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KVM: arm64: Fix ID register initialization for non-protected pKVM guests

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In protected mode, the hypervisor maintains a separate instance of
the `kvm` structure for each VM. For non-protected VMs, this structure is
initialized from the host's `kvm` state.

Currently, `pkvm_init_features_from_host()` copies the
`KVM_ARCH_FLAG_ID_REGS_INITIALIZED` flag from the host without the
underlying `id_regs` data being initialized. This results in the
hypervisor seeing the flag as set while the ID registers remain zeroed.

Consequently, `kvm_has_feat()` checks at EL2 fail (return 0) for
non-protected VMs. This breaks logic that relies on feature detection,
such as `ctxt_has_tcrx()` for TCR2_EL1 support. As a result, certain
system registers (e.g., TCR2_EL1, PIR_EL1, POR_EL1) are not
saved/restored during the world switch, which could lead to state
corruption.

Fix this by explicitly copying the ID registers from the host `kvm` to
the hypervisor `kvm` for non-protected VMs during initialization, since
we trust the host with its non-protected guests' features. Also ensure
`KVM_ARCH_FLAG_ID_REGS_INITIALIZED` is cleared initially in
`pkvm_init_features_from_host` so that `vm_copy_id_regs` can properly
initialize them and set the flag once done.

Fixes: 41d6028e28 ("KVM: arm64: Convert the SVE guest vcpu flag to a vm flag")
Signed-off-by: Fuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20260213143815.1732675-4-tabba@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Fuad Tabba 2026-02-13 14:38:14 +00:00 committed by Marc Zyngier
parent 9cb0468d0b
commit 7e7c2cf002
1 changed files with 33 additions and 2 deletions
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35
arch/arm64/kvm/hyp/nvhe/pkvm.c
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@ -342,6 +342,7 @@ static void pkvm_init_features_from_host(struct pkvm_hyp_vm *hyp_vm, const struc
/* No restrictions for non-protected VMs. */
if (!kvm_vm_is_protected(kvm)) {
hyp_vm->kvm.arch.flags = host_arch_flags;
hyp_vm->kvm.arch.flags &= ~BIT_ULL(KVM_ARCH_FLAG_ID_REGS_INITIALIZED);
bitmap_copy(kvm->arch.vcpu_features,
host_kvm->arch.vcpu_features,
@ -471,6 +472,35 @@ static int pkvm_vcpu_init_sve(struct pkvm_hyp_vcpu *hyp_vcpu, struct kvm_vcpu *h
return ret;
}
static int vm_copy_id_regs(struct pkvm_hyp_vcpu *hyp_vcpu)
{
struct pkvm_hyp_vm *hyp_vm = pkvm_hyp_vcpu_to_hyp_vm(hyp_vcpu);
const struct kvm *host_kvm = hyp_vm->host_kvm;
struct kvm *kvm = &hyp_vm->kvm;
if (!test_bit(KVM_ARCH_FLAG_ID_REGS_INITIALIZED, &host_kvm->arch.flags))
return -EINVAL;
if (test_and_set_bit(KVM_ARCH_FLAG_ID_REGS_INITIALIZED, &kvm->arch.flags))
return 0;
memcpy(kvm->arch.id_regs, host_kvm->arch.id_regs, sizeof(kvm->arch.id_regs));
return 0;
}
static int pkvm_vcpu_init_sysregs(struct pkvm_hyp_vcpu *hyp_vcpu)
{
int ret = 0;
if (pkvm_hyp_vcpu_is_protected(hyp_vcpu))
kvm_init_pvm_id_regs(&hyp_vcpu->vcpu);
else
ret = vm_copy_id_regs(hyp_vcpu);
return ret;
}
static int init_pkvm_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu,
struct pkvm_hyp_vm *hyp_vm,
struct kvm_vcpu *host_vcpu)
@ -490,8 +520,9 @@ static int init_pkvm_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu,
hyp_vcpu->vcpu.arch.cflags = READ_ONCE(host_vcpu->arch.cflags);
hyp_vcpu->vcpu.arch.mp_state.mp_state = KVM_MP_STATE_STOPPED;
if (pkvm_hyp_vcpu_is_protected(hyp_vcpu))
kvm_init_pvm_id_regs(&hyp_vcpu->vcpu);
ret = pkvm_vcpu_init_sysregs(hyp_vcpu);
if (ret)
goto done;
ret = pkvm_vcpu_init_traps(hyp_vcpu);
if (ret)