Linux kernel -stable discussions
 help / color / mirror / Atom feed
* FAILED: patch "[PATCH] KVM: arm64: nv: Delay freeing of shadow S2 structures until" failed to apply to 6.18-stable tree
@ 2026-09-29 11:39 gregkh
  2026-09-30 14:05 ` [PATCH 6.18.y 1/2] KVM: arm64: nv: Fix life cycle of the nested_mmus array Sasha Levin
  0 siblings, 1 reply; 3+ messages in thread
From: gregkh @ 2026-09-29 11:39 UTC (permalink / raw)
  To: maz, ljs, oupton, weilin.chang; +Cc: stable


The patch below does not apply to the 6.18-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 <stable@vger.kernel.org>.

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-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x e5843f4effaa2ffac3e789ecd4456403564961d4
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026092944-deviation-elude-f3dc@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From e5843f4effaa2ffac3e789ecd4456403564961d4 Mon Sep 17 00:00:00 2001
From: Marc Zyngier <maz@kernel.org>
Date: Fri, 11 Sep 2026 17:22:03 +0100
Subject: [PATCH] KVM: arm64: nv: Delay freeing of shadow S2 structures until
 VM destruction

We free the shadow S2 structures from kvm_arch_flush_shadow_all(), which
is a Bad Idea(tm). Freeing the page tables is fair game (this is what
this callback is for), but freeing the container that could still be
referenced by another part of the system is not great.

Instead, grow separate destructors that gets called when we tear the VM
down for good. From there, we can nuke both the individual MMUs as well
as the global array that points to them, safe in the knowledge that the
vcpus themselves have been destroyed already.

Fixes: 4f128f8e1aaac ("KVM: arm64: nv: Support multiple nested Stage-2 mmu structures")
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
Reviewed-by: Wei-Lin Chang <weilin.chang@arm.com>
Link: https://patch.msgid.link/20260911162203.1919330-3-maz@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>

diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
index 5b8edb2e8a87..586026e85903 100644
--- a/arch/arm64/include/asm/kvm_nested.h
+++ b/arch/arm64/include/asm/kvm_nested.h
@@ -67,6 +67,7 @@ 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 int kvm_init_nested(struct kvm *kvm);
+extern void kvm_destroy_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 b53219e048bd..eaf583b77193 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -282,7 +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);
+	kvm_destroy_nested(kvm);
 err_free_cpumask:
 	free_cpumask_var(kvm->arch.supported_cpus);
 err_unshare_kvm:
@@ -340,7 +340,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
 
 	kvm_unshare_hyp(kvm, kvm + 1);
 
-	kvfree(kvm->arch.nested_mmus);
+	kvm_destroy_nested(kvm);
 	kvm_arm_teardown_hypercalls(kvm);
 }
 
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 2571f177e654..b191365d97cc 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -56,6 +56,15 @@ int kvm_init_nested(struct kvm *kvm)
 	return kvm->arch.nested_mmus ? 0 : -ENOMEM;
 }
 
+void kvm_destroy_nested(struct kvm *kvm)
+{
+	for (int i = 0; i < kvm->arch.nested_mmus_size; i+= S2_MMU_PER_VCPU)
+		kvfree(kvm->arch.nested_mmus[i]);
+
+	kvm->arch.nested_mmus_size = 0;
+	kvfree(kvm->arch.nested_mmus);
+}
+
 static int init_nested_s2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu)
 {
 	/*
@@ -1322,16 +1331,12 @@ void kvm_nested_s2_flush(struct kvm *kvm)
 
 void kvm_arch_flush_shadow_all(struct kvm *kvm)
 {
-	for (int i = kvm->arch.nested_mmus_size - 1; i >= 0; i--) {
+	for (int i = 0; i < kvm->arch.nested_mmus_size; 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);
 	}
-	kvm->arch.nested_mmus_size = 0;
 	kvm_uninit_stage2_mmu(kvm);
 }
 


^ permalink raw reply related	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2026-09-30 14:05 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-09-29 11:39 FAILED: patch "[PATCH] KVM: arm64: nv: Delay freeing of shadow S2 structures until" failed to apply to 6.18-stable tree gregkh
2026-09-30 14:05 ` [PATCH 6.18.y 1/2] KVM: arm64: nv: Fix life cycle of the nested_mmus array Sasha Levin
2026-09-30 14:05   ` [PATCH 6.18.y 2/2] KVM: arm64: nv: Delay freeing of shadow S2 structures until VM destruction Sasha Levin

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox