[PATCH v3 06/36] KVM: arm64: Remove is_protected_kvm_enabled() checks from hypercalls

Will Deacon
2026-03-05T14:44:31Z

When pKVM is not enabled, the host shouldn't issue pKVM-specific
hypercalls and so there's no point checking for this in the pKVM
hypercall handlers.

Remove the redundant is_protected_kvm_enabled() checks from each
hypercall and instead rejig the hypercall table so that the
pKVM-specific hypercalls are unreachable when pKVM is not being used.

Reviewed-by: Quentin Perret <qperret@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/include/asm/kvm_asm.h | 24 +++++++-----
arch/arm64/kvm/hyp/nvhe/hyp-main.c | 63 ++++++++++--------------------
2 files changed, 34 insertions(+), 53 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index a1ad12c72ebf..7b72aac4730d 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -51,7 +51,7 @@
#include <linux/mm.h>

enum __kvm_host_smccc_func {
- /* Hypercalls available only prior to pKVM finalisation */
+ /* Hypercalls that are unavailable once pKVM has finalised. */
/* __KVM_HOST_SMCCC_FUNC___kvm_hyp_init */
__KVM_HOST_SMCCC_FUNC___pkvm_init = __KVM_HOST_SMCCC_FUNC___kvm_hyp_init + 1,
__KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping,
@@ -60,16 +60,9 @@ enum __kvm_host_smccc_func {
__KVM_HOST_SMCCC_FUNC___vgic_v3_init_lrs,
__KVM_HOST_SMCCC_FUNC___vgic_v3_get_gic_config,
__KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize,
+ __KVM_HOST_SMCCC_FUNC_MIN_PKVM = __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize,

- /* Hypercalls available after pKVM finalisation */
- __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp,
- __KVM_HOST_SMCCC_FUNC___pkvm_host_unshare_hyp,
- __KVM_HOST_SMCCC_FUNC___pkvm_host_share_guest,
- __KVM_HOST_SMCCC_FUNC___pkvm_host_unshare_guest,
- __KVM_HOST_SMCCC_FUNC___pkvm_host_relax_perms_guest,
- __KVM_HOST_SMCCC_FUNC___pkvm_host_wrprotect_guest,
- __KVM_HOST_SMCCC_FUNC___pkvm_host_test_clear_young_guest,
- __KVM_HOST_SMCCC_FUNC___pkvm_host_mkyoung_guest,
+ /* 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,
@@ -81,6 +74,17 @@ enum __kvm_host_smccc_func {
__KVM_HOST_SMCCC_FUNC___kvm_timer_set_cntvoff,
__KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs,
__KVM_HOST_SMCCC_FUNC___vgic_v3_restore_vmcr_aprs,
+ __KVM_HOST_SMCCC_FUNC_MAX_NO_PKVM = __KVM_HOST_SMCCC_FUNC___vgic_v3_restore_vmcr_aprs,
+
+ /* Hypercalls that are available only when pKVM has finalised. */
+ __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp,
+ __KVM_HOST_SMCCC_FUNC___pkvm_host_unshare_hyp,
+ __KVM_HOST_SMCCC_FUNC___pkvm_host_share_guest,
+ __KVM_HOST_SMCCC_FUNC___pkvm_host_unshare_guest,
+ __KVM_HOST_SMCCC_FUNC___pkvm_host_relax_perms_guest,
+ __KVM_HOST_SMCCC_FUNC___pkvm_host_wrprotect_guest,
+ __KVM_HOST_SMCCC_FUNC___pkvm_host_test_clear_young_guest,
+ __KVM_HOST_SMCCC_FUNC___pkvm_host_mkyoung_guest,
__KVM_HOST_SMCCC_FUNC___pkvm_reserve_vm,
__KVM_HOST_SMCCC_FUNC___pkvm_unreserve_vm,
__KVM_HOST_SMCCC_FUNC___pkvm_init_vm,
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index e7790097db93..127decc2dd2b 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -169,9 +169,6 @@ static void handle___pkvm_vcpu_load(struct kvm_cpu_context *host_ctxt)
DECLARE_REG(u64, hcr_el2, host_ctxt, 3);
struct pkvm_hyp_vcpu *hyp_vcpu;

