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KVM: arm64: nv: Fully update VNCR fixmap state in kvm_translate_vncr()

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kvm_translate_vncr() first invalidates the pseudo-TLB entry and
corresponding fixmap in anticipation of installing a new translation.

While the fixmap invalidation does clear the mapping from host stage-1,
it does not clear the L1_VNCR_MAPPED flag. Depending on the state of the
VNCR TLB at vcpu_put(), this could potentially precipitate a BUG_ON() if
vt->cpu is reset.

Share a helper with kvm_vcpu_put_hw_mmu(), ensuring that KVM's view of
the VNCR fixmap is in sync with the state of the VNCR TLB. Give it a
slightly verbose name to make it obvious that it is meant to be used
local to a CPU, unlike other VNCR TLB maintenance.

Fixes: 069a05e535 ("KVM: arm64: nv: Handle VNCR_EL2-triggered faults")
Signed-off-by: Oliver Upton <oupton@kernel.org>
Link: https://patch.msgid.link/20260602235450.103057-3-oupton@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Oliver Upton 2026-06-02 16:54:47 -07:00 committed by Marc Zyngier
parent 9f76b039a7
commit 5949004d70
1 changed files with 17 additions and 10 deletions
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27
arch/arm64/kvm/nested.c
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@ -797,18 +797,24 @@ void kvm_vcpu_load_hw_mmu(struct kvm_vcpu *vcpu)
}
}
static void this_cpu_reset_vncr_fixmap(struct kvm_vcpu *vcpu)
{
if (!host_data_test_flag(L1_VNCR_MAPPED))
return;
BUG_ON(vcpu->arch.vncr_tlb->cpu != smp_processor_id());
BUG_ON(is_hyp_ctxt(vcpu));
clear_fixmap(vncr_fixmap(vcpu->arch.vncr_tlb->cpu));
vcpu->arch.vncr_tlb->cpu = -1;
host_data_clear_flag(L1_VNCR_MAPPED);
atomic_dec(&vcpu->kvm->arch.vncr_map_count);
}
void kvm_vcpu_put_hw_mmu(struct kvm_vcpu *vcpu)
{
/* Unconditionally drop the VNCR mapping if we have one */
if (host_data_test_flag(L1_VNCR_MAPPED)) {
BUG_ON(vcpu->arch.vncr_tlb->cpu != smp_processor_id());
BUG_ON(is_hyp_ctxt(vcpu));
clear_fixmap(vncr_fixmap(vcpu->arch.vncr_tlb->cpu));
vcpu->arch.vncr_tlb->cpu = -1;
host_data_clear_flag(L1_VNCR_MAPPED);
atomic_dec(&vcpu->kvm->arch.vncr_map_count);
}
this_cpu_reset_vncr_fixmap(vcpu);
/*
* Keep a reference on the associated stage-2 MMU if the vCPU is
@ -1282,7 +1288,8 @@ static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)
* We also prepare the next walk wilst we're at it.
*/
scoped_guard(write_lock, &vcpu->kvm->mmu_lock) {
invalidate_vncr(vt);
this_cpu_reset_vncr_fixmap(vcpu);
vt->valid = false;
vt->wi = (struct s1_walk_info) {
.regime = TR_EL20,