[PATCH 08/16] KVM: arm64: Advertise TCR2, SCTLR2, S1PIE and S1POE to protected VMs

From: Fuad Tabba

Date: Mon Nov 09 2026 - 03:39:15 EST


Advertise FEAT_TCR2, FEAT_SCTLR2, FEAT_S1PIE and FEAT_S1POE to
protected VMs, with S1POE only when the kernel supports POE, as EL2
doesn't switch the POE registers otherwise. With the fields set,
vcpu_set_hcrx() sets HCRX_EL2.{TCR2En,SCTLR2En} for them, and since
the previous patch their PIE and POE registers don't trap.

Reset the new registers as KVM does for a non-protected vCPU.

Signed-off-by: Fuad Tabba <fuad.tabba@xxxxxxxxx>
---
arch/arm64/include/asm/kvm_hyp.h | 1 +
arch/arm64/kvm/arm.c | 1 +
arch/arm64/kvm/hyp/nvhe/sys_regs.c | 24 +++++++++++++++++++++++-
3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
index 920c1d8d45b1a..ab22b395d0908 100644
--- a/arch/arm64/include/asm/kvm_hyp.h
+++ b/arch/arm64/include/asm/kvm_hyp.h
@@ -151,6 +151,7 @@ extern u64 kvm_nvhe_sym(id_aa64isar2_el1_sys_val);
extern u64 kvm_nvhe_sym(id_aa64mmfr0_el1_sys_val);
extern u64 kvm_nvhe_sym(id_aa64mmfr1_el1_sys_val);
extern u64 kvm_nvhe_sym(id_aa64mmfr2_el1_sys_val);
+extern u64 kvm_nvhe_sym(id_aa64mmfr3_el1_sys_val);
extern u64 kvm_nvhe_sym(id_aa64smfr0_el1_sys_val);
extern u64 kvm_nvhe_sym(id_aa64dfr0_el1_sys_val);

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 2753686982f0b..fe60535e4f358 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -2834,6 +2834,7 @@ static void kvm_hyp_init_symbols(void)
kvm_nvhe_sym(id_aa64mmfr0_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
kvm_nvhe_sym(id_aa64mmfr1_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
kvm_nvhe_sym(id_aa64mmfr2_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64MMFR2_EL1);
+ kvm_nvhe_sym(id_aa64mmfr3_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64MMFR3_EL1);
kvm_nvhe_sym(id_aa64smfr0_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64SMFR0_EL1);
kvm_nvhe_sym(id_aa64dfr0_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1);
kvm_nvhe_sym(__icache_flags) = __icache_flags;
diff --git a/arch/arm64/kvm/hyp/nvhe/sys_regs.c b/arch/arm64/kvm/hyp/nvhe/sys_regs.c
index 78c25da737591..d186aba6aa09c 100644
--- a/arch/arm64/kvm/hyp/nvhe/sys_regs.c
+++ b/arch/arm64/kvm/hyp/nvhe/sys_regs.c
@@ -30,6 +30,7 @@ u64 id_aa64isar2_el1_sys_val;
u64 id_aa64mmfr0_el1_sys_val;
u64 id_aa64mmfr1_el1_sys_val;
u64 id_aa64mmfr2_el1_sys_val;
+u64 id_aa64mmfr3_el1_sys_val;
u64 id_aa64smfr0_el1_sys_val;
u64 id_aa64dfr0_el1_sys_val;

@@ -83,6 +84,11 @@ static bool vm_has_sve(const struct kvm *kvm)
return system_supports_sve() && kvm_vcpu_has_feature(kvm, KVM_ARM_VCPU_SVE);
}

+static bool vm_has_s1poe(const struct kvm *kvm)
+{
+ return system_supports_poe();
+}
+
/*
* Definitions for features to be allowed or restricted for protected guests.
*
@@ -177,6 +183,14 @@ static const struct pvm_ftr_bits pvmid_aa64mmfr2[] = {
FEAT_END
};

+static const struct pvm_ftr_bits pvmid_aa64mmfr3[] = {
+ MAX_FEAT(ID_AA64MMFR3_EL1, TCRX, IMP),
+ MAX_FEAT(ID_AA64MMFR3_EL1, SCTLRX, IMP),
+ MAX_FEAT(ID_AA64MMFR3_EL1, S1PIE, IMP),
+ MAX_FEAT_FUNC(ID_AA64MMFR3_EL1, S1POE, IMP, vm_has_s1poe),
+ FEAT_END
+};
+
static const struct pvm_ftr_bits pvmid_aa64isar1[] = {
MAX_FEAT(ID_AA64ISAR1_EL1, DPB, DPB2),
MAX_FEAT_FUNC(ID_AA64ISAR1_EL1, APA, PAuth, vm_has_ptrauth),
@@ -274,6 +288,8 @@ static u64 pvm_calc_id_reg(const struct kvm_vcpu *vcpu, u32 id)
return get_restricted_features(vcpu, id_aa64mmfr1_el1_sys_val, pvmid_aa64mmfr1);
case SYS_ID_AA64MMFR2_EL1:
return get_restricted_features(vcpu, id_aa64mmfr2_el1_sys_val, pvmid_aa64mmfr2);
+ case SYS_ID_AA64MMFR3_EL1:
+ return get_restricted_features(vcpu, id_aa64mmfr3_el1_sys_val, pvmid_aa64mmfr3);
case SYS_ID_AA64DFR0_EL1:
return get_restricted_features(vcpu, id_aa64dfr0_el1_sys_val, pvmid_aa64dfr0);
case SYS_ID_AA64MMFR4_EL1:
@@ -707,7 +723,7 @@ static const struct sys_reg_desc pvm_sys_reg_descs[] = {
AARCH64(SYS_ID_AA64MMFR0_EL1),
AARCH64(SYS_ID_AA64MMFR1_EL1),
AARCH64(SYS_ID_AA64MMFR2_EL1),
- ID_UNALLOCATED(7,3),
+ AARCH64(SYS_ID_AA64MMFR3_EL1),
ID_UNALLOCATED(7,4),
ID_UNALLOCATED(7,5),
ID_UNALLOCATED(7,6),
@@ -793,7 +809,13 @@ static const struct sys_reg_desc_reset pvm_sys_reg_reset_vals[] = {
RESET_ZERO(CPACR_EL1),
RESET_VAL(CONTEXTIDR_EL1, 0x00000000dbadc0deULL),
RESET_VAL(SCTLR_EL1, 0x00C50078ULL),
+ RESET_ZERO(SCTLR2_EL1),
RESET_ZERO(TCR_EL1),
+ RESET_ZERO(TCR2_EL1),
+ RESET_UNKNOWN(PIR_EL1),
+ RESET_UNKNOWN(PIRE0_EL1),
+ RESET_UNKNOWN(POR_EL1),
+ RESET_UNKNOWN(POR_EL0),
RESET_UNKNOWN(AFSR0_EL1),
RESET_UNKNOWN(AFSR1_EL1),
RESET_UNKNOWN(ESR_EL1),
--
2.47.3