- if (!is_protected_kvm_enabled())
- return;
-
hyp_vcpu = pkvm_load_hyp_vcpu(handle, vcpu_idx);
if (!hyp_vcpu)
return;
@@ -188,12 +185,8 @@ static void handle___pkvm_vcpu_load(struct kvm_cpu_context *host_ctxt)

static void handle___pkvm_vcpu_put(struct kvm_cpu_context *host_ctxt)
{
- struct pkvm_hyp_vcpu *hyp_vcpu;
+ struct pkvm_hyp_vcpu *hyp_vcpu = pkvm_get_loaded_hyp_vcpu();

- if (!is_protected_kvm_enabled())
- return;
-
- hyp_vcpu = pkvm_get_loaded_hyp_vcpu();
if (hyp_vcpu)
pkvm_put_hyp_vcpu(hyp_vcpu);
}
@@ -257,9 +250,6 @@ static void handle___pkvm_host_share_guest(struct kvm_cpu_context *host_ctxt)
struct pkvm_hyp_vcpu *hyp_vcpu;
int ret = -EINVAL;

- if (!is_protected_kvm_enabled())
- goto out;
-
hyp_vcpu = pkvm_get_loaded_hyp_vcpu();
if (!hyp_vcpu || pkvm_hyp_vcpu_is_protected(hyp_vcpu))
goto out;
@@ -281,9 +271,6 @@ static void handle___pkvm_host_unshare_guest(struct kvm_cpu_context *host_ctxt)
struct pkvm_hyp_vm *hyp_vm;
int ret = -EINVAL;

- if (!is_protected_kvm_enabled())
- goto out;
-
hyp_vm = get_np_pkvm_hyp_vm(handle);
if (!hyp_vm)
goto out;
@@ -301,9 +288,6 @@ static void handle___pkvm_host_relax_perms_guest(struct kvm_cpu_context *host_ct
struct pkvm_hyp_vcpu *hyp_vcpu;
int ret = -EINVAL;

- if (!is_protected_kvm_enabled())
- goto out;
-
hyp_vcpu = pkvm_get_loaded_hyp_vcpu();
if (!hyp_vcpu || pkvm_hyp_vcpu_is_protected(hyp_vcpu))
goto out;
@@ -321,9 +305,6 @@ static void handle___pkvm_host_wrprotect_guest(struct kvm_cpu_context *host_ctxt
struct pkvm_hyp_vm *hyp_vm;
int ret = -EINVAL;

- if (!is_protected_kvm_enabled())
- goto out;
-
hyp_vm = get_np_pkvm_hyp_vm(handle);
if (!hyp_vm)
goto out;
@@ -343,9 +324,6 @@ static void handle___pkvm_host_test_clear_young_guest(struct kvm_cpu_context *ho
struct pkvm_hyp_vm *hyp_vm;
int ret = -EINVAL;

- if (!is_protected_kvm_enabled())
- goto out;
-
hyp_vm = get_np_pkvm_hyp_vm(handle);
if (!hyp_vm)
goto out;
@@ -362,9 +340,6 @@ static void handle___pkvm_host_mkyoung_guest(struct kvm_cpu_context *host_ctxt)
struct pkvm_hyp_vcpu *hyp_vcpu;
int ret = -EINVAL;

- if (!is_protected_kvm_enabled())
- goto out;
-
hyp_vcpu = pkvm_get_loaded_hyp_vcpu();
if (!hyp_vcpu || pkvm_hyp_vcpu_is_protected(hyp_vcpu))
goto out;
@@ -424,12 +399,8 @@ static void handle___kvm_tlb_flush_vmid(struct kvm_cpu_context *host_ctxt)
static void handle___pkvm_tlb_flush_vmid(struct kvm_cpu_context *host_ctxt)
{
DECLARE_REG(pkvm_handle_t, handle, host_ctxt, 1);
- struct pkvm_hyp_vm *hyp_vm;
+ struct pkvm_hyp_vm *hyp_vm = get_np_pkvm_hyp_vm(handle);

