xen/arm: Add handler for cp15 ID registers

Add support for emulation of cp15 based ID registers (on arm32 or when
running a 32bit guest on arm64).
The handlers are returning the values stored in the guest_cpuinfo
structure for known registers and RAZ for all reserved registers.
In the current status the MVFR registers are no supported.

Signed-off-by: Bertrand Marquis <bertrand.marquis@arm.com>
[Stefano: fix code style]
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/vcpreg.c

@@ -155,6 +155,24 @@ TVM_REG32(CONTEXTIDR, CONTEXTIDR_EL1)
         break;                                                      \
     }
 
+/* Macro to generate easily case for ID co-processor emulation */
+#define GENERATE_TID3_INFO(reg, field, offset)                      \
+    case HSR_CPREG32(reg):                                          \
+    {                                                               \
+        return handle_ro_read_val(regs, regidx, cp32.read, hsr, 1,  \
+                                  guest_cpuinfo.field.bits[offset]);\
+    }
+
+/* helper to define cases for all registers for one CRm value */
+#define HSR_CPREG32_TID3_CASES(REG)     case HSR_CPREG32(p15,0,c0,REG,0): \
+                                        case HSR_CPREG32(p15,0,c0,REG,1): \
+                                        case HSR_CPREG32(p15,0,c0,REG,2): \
+                                        case HSR_CPREG32(p15,0,c0,REG,3): \
+                                        case HSR_CPREG32(p15,0,c0,REG,4): \
+                                        case HSR_CPREG32(p15,0,c0,REG,5): \
+                                        case HSR_CPREG32(p15,0,c0,REG,6): \
+                                        case HSR_CPREG32(p15,0,c0,REG,7)
+
 void do_cp15_32(struct cpu_user_regs *regs, const union hsr hsr)
 {
     const struct hsr_cp32 cp32 = hsr.cp32;
@@ -286,6 +304,53 @@ void do_cp15_32(struct cpu_user_regs *regs, const union hsr hsr)
          */
         return handle_raz_wi(regs, regidx, cp32.read, hsr, 1);
 
+    /*
+     * HCR_EL2.TID3
+     *
+     * This is trapping most Identification registers used by a guest
+     * to identify the processor features
+     */
+    GENERATE_TID3_INFO(ID_PFR0, pfr32, 0)
+    GENERATE_TID3_INFO(ID_PFR1, pfr32, 1)
+    GENERATE_TID3_INFO(ID_PFR2, pfr32, 2)
+    GENERATE_TID3_INFO(ID_DFR0, dbg32, 0)
+    GENERATE_TID3_INFO(ID_DFR1, dbg32, 1)
+    GENERATE_TID3_INFO(ID_AFR0, aux32, 0)
+    GENERATE_TID3_INFO(ID_MMFR0, mm32, 0)
+    GENERATE_TID3_INFO(ID_MMFR1, mm32, 1)
+    GENERATE_TID3_INFO(ID_MMFR2, mm32, 2)
+    GENERATE_TID3_INFO(ID_MMFR3, mm32, 3)
+    GENERATE_TID3_INFO(ID_MMFR4, mm32, 4)
+    GENERATE_TID3_INFO(ID_MMFR5, mm32, 5)
+    GENERATE_TID3_INFO(ID_ISAR0, isa32, 0)
+    GENERATE_TID3_INFO(ID_ISAR1, isa32, 1)
+    GENERATE_TID3_INFO(ID_ISAR2, isa32, 2)
+    GENERATE_TID3_INFO(ID_ISAR3, isa32, 3)
+    GENERATE_TID3_INFO(ID_ISAR4, isa32, 4)
+    GENERATE_TID3_INFO(ID_ISAR5, isa32, 5)
+    GENERATE_TID3_INFO(ID_ISAR6, isa32, 6)
+    /* MVFR registers are in cp10 not cp15 */
+
+    /*
+     * Those cases are catching all Reserved registers trapped by TID3 which
+     * currently have no assignment.
+     * HCR.TID3 is trapping all registers in the group 3:
+     * coproc == p15, opc1 == 0, CRn == c0, CRm == {c2-c7}, opc2 == {0-7}.
+     * Those registers are defined as being RO in the Arm Architecture
+     * Reference manual Armv8 (Chapter D12.3.2 of issue F.c) so handle them
+     * as Read-only read as zero.
+     */
+    case HSR_CPREG32(p15,0,c0,c3,0):
+    case HSR_CPREG32(p15,0,c0,c3,1):
+    case HSR_CPREG32(p15,0,c0,c3,2):
+    case HSR_CPREG32(p15,0,c0,c3,3):
+    case HSR_CPREG32(p15,0,c0,c3,7):
+    HSR_CPREG32_TID3_CASES(c4):
+    HSR_CPREG32_TID3_CASES(c5):
+    HSR_CPREG32_TID3_CASES(c6):
+    HSR_CPREG32_TID3_CASES(c7):
+        return handle_ro_raz(regs, regidx, cp32.read, hsr, 1);
+
     /*
      * HCR_EL2.TIDCP
      *