FAILED: patch "[PATCH] KVM: arm64: nv: Fix life cycle of the nested_mmus array" failed to apply to 7.2-stable tree

PATCH New [email protected] 2 participants 2 messages Sep 29 – Sep 30

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Stable branch arm64 KVM arm64

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[email protected]

author maintainer

2026-09-29 11:40 UTC #0 lore raw

The patch below does not apply to the 7.2-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-7.2.y
git checkout FETCH_HEAD
git cherry-pick -x 33346f8960c7bb6a3b4e273b5cfe25c5a8be349f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026092948-velocity-mandatory-1d5d@gregkh' --subject-prefix 'PATCH 7.2.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 33346f8960c7bb6a3b4e273b5cfe25c5a8be349f Mon Sep 17 00:00:00 2001
From: Marc Zyngier <[email protected]>
Date: Fri, 11 Sep 2026 17:22:02 +0100
Subject: [PATCH] KVM: arm64: nv: Fix life cycle of the nested_mmus array

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 <[email protected]>

Reported-by Karl Mehltretter <[email protected]>

Acked-by Lorenzo Stoakes (ARM) <[email protected]>

Link https://lore.kernel.org/r/[email protected] open here

Signed-off-by Marc Zyngier <[email protected]>

Cc [email protected]

Reviewed-by Wei-Lin Chang <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Oliver Upton <[email protected]>

arch/arm64/include/asm/kvm_host.h +1 -1

index 27fe0cd5b2d7..cd9b9d2462f9 100644
@@ -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;

arch/arm64/include/asm/kvm_nested.h +1 -1

index 1ed708335809..5b8edb2e8a87 100644
@@ -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);

arch/arm64/kvm/arm.c +6 -2

index 8b080804bc90..b53219e048bd 100644
@@ -236,8 +236,6 @@ 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;

@@ -252,6 +250,10 @@ 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

@@ -280,6 +282,7 @@ 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:

@@ -337,6 +340,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
 
 	kvm_unshare_hyp(kvm, kvm + 1);
 
+	kvfree(kvm->arch.nested_mmus);
 	kvm_arm_teardown_hypercalls(kvm);
 }

arch/arm64/kvm/nested.c +43 ~~-50~~

171 lines not on this page · raw message

Sasha Levin

maintainer

2026-09-30 12:55 UTC #1 lore raw

PATCH 1/1 KVM: arm64: nv: Fix life cycle of the nested_mmus array

From: Marc Zyngier <[email protected]>

[ Upstream commit 33346f8960c7bb6a3b4e273b5cfe25c5a8be349f ]