- if (!is_protected_kvm_enabled())
- return;
-
- hyp_vm = get_np_pkvm_hyp_vm(handle);
if (!hyp_vm)
return;

@@ -603,14 +574,6 @@ static const hcall_t host_hcall[] = {
HANDLE_FUNC(__vgic_v3_get_gic_config),
HANDLE_FUNC(__pkvm_prot_finalize),

- HANDLE_FUNC(__pkvm_host_share_hyp),
- HANDLE_FUNC(__pkvm_host_unshare_hyp),
- HANDLE_FUNC(__pkvm_host_share_guest),
- HANDLE_FUNC(__pkvm_host_unshare_guest),
- HANDLE_FUNC(__pkvm_host_relax_perms_guest),
- HANDLE_FUNC(__pkvm_host_wrprotect_guest),
- HANDLE_FUNC(__pkvm_host_test_clear_young_guest),
- HANDLE_FUNC(__pkvm_host_mkyoung_guest),
HANDLE_FUNC(__kvm_adjust_pc),
HANDLE_FUNC(__kvm_vcpu_run),
HANDLE_FUNC(__kvm_flush_vm_context),
@@ -622,6 +585,15 @@ static const hcall_t host_hcall[] = {
HANDLE_FUNC(__kvm_timer_set_cntvoff),
HANDLE_FUNC(__vgic_v3_save_aprs),
HANDLE_FUNC(__vgic_v3_restore_vmcr_aprs),
+
+ HANDLE_FUNC(__pkvm_host_share_hyp),
+ HANDLE_FUNC(__pkvm_host_unshare_hyp),
+ HANDLE_FUNC(__pkvm_host_share_guest),
+ HANDLE_FUNC(__pkvm_host_unshare_guest),
+ HANDLE_FUNC(__pkvm_host_relax_perms_guest),
+ HANDLE_FUNC(__pkvm_host_wrprotect_guest),
+ HANDLE_FUNC(__pkvm_host_test_clear_young_guest),
+ HANDLE_FUNC(__pkvm_host_mkyoung_guest),
HANDLE_FUNC(__pkvm_reserve_vm),
HANDLE_FUNC(__pkvm_unreserve_vm),
HANDLE_FUNC(__pkvm_init_vm),
@@ -635,7 +607,7 @@ static const hcall_t host_hcall[] = {
static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
{
DECLARE_REG(unsigned long, id, host_ctxt, 0);
- unsigned long hcall_min = 0;
+ unsigned long hcall_min = 0, hcall_max = -1;
hcall_t hfn;

/*
@@ -647,14 +619,19 @@ static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
* basis. This is all fine, however, since __pkvm_prot_finalize
* returns -EPERM after the first call for a given CPU.
*/
- if (static_branch_unlikely(&kvm_protected_mode_initialized))
- hcall_min = __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize;
+ if (static_branch_unlikely(&kvm_protected_mode_initialized)) {
+ hcall_min = __KVM_HOST_SMCCC_FUNC_MIN_PKVM;
+ } else {
+ hcall_max = __KVM_HOST_SMCCC_FUNC_MAX_NO_PKVM;
+ }

id &= ~ARM_SMCCC_CALL_HINTS;
id -= KVM_HOST_SMCCC_ID(0);

- if (unlikely(id < hcall_min || id >= ARRAY_SIZE(host_hcall)))
+ if (unlikely(id < hcall_min || id > hcall_max ||
+ id >= ARRAY_SIZE(host_hcall))) {
goto inval;
+ }

hfn = host_hcall[id];
if (unlikely(!hfn))
--
2.53.0.473.g4a7958ca14-goog