arm64/cpufeature: Introduce ID_DFR1 CPU register

This adds basic building blocks required for ID_DFR1 CPU register which
provides top level information about the debug system in AArch32 state.
We hide the register from KVM guests, as we don't emulate the 'MTPMU'
feature.

This is added per ARM DDI 0487F.a specification.

Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: James Morse <[email protected]>
Cc: Suzuki K Poulose <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]

Suggested-by: Will Deacon <[email protected]>
Reviewed-by : Suzuki K Poulose <[email protected]>
Signed-off-by: Anshuman Khandual <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

Author: Anshuman Khandual

arch/arm64/include/asm/cpu.h

@@ -33,6 +33,7 @@ struct cpuinfo_arm64 {
 	u64		reg_id_aa64zfr0;
 
 	u32		reg_id_dfr0;
+	u32		reg_id_dfr1;
 	u32		reg_id_isar0;
 	u32		reg_id_isar1;
 	u32		reg_id_isar2;

arch/arm64/include/asm/sysreg.h

@@ -140,6 +140,7 @@
 #define SYS_ID_PFR1_EL1			sys_reg(3, 0, 0, 1, 1)
 #define SYS_ID_PFR2_EL1			sys_reg(3, 0, 0, 3, 4)
 #define SYS_ID_DFR0_EL1			sys_reg(3, 0, 0, 1, 2)
+#define SYS_ID_DFR1_EL1			sys_reg(3, 0, 0, 3, 5)
 #define SYS_ID_AFR0_EL1			sys_reg(3, 0, 0, 1, 3)
 #define SYS_ID_MMFR0_EL1		sys_reg(3, 0, 0, 1, 4)
 #define SYS_ID_MMFR1_EL1		sys_reg(3, 0, 0, 1, 5)
@@ -767,6 +768,8 @@
 #define ID_ISAR4_WITHSHIFTS_SHIFT	4
 #define ID_ISAR4_UNPRIV_SHIFT		0
 
+#define ID_DFR1_MTPMU_SHIFT		0
+
 #define ID_ISAR0_DIVIDE_SHIFT		24
 #define ID_ISAR0_DEBUG_SHIFT		20
 #define ID_ISAR0_COPROC_SHIFT		16

arch/arm64/kernel/cpufeature.c

@@ -457,6 +457,11 @@ static const struct arm64_ftr_bits ftr_id_dfr0[] = {
 	ARM64_FTR_END,
 };
 
+static const struct arm64_ftr_bits ftr_id_dfr1[] = {
+	S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_DFR1_MTPMU_SHIFT, 4, 0),
+	ARM64_FTR_END,
+};
+
 static const struct arm64_ftr_bits ftr_zcr[] = {
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE,
 		ZCR_ELx_LEN_SHIFT, ZCR_ELx_LEN_SIZE, 0),	/* LEN */
@@ -527,6 +532,7 @@ static const struct __ftr_reg_entry {
 	ARM64_FTR_REG(SYS_MVFR1_EL1, ftr_generic_32bits),
 	ARM64_FTR_REG(SYS_MVFR2_EL1, ftr_mvfr2),
 	ARM64_FTR_REG(SYS_ID_PFR2_EL1, ftr_id_pfr2),
+	ARM64_FTR_REG(SYS_ID_DFR1_EL1, ftr_id_dfr1),
 
 	/* Op1 = 0, CRn = 0, CRm = 4 */
 	ARM64_FTR_REG(SYS_ID_AA64PFR0_EL1, ftr_id_aa64pfr0),
@@ -720,6 +726,7 @@ void __init init_cpu_features(struct cpuinfo_arm64 *info)
 
 	if (id_aa64pfr0_32bit_el0(info->reg_id_aa64pfr0)) {
 		init_cpu_ftr_reg(SYS_ID_DFR0_EL1, info->reg_id_dfr0);
+		init_cpu_ftr_reg(SYS_ID_DFR1_EL1, info->reg_id_dfr1);
 		init_cpu_ftr_reg(SYS_ID_ISAR0_EL1, info->reg_id_isar0);
 		init_cpu_ftr_reg(SYS_ID_ISAR1_EL1, info->reg_id_isar1);
 		init_cpu_ftr_reg(SYS_ID_ISAR2_EL1, info->reg_id_isar2);
@@ -835,6 +842,8 @@ static int update_32bit_cpu_features(int cpu, struct cpuinfo_arm64 *info,
 
 	taint |= check_update_ftr_reg(SYS_ID_DFR0_EL1, cpu,
 				      info->reg_id_dfr0, boot->reg_id_dfr0);
+	taint |= check_update_ftr_reg(SYS_ID_DFR1_EL1, cpu,
+				      info->reg_id_dfr1, boot->reg_id_dfr1);
 	taint |= check_update_ftr_reg(SYS_ID_ISAR0_EL1, cpu,
 				      info->reg_id_isar0, boot->reg_id_isar0);
 	taint |= check_update_ftr_reg(SYS_ID_ISAR1_EL1, cpu,
@@ -998,6 +1007,7 @@ static u64 __read_sysreg_by_encoding(u32 sys_id)
 	read_sysreg_case(SYS_ID_PFR1_EL1);
 	read_sysreg_case(SYS_ID_PFR2_EL1);
 	read_sysreg_case(SYS_ID_DFR0_EL1);
+	read_sysreg_case(SYS_ID_DFR1_EL1);
 	read_sysreg_case(SYS_ID_MMFR0_EL1);
 	read_sysreg_case(SYS_ID_MMFR1_EL1);
 	read_sysreg_case(SYS_ID_MMFR2_EL1);

arch/arm64/kernel/cpuinfo.c

@@ -362,6 +362,7 @@ static void __cpuinfo_store_cpu(struct cpuinfo_arm64 *info)
 	/* Update the 32bit ID registers only if AArch32 is implemented */
 	if (id_aa64pfr0_32bit_el0(info->reg_id_aa64pfr0)) {
 		info->reg_id_dfr0 = read_cpuid(ID_DFR0_EL1);
+		info->reg_id_dfr1 = read_cpuid(ID_DFR1_EL1);
 		info->reg_id_isar0 = read_cpuid(ID_ISAR0_EL1);
 		info->reg_id_isar1 = read_cpuid(ID_ISAR1_EL1);
 		info->reg_id_isar2 = read_cpuid(ID_ISAR2_EL1);

arch/arm64/kvm/sys_regs.c

@@ -1457,7 +1457,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	ID_SANITISED(MVFR2_EL1),
 	ID_UNALLOCATED(3,3),
 	ID_SANITISED(ID_PFR2_EL1),
-	ID_UNALLOCATED(3,5),
+	ID_HIDDEN(ID_DFR1_EL1),
 	ID_UNALLOCATED(3,6),
 	ID_UNALLOCATED(3,7),