Merge branch kvm-arm64/nv-misc-6.18 into kvmarm-master/next

* kvm-arm64/nv-misc-6.18:
  : .
  : Various NV-related fixes:
  :
  : - Relax KVM's SError injection to consider that HCR_EL2.AMO's
  :   effective value is 1 when HCR_EL2.{E2H,TGE)=={1,0}.
  :   (20250918164632.410404-1-oliver.upton@linux.dev)
  :
  : - Allow userspace to disable some S2 base granule sizes
  :   (20250918165505.415017-1-oliver.upton@linux.dev)
  : .
  KVM: arm64: nv: Allow userspace to de-feature stage-2 TGRANs
  KVM: arm64: nv: Treat AMO as 1 when at EL2 and {E2H,TGE} = {1, 0}

Signed-off-by: Marc Zyngier <maz@kernel.org>

2 files changed, 32 insertions, 5 deletions

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index fa8a08a1ccd5..64ce3fec73ee 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -220,6 +220,20 @@ static inline bool vcpu_el2_tge_is_set(const struct kvm_vcpu *vcpu)
 
 static inline bool vcpu_el2_amo_is_set(const struct kvm_vcpu *vcpu)
 {
+	/*
+	 * DDI0487L.b Known Issue D22105
+	 *
+	 * When executing at EL2 and HCR_EL2.{E2H,TGE} = {1, 0} it is
+	 * IMPLEMENTATION DEFINED whether the effective value of HCR_EL2.AMO
+	 * is the value programmed or 1.
+	 *
+	 * Make the implementation choice of treating the effective value as 1 as
+	 * we cannot subsequently catch changes to TGE or AMO that would
+	 * otherwise lead to the SError becoming deliverable.
+	 */
+	if (vcpu_is_el2(vcpu) && vcpu_el2_e2h_is_set(vcpu) && !vcpu_el2_tge_is_set(vcpu))
+		return true;
+
 	return ctxt_sys_reg(&vcpu->arch.ctxt, HCR_EL2) & HCR_AMO;
 }
 
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index caf80c324b35..4bb877e4280f 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -2173,16 +2173,29 @@ static int set_id_aa64pfr1_el1(struct kvm_vcpu *vcpu,
 	return set_id_reg(vcpu, rd, user_val);
 }
 
+/*
+ * Allow userspace to de-feature a stage-2 translation granule but prevent it
+ * from claiming the impossible.
+ */
+#define tgran2_val_allowed(tg, safe, user)			\
+({								\
+	u8 __s = SYS_FIELD_GET(ID_AA64MMFR0_EL1, tg, safe);	\
+	u8 __u = SYS_FIELD_GET(ID_AA64MMFR0_EL1, tg, user);	\
+								\
+	__s == __u || __u == ID_AA64MMFR0_EL1_##tg##_NI;	\
+})
+
 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)))
+	if (!vcpu_has_nv(vcpu))
+		return set_id_reg(vcpu, rd, user_val);
+
+	if (!tgran2_val_allowed(TGRAN4_2, sanitized_val, user_val) ||
+	    !tgran2_val_allowed(TGRAN16_2, sanitized_val, user_val) ||
+	    !tgran2_val_allowed(TGRAN64_2, sanitized_val, user_val))
 		return -EINVAL;
 
 	return set_id_reg(vcpu, rd, user_val);