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KVM: arm64: nv: Delay freeing of shadow S2 structures until VM destruction

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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: 4f128f8e1a ("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>
This commit is contained in:
Marc Zyngier 2026-09-11 17:22:03 +01:00 committed by Oliver Upton
parent 33346f8960
commit e5843f4eff
3 changed files with 13 additions and 7 deletions
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1
arch/arm64/include/asm/kvm_nested.h
View File

@ -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);

4
arch/arm64/kvm/arm.c
View File

@ -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);
}

15
arch/arm64/kvm/nested.c
View File

@ -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);
}