOmTtNVPcm40v5f16Y1t93HyYCjh2qA3U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KOM8dR91; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KOM8dR91" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 160231F000E9; Fri, 14 Aug 2026 10:33:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786703606; bh=eewShcqktqgmf6r6xOdy7z1RVsji+aevL+ysnFGF1Q4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=KOM8dR9163F6Xt+qCyK3IyQFWoIyLV/1j+Dgqy5Ht2x/qaCIKTYp8puIl4MXc45VV fpC4+01qhy09qKhiLkmZenox5pW6jV5dAvSQK/r7lwHFJedAVOiV0wArf4R9k1HXrH Q1j1X5iEJn4MpmkIVoduRY/zrsz3freEDEfKg8KRMYT87gNmnsMw7sQ6M3k7C+Eu6L WiuaMwNQ6NfivHt5ITAXrmuyWf+nbY+ULSHOjLuqB2e0XHlJlKvWk7gMgmG89xH5RM fKQCJ30/UMn9UG74EhZSpAJ3BbtBKo73miv8bJbRHC2Xv2F1SesjgK8UR4Pa7WvuQI ed5LhnqCkFF5w== Received: from sofa.misterjones.org ([185.219.108.64] helo=valley-girl.lan) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1wupE4-0000000FdQO-00AX; Fri, 14 Aug 2026 10:33:24 +0000 From: Marc Zyngier To: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org Cc: Steffen Eiden , Joey Gouly , Suzuki K Poulose , Oliver Upton , Zenghui Yu , Fuad Tabba , ljs@kernel.org, Shen Yongchao , Karl Mehltretter , Wei-Lin Chang , stable@vger.kernel.org Subject: [PATCH v2 1/2] KVM: arm64: nv: Fix life cycle of the nested_mmus array Date: Fri, 14 Aug 2026 11:32:29 +0100 Message-ID: <20260814103230.858578-2-maz@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260814103230.858578-1-maz@kernel.org> References: <20260814103230.858578-1-maz@kernel.org> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, seiden@linux.ibm.com, joey.gouly@arm.com, suzuki.poulose@arm.com, oupton@kernel.org, yuzenghui@huawei.com, fuad.tabba@linux.dev, ljs@kernel.org, grayhat@foxmail.com, kmehltretter@gmail.com, weilin.chang@arm.com, stable@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false The nested_mmus array holds the shadow page tables that are used when a guest is running a nested context. These structures are allocated on VCPU_INIT for whole guest, which implies that they may have to be relocated as the array grows. Should a VCPU_INIT occur whilst a vcpu is actively running an L2 and that the allocation requires relocation, that vcpu will still be running with a pointer to the previous structure, which will have been freed. Fix this by turning the array of structures to an array of pointers, which is now allocated at VM creation, sized to the absolute maximum that KVM can handle. In turn, each VCPU_INIT contributes S2_MMU_PER_VCPU to the pool. No reallocation is ever performed, and the life cycle of each object is much clearer: - the nested_mmus array is allocated in kvm_init_nested(), and freed in kvm_arch_destroy_vm() - s2_mmu structures are allocated in kvm_vcpu_init_nested(), and freed on kvm_arch_flush_shadow_all() Finally, the freeing of vcpu->arch.vncr_array is made consistent rather than being done on some failure paths, but not others. Fixes: 4f128f8e1aaa ("KVM: arm64: nv: Support multiple nested Stage-2 mmu structures") Reported-by: Shen Yongchao Reported-by: Karl Mehltretter Suggested-by: Karl Mehltretter Link: https://lore.kernel.org/r/20260803224405.41468-1-kmehltretter@gmail.com Signed-off-by: Marc Zyngier Cc: stable@vger.kernel.org --- arch/arm64/include/asm/kvm_host.h | 2 +- arch/arm64/include/asm/kvm_nested.h | 2 +- arch/arm64/kvm/arm.c | 8 ++- arch/arm64/kvm/nested.c | 93 +++++++++++++---------------- 4 files changed, 51 insertions(+), 54 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 108966a9db12b..08b2f24dc3c79 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -322,7 +322,7 @@ struct kvm_arch { * Stage 2 paging state for VMs with nested S2 using a virtual * VMID. */ - struct kvm_s2_mmu *nested_mmus; + struct kvm_s2_mmu **nested_mmus; size_t nested_mmus_size; int nested_mmus_next; diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h index 1ed7083358096..5b8edb2e8a87d 100644 --- a/arch/arm64/include/asm/kvm_nested.h +++ b/arch/arm64/include/asm/kvm_nested.h @@ -66,7 +66,7 @@ static inline u64 translate_ttbr0_el2_to_ttbr0_el1(u64 ttbr0) extern bool forward_smc_trap(struct kvm_vcpu *vcpu); extern bool forward_debug_exception(struct kvm_vcpu *vcpu); -extern void kvm_init_nested(struct kvm *kvm); +extern int kvm_init_nested(struct kvm *kvm); extern int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu); extern void kvm_init_nested_s2_mmu(struct kvm_s2_mmu *mmu); extern struct kvm_s2_mmu *lookup_s2_mmu(struct kvm_vcpu *vcpu); diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 50adfff75be82..7607173c1a40c 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -223,8 +223,6 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) mutex_unlock(&kvm->lock); #endif - kvm_init_nested(kvm); - ret = kvm_share_hyp(kvm, kvm + 1); if (ret) return ret; @@ -239,6 +237,10 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) if (ret) goto err_free_cpumask; + ret = kvm_init_nested(kvm); + if (ret) + goto err_uninit_mmu; + if (is_protected_kvm_enabled()) { /* * If any failures occur after this is successful, make sure to @@ -267,6 +269,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) err_uninit_mmu: kvm_uninit_stage2_mmu(kvm); + kvfree(kvm->arch.nested_mmus); err_free_cpumask: free_cpumask_var(kvm->arch.supported_cpus); err_unshare_kvm: @@ -324,6 +327,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm) kvm_unshare_hyp(kvm, kvm + 1); + kvfree(kvm->arch.nested_mmus); kvm_arm_teardown_hypercalls(kvm); } diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index 20af94197a8a7..254cbd8703b3d 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -44,11 +44,15 @@ struct vncr_tlb { */ #define S2_MMU_PER_VCPU 2 -void kvm_init_nested(struct kvm *kvm) +int kvm_init_nested(struct kvm *kvm) { - kvm->arch.nested_mmus = NULL; + kvm->arch.nested_mmus = kvmalloc_array(KVM_MAX_VCPUS * S2_MMU_PER_VCPU, + sizeof(struct s2_mmu *), + GFP_KERNEL_ACCOUNT); kvm->arch.nested_mmus_size = 0; atomic_set(&kvm->arch.vncr_tlb_count, 0); + + return kvm->arch.nested_mmus ? 0 : -ENOMEM; } static int init_nested_s2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu) @@ -69,8 +73,9 @@ static int init_nested_s2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu) int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu) { struct kvm *kvm = vcpu->kvm; - struct kvm_s2_mmu *tmp; - int num_mmus, ret = 0; + int num_mmus; + + lockdep_assert_held(&kvm->arch.config_lock); if (test_bit(KVM_ARM_VCPU_HAS_EL2_E2H0, kvm->arch.vcpu_features) && !cpus_have_final_cap(ARM64_HAS_HCR_NV1)) @@ -83,51 +88,40 @@ int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu) if (!vcpu->arch.ctxt.vncr_array) return -ENOMEM; - /* - * Let's treat memory allocation failures as benign: If we fail to - * allocate anything, return an error and keep the allocated array - * alive. Userspace may try to recover by initializing the vcpu - * again, and there is no reason to affect the whole VM for this. - */ num_mmus = atomic_read(&kvm->online_vcpus) * S2_MMU_PER_VCPU; if (num_mmus > kvm->arch.nested_mmus_size) { - tmp = kvcalloc(num_mmus, sizeof(*tmp), GFP_KERNEL_ACCOUNT); + struct kvm_s2_mmu *tmp; + int i, ret = 0; + + tmp = kvcalloc(S2_MMU_PER_VCPU, sizeof(*tmp), GFP_KERNEL_ACCOUNT); if (!tmp) - return -ENOMEM; + ret = -ENOMEM; - write_lock(&kvm->mmu_lock); - - if (kvm->arch.nested_mmus_size) { - memcpy(tmp, kvm->arch.nested_mmus, - size_mul(sizeof(*tmp), kvm->arch.nested_mmus_size)); - - for (int i = 0; i < kvm->arch.nested_mmus_size; i++) - tmp[i].pgt->mmu = &tmp[i]; + for (i = 0; !ret && i < S2_MMU_PER_VCPU; i++) { + ret = init_nested_s2_mmu(kvm, &tmp[i]); + if (ret) + break; } - swap(kvm->arch.nested_mmus, tmp); + if (ret) { + while (--i >= 0) + kvm_free_stage2_pgd(&tmp[i]); - write_unlock(&kvm->mmu_lock); + kvfree(tmp); + free_page((unsigned long)vcpu->arch.ctxt.vncr_array); + vcpu->arch.ctxt.vncr_array = NULL; + return ret; + } + + guard(write_lock)(&kvm->mmu_lock); - kvfree(tmp); + for (i = 0; i < S2_MMU_PER_VCPU; i++) + kvm->arch.nested_mmus[i + kvm->arch.nested_mmus_size] = &tmp[i]; + + kvm->arch.nested_mmus_size += S2_MMU_PER_VCPU; } - for (int i = kvm->arch.nested_mmus_size; !ret && i < num_mmus; i++) - ret = init_nested_s2_mmu(kvm, &kvm->arch.nested_mmus[i]); - - if (ret) { - for (int i = kvm->arch.nested_mmus_size; i < num_mmus; i++) - kvm_free_stage2_pgd(&kvm->arch.nested_mmus[i]); - - free_page((unsigned long)vcpu->arch.ctxt.vncr_array); - vcpu->arch.ctxt.vncr_array = NULL; - - return ret; - } - - kvm->arch.nested_mmus_size = num_mmus; - return 0; } @@ -741,7 +735,7 @@ void kvm_s2_mmu_iterate_by_vmid(struct kvm *kvm, u16 vmid, write_lock(&kvm->mmu_lock); for (int i = 0; i < kvm->arch.nested_mmus_size; i++) { - struct kvm_s2_mmu *mmu = &kvm->arch.nested_mmus[i]; + struct kvm_s2_mmu *mmu = kvm->arch.nested_mmus[i]; if (!kvm_s2_mmu_valid(mmu)) continue; @@ -783,7 +777,7 @@ struct kvm_s2_mmu *lookup_s2_mmu(struct kvm_vcpu *vcpu) * if S2 translation is disabled. */ for (int i = 0; i < kvm->arch.nested_mmus_size; i++) { - struct kvm_s2_mmu *mmu = &kvm->arch.nested_mmus[i]; + struct kvm_s2_mmu *mmu = kvm->arch.nested_mmus[i]; if (!kvm_s2_mmu_valid(mmu)) continue; @@ -822,7 +816,7 @@ static struct kvm_s2_mmu *get_s2_mmu_nested(struct kvm_vcpu *vcpu) for (i = kvm->arch.nested_mmus_next; i < (kvm->arch.nested_mmus_size + kvm->arch.nested_mmus_next); i++) { - s2_mmu = &kvm->arch.nested_mmus[i % kvm->arch.nested_mmus_size]; + s2_mmu = kvm->arch.nested_mmus[i % kvm->arch.nested_mmus_size]; if (atomic_read(&s2_mmu->refcnt) == 0) break; @@ -1269,7 +1263,7 @@ void kvm_nested_s2_wp(struct kvm *kvm) return; for (i = 0; i < kvm->arch.nested_mmus_size; i++) { - struct kvm_s2_mmu *mmu = &kvm->arch.nested_mmus[i]; + struct kvm_s2_mmu *mmu = kvm->arch.nested_mmus[i]; if (kvm_s2_mmu_valid(mmu)) kvm_stage2_wp_range(mmu, 0, kvm_phys_size(mmu)); @@ -1288,7 +1282,7 @@ void kvm_nested_s2_unmap(struct kvm *kvm, bool may_block) return; for (i = 0; i < kvm->arch.nested_mmus_size; i++) { - struct kvm_s2_mmu *mmu = &kvm->arch.nested_mmus[i]; + struct kvm_s2_mmu *mmu = kvm->arch.nested_mmus[i]; if (kvm_s2_mmu_valid(mmu)) kvm_stage2_unmap_range(mmu, 0, kvm_phys_size(mmu), may_block); @@ -1307,7 +1301,7 @@ void kvm_nested_s2_flush(struct kvm *kvm) return; for (i = 0; i < kvm->arch.nested_mmus_size; i++) { - struct kvm_s2_mmu *mmu = &kvm->arch.nested_mmus[i]; + struct kvm_s2_mmu *mmu = kvm->arch.nested_mmus[i]; if (kvm_s2_mmu_valid(mmu)) kvm_stage2_flush_range(mmu, 0, kvm_phys_size(mmu)); @@ -1316,16 +1310,15 @@ void kvm_nested_s2_flush(struct kvm *kvm) void kvm_arch_flush_shadow_all(struct kvm *kvm) { - int i; - - for (i = 0; i < kvm->arch.nested_mmus_size; i++) { - struct kvm_s2_mmu *mmu = &kvm->arch.nested_mmus[i]; + for (int i = kvm->arch.nested_mmus_size - 1; i >= 0; i--) { + struct kvm_s2_mmu *mmu = kvm->arch.nested_mmus[i]; if (!WARN_ON(atomic_read(&mmu->refcnt))) kvm_free_stage2_pgd(mmu); + + if ((i % S2_MMU_PER_VCPU) == 0) + kvfree(mmu); } - kvfree(kvm->arch.nested_mmus); - kvm->arch.nested_mmus = NULL; kvm->arch.nested_mmus_size = 0; kvm_uninit_stage2_mmu(kvm); } -- 2.47.3