Commit 7e7c2cf0 authored by Fuad Tabba's avatar Fuad Tabba Committed by Marc Zyngier
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KVM: arm64: Fix ID register initialization for non-protected pKVM guests 



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: 41d6028e ("KVM: arm64: Convert the SVE guest vcpu flag to a vm flag")
Signed-off-by: default avatarFuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20260213143815.1732675-4-tabba@google.com


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent 9cb0468d

arch/arm64/kvm/hyp/nvhe/pkvm.c

+33 −2
Original line number Diff line number Diff line
@@ -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)