KVM: arm64: Writable TGRAN*_2

Commit Message

Sebastian Ott March 6, 2025, 6:40 p.m. UTC

Allow userspace to write the safe (NI) value for ID_AA64MMFR0_EL1.TGRAN*_2.
Disallow to change these fields for NV since kvm provides a sanitized view
for them based on the PAGE_SIZE.
Also add these bits to the set_id_regs selftest.

Signed-off-by: Sebastian Ott <[e-mail]>
---
 arch/arm64/kvm/sys_regs.c                     | 21 +++++++++++++++----
 .../testing/selftests/kvm/arm64/set_id_regs.c |  3 +++
 2 files changed, 20 insertions(+), 4 deletions(-)

Patch

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 14faf213d483..0730ed8314d0 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1948,6 +1948,21 @@  static int set_id_aa64pfr1_el1(struct kvm_vcpu *vcpu,
 	return set_id_reg(vcpu, rd, user_val);
 }
 
+static int set_id_aa64mmfr0_el1(struct kvm_vcpu *vcpu,
+				const struct sys_reg_desc *rd, u64 user_val)
+{
+	u64 sanitized_val = kvm_read_sanitised_id_reg(vcpu, rd);
+	u64 tgran2_mask = ID_AA64MMFR0_EL1_TGRAN4_2_MASK |
+			  ID_AA64MMFR0_EL1_TGRAN16_2_MASK |
+			  ID_AA64MMFR0_EL1_TGRAN64_2_MASK;
+
+	if (vcpu_has_nv(vcpu) &&
+	    ((sanitized_val & tgran2_mask) != (user_val & tgran2_mask)))
+		return -EINVAL;
+
+	return set_id_reg(vcpu, rd, user_val);
+}
+
 static int set_id_aa64mmfr2_el1(struct kvm_vcpu *vcpu,
 				const struct sys_reg_desc *rd, u64 user_val)
 {
@@ -2787,10 +2802,8 @@  static const struct sys_reg_desc sys_reg_descs[] = {
 	ID_UNALLOCATED(6,7),
 
 	/* CRm=7 */
-	ID_WRITABLE(ID_AA64MMFR0_EL1, ~(ID_AA64MMFR0_EL1_RES0 |
-					ID_AA64MMFR0_EL1_TGRAN4_2 |
-					ID_AA64MMFR0_EL1_TGRAN64_2 |
-					ID_AA64MMFR0_EL1_TGRAN16_2 |
+	ID_FILTERED(ID_AA64MMFR0_EL1, id_aa64mmfr0_el1,
+				      ~(ID_AA64MMFR0_EL1_RES0 |
 					ID_AA64MMFR0_EL1_ASIDBITS)),
 	ID_WRITABLE(ID_AA64MMFR1_EL1, ~(ID_AA64MMFR1_EL1_RES0 |
 					ID_AA64MMFR1_EL1_HCX |
diff --git a/tools/testing/selftests/kvm/arm64/set_id_regs.c b/tools/testing/selftests/kvm/arm64/set_id_regs.c
index 1d65f4a09e6f..322b9d3b0125 100644
--- a/tools/testing/selftests/kvm/arm64/set_id_regs.c
+++ b/tools/testing/selftests/kvm/arm64/set_id_regs.c
@@ -146,6 +146,9 @@  static const struct reg_ftr_bits ftr_id_aa64pfr1_el1[] = {
 static const struct reg_ftr_bits ftr_id_aa64mmfr0_el1[] = {
 	REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64MMFR0_EL1, ECV, 0),
 	REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64MMFR0_EL1, EXS, 0),
+	REG_FTR_BITS(FTR_EXACT, ID_AA64MMFR0_EL1, TGRAN4_2, 1),
+	REG_FTR_BITS(FTR_EXACT, ID_AA64MMFR0_EL1, TGRAN64_2, 1),
+	REG_FTR_BITS(FTR_EXACT, ID_AA64MMFR0_EL1, TGRAN16_2, 1),
 	S_REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64MMFR0_EL1, TGRAN4, 0),
 	S_REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64MMFR0_EL1, TGRAN64, 0),
 	REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64MMFR0_EL1, TGRAN16, 0),