[PATCH 13/65] target/arm: GICv5 cpuif: Initial skeleton and GSB barrier insns

[Peter Maydell <peter.maydell@linaro.org>]

In the GICv5 architecture, part of the GIC is implemented inside the
CPU: this is the CPU interface, which presents software with system
instructions and system registers, and communicates with the external
part of the GIC (the Interrupt Routing Service, IRS) via an
architected stream interface where both sides can send commands and
receive responses.

Add the initial source files for the GICv5 CPU interface, with
initial content implementing just the two GSB GIC barrier
instructions, which are no-ops for QEMU.

Since we will not initially implement virtualization or the "legacy
GICv3" interface that can be provided to a VM guest, we don't have
the ICH_VCTLR_EL2 register and do not need to implement an accessfn
for the "trap if at EL1 and EL2 enabled and legacy GICv3 is enabled"
handling.  We will come back and add this later as part of the
legacy-GICv3 code.

(The GICv3 has a similar architecture with part of the GIC being in
the CPU and part external; for QEMU we implemented the CPU interface
in hw/intc/, but in retrospect I think this was something of a design
mistake, and for GICv5 I am going to stick a bit closer to how the
hardware architecture splits things up; hence this code is in
target/arm.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/cpu-features.h    |  6 +++++
 target/arm/helper.c          |  1 +
 target/arm/internals.h       |  3 +++
 target/arm/tcg/gicv5-cpuif.c | 43 ++++++++++++++++++++++++++++++++++++
 target/arm/tcg/meson.build   |  1 +
 5 files changed, 54 insertions(+)
 create mode 100644 target/arm/tcg/gicv5-cpuif.c

diff --git a/target/arm/cpu-features.h b/target/arm/cpu-features.h
index b683c9551a..e391b394ba 100644
--- a/target/arm/cpu-features.h
+++ b/target/arm/cpu-features.h
@@ -280,6 +280,7 @@ FIELD(ID_AA64PFR1, PFAR, 60, 4)
 FIELD(ID_AA64PFR2, MTEPERM, 0, 4)
 FIELD(ID_AA64PFR2, MTESTOREONLY, 4, 4)
 FIELD(ID_AA64PFR2, MTEFAR, 8, 4)
+FIELD(ID_AA64PFR2, GCIE, 12, 4)
 FIELD(ID_AA64PFR2, FPMR, 32, 4)
 
 FIELD(ID_AA64MMFR0, PARANGE, 0, 4)
@@ -1159,6 +1160,11 @@ static inline bool isar_feature_aa64_gcs(const ARMISARegisters *id)
     return FIELD_EX64_IDREG(id, ID_AA64PFR1, GCS) != 0;
 }
 
+static inline bool isar_feature_aa64_gcie(const ARMISARegisters *id)
+{
+    return FIELD_EX64_IDREG(id, ID_AA64PFR2, GCIE) != 0;
+}
+
 static inline bool isar_feature_aa64_tgran4_lpa2(const ARMISARegisters *id)
 {
     return FIELD_SEX64_IDREG(id, ID_AA64MMFR0, TGRAN4) >= 1;
diff --git a/target/arm/helper.c b/target/arm/helper.c
index 6bfab90981..5e7cc039aa 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6315,6 +6315,7 @@ void register_cp_regs_for_features(ARMCPU *cpu)
     if (tcg_enabled()) {
         define_tlb_insn_regs(cpu);
         define_at_insn_regs(cpu);
+        define_gicv5_cpuif_regs(cpu);
     }
 #endif
 
diff --git a/target/arm/internals.h b/target/arm/internals.h
index 8ec2750847..9bde58cf00 100644
--- a/target/arm/internals.h
+++ b/target/arm/internals.h
@@ -1797,6 +1797,9 @@ void define_pm_cpregs(ARMCPU *cpu);
 /* Add the cpreg definitions for GCS cpregs */
 void define_gcs_cpregs(ARMCPU *cpu);
 
+/* Add the cpreg definitions for the GICv5 CPU interface */
+void define_gicv5_cpuif_regs(ARMCPU *cpu);
+
 /* Effective value of MDCR_EL2 */
 static inline uint64_t arm_mdcr_el2_eff(CPUARMState *env)
 {
diff --git a/target/arm/tcg/gicv5-cpuif.c b/target/arm/tcg/gicv5-cpuif.c
new file mode 100644
index 0000000000..76c2577c09
--- /dev/null
+++ b/target/arm/tcg/gicv5-cpuif.c
@@ -0,0 +1,43 @@
+/*
+ * GICv5 CPU interface
+ *
+ * Copyright (c) 2025 Linaro Limited
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "cpu.h"
+#include "internals.h"
+#include "cpregs.h"
+
+static const ARMCPRegInfo gicv5_cpuif_reginfo[] = {
+    /*
+     * Barrier: wait until the effects of a cpuif system register
+     * write have definitely made it to the IRS (and will thus show up
+     * in cpuif reads from the IRS by this or other CPUs and in the
+     * status of IRQ, FIQ etc). For QEMU we do all interaction with
+     * the IRS synchronously, so we can make this a nop.
+     */
+    {   .name = "GSB_SYS", .state = ARM_CP_STATE_AA64,
+        .opc0 = 1, .opc1 = 0, .crn = 12, .crm = 0, .opc2 = 0,
+        .access = PL1_W, .type = ARM_CP_NOP,
+    },
+    /*
+     * Barrier: wait until the effects of acknowledging an interrupt
+     * (via GICR CDIA or GICR CDNMIA) are visible, including the
+     * effect on the {IRQ,FIQ,vIRQ,vFIQ} pending state. This is
+     * a weaker version of GSB SYS. Again, for QEMU this is a nop.
+     */
+    {   .name = "GSB_ACK", .state = ARM_CP_STATE_AA64,
+        .opc0 = 1, .opc1 = 0, .crn = 12, .crm = 0, .opc2 = 1,
+        .access = PL1_W, .type = ARM_CP_NOP,
+    },
+};
+
+void define_gicv5_cpuif_regs(ARMCPU *cpu)
+{
+    if (cpu_isar_feature(aa64_gcie, cpu)) {
+        define_arm_cp_regs(cpu, gicv5_cpuif_reginfo);
+    }
+}
diff --git a/target/arm/tcg/meson.build b/target/arm/tcg/meson.build
index 5f59156055..a67911f8dc 100644
--- a/target/arm/tcg/meson.build
+++ b/target/arm/tcg/meson.build
@@ -62,6 +62,7 @@ arm_common_ss.add(files(
 arm_common_system_ss.add(files(
   'cpregs-at.c',
   'debug.c',
+  'gicv5-cpuif.c',
   'hflags.c',
   'neon_helper.c',
   'psci.c',
-- 
2.43.0