[PATCH 2/7] KVM: arm64: Reject the stage-2 flush hypercalls under pKVM

[Fuad Tabba]

The stage-2 TLB and context flush hypercalls remain callable once pKVM
has finalised, and five of the six dereference a host-supplied
struct kvm_s2_mmu pointer. Under pKVM none has a valid caller: the host
walks no guest stage-2, its TLB flushes go through the handle-based
__pkvm_tlb_flush_vmid, and kvm_arch_vcpu_load() skips both the VMID
update and the CPU context flush.

Move them into the band the dispatcher rejects once pKVM has finalised.

Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
Closes: https://lore.kernel.org/all/20260914130152.F0D5F1F000FF@xxxxxxxxxxxxxxx/
Signed-off-by: Fuad Tabba <fuad.tabba@xxxxxxxxx>
---
 arch/arm64/include/asm/kvm_asm.h   | 12 ++++++------
 arch/arm64/kvm/hyp/nvhe/hyp-main.c | 11 ++++++-----
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index ea319c496bb26..b182c908c1a98 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -64,6 +64,12 @@ enum __kvm_host_smccc_func {
 	__KVM_HOST_SMCCC_FUNC___vgic_v3_get_gic_config,
 	__KVM_HOST_SMCCC_FUNC___vgic_v5_save_apr,
 	__KVM_HOST_SMCCC_FUNC___vgic_v5_restore_vmcr_apr,
+	__KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context,
+	__KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa,
+	__KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa_nsh,
+	__KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid,
+	__KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_range,
+	__KVM_HOST_SMCCC_FUNC___kvm_flush_cpu_context,
 
 	MARKER(__KVM_HOST_SMCCC_FUNC_MIN_PKVM),
 
@@ -72,12 +78,6 @@ enum __kvm_host_smccc_func {
 	/* Hypercalls that are always available and common to [nh]VHE/pKVM. */
 	__KVM_HOST_SMCCC_FUNC___kvm_adjust_pc,
 	__KVM_HOST_SMCCC_FUNC___kvm_vcpu_run,
-	__KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context,
-	__KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa,
-	__KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa_nsh,
-	__KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid,
-	__KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_range,
-	__KVM_HOST_SMCCC_FUNC___kvm_flush_cpu_context,
 	__KVM_HOST_SMCCC_FUNC___kvm_timer_set_cntvoff,
 	__KVM_HOST_SMCCC_FUNC___tracing_load,
 	__KVM_HOST_SMCCC_FUNC___tracing_unload,
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 7c939baf9c1ba..b2657a3c65b40 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -913,16 +913,16 @@ static const hcall_t host_hcall[] = {
 	HANDLE_FUNC(__vgic_v3_get_gic_config),
 	HANDLE_FUNC(__vgic_v5_save_apr),
 	HANDLE_FUNC(__vgic_v5_restore_vmcr_apr),
-	HANDLE_FUNC(__pkvm_prot_finalize),
-
-	HANDLE_FUNC(__kvm_adjust_pc),
-	HANDLE_FUNC(__kvm_vcpu_run),
 	HANDLE_FUNC(__kvm_flush_vm_context),
 	HANDLE_FUNC(__kvm_tlb_flush_vmid_ipa),
 	HANDLE_FUNC(__kvm_tlb_flush_vmid_ipa_nsh),
 	HANDLE_FUNC(__kvm_tlb_flush_vmid),
 	HANDLE_FUNC(__kvm_tlb_flush_vmid_range),
 	HANDLE_FUNC(__kvm_flush_cpu_context),
+	HANDLE_FUNC(__pkvm_prot_finalize),
+
+	HANDLE_FUNC(__kvm_adjust_pc),
+	HANDLE_FUNC(__kvm_vcpu_run),
 	HANDLE_FUNC(__kvm_timer_set_cntvoff),
 	HANDLE_FUNC(__tracing_load),
 	HANDLE_FUNC(__tracing_unload),
@@ -969,7 +969,8 @@ static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
 
 	/*
 	 * If pKVM has been initialised then reject any calls to the
-	 * early "privileged" hypercalls. Note that we cannot reject
+	 * early "privileged" hypercalls, and to the ones the host has no
+	 * use for in protected mode. Note that we cannot reject
 	 * calls to __pkvm_prot_finalize for two reasons: (1) The static
 	 * key used to determine initialisation must be toggled prior to
 	 * finalisation and (2) finalisation is performed on a per-CPU
-- 
2.39.5