target/riscv: add profile->present flag

Björn reported in [1] a case where a rv64 CPU is going through the
profile code path to enable satp mode. In this case,the amount of
extensions on top of the rv64 CPU made it compliant with the RVA22S64
profile during the validation of CPU 0. When the subsequent CPUs were
initialized the static profile object has the 'enable' flag set,
enabling the profile code path for those CPUs.

This happens because we are initializing and realizing each CPU before
going to the next, i.e. init and realize CPU0, then init and realize
CPU1 and so on. If we change any persistent state during the validation
of CPU N it will interfere with the init/realization of CPU N+1.

We're using the 'enabled' profile flag to do two distinct things: inform
cpu_init() that we want profile extensions to be enabled, and telling
QMP that a profile is currently enabled in the CPU. We want to be
flexible enough to recognize profile support for all CPUs that has the
extension prerequisites, but we do not want to force the profile code
path if a profile wasn't set too.

Add a new 'present' flag for profiles that will coexist with the 'enabled'
flag. Enabling a profile means "we want to switch on all its mandatory
extensions". A profile is 'present' if we asserted during validation
that the CPU has the needed prerequisites.

This means that the case reported by Björn now results in
RVA22S64.enabled=false and RVA22S64.present=true. QMP will recognize it
as a RVA22 compliant CPU and we won't force the CPU into the profile
path.

[1] https://lore.kernel.org/qemu-riscv/87y0usiz22.fsf@all.your.base.are.belong.to.us/

Reported-by: Björn Töpel <bjorn@kernel.org>
Fixes: 2af005d610 ("target/riscv/tcg: validate profiles during finalize")
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Message-ID: <20250528184407.1451983-4-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 229ade9ed918ded88471d2f504f7edec24badf6f..2a6793e0225d4f97d06f3c81a00b59aea6c7b1df 100644 (file)
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -82,7 +82,22 @@ typedef struct riscv_cpu_profile {
     struct riscv_cpu_profile *s_parent;
     const char *name;
     uint32_t misa_ext;
+    /*
+     * The profile is enabled/disabled via command line or
+     * via cpu_init(). Enabling a profile will add all its
+     * mandatory extensions in the CPU during init().
+     */
     bool enabled;
+    /*
+     * The profile is present in the CPU, i.e. the current set of
+     * CPU extensions complies with it. A profile can be enabled
+     * and not present (e.g. the user disabled a mandatory extension)
+     * and the other way around (e.g. all mandatory extensions are
+     * present in a non-profile CPU).
+     *
+     * QMP uses this flag.
+     */
+    bool present;
     bool user_set;
     int priv_spec;
     int satp_mode;

diff --git a/target/riscv/riscv-qmp-cmds.c b/target/riscv/riscv-qmp-cmds.c
index 8ba8aa0d5f86b0f6054f3f88e93191fbf3c52709..8a1856c50e0f6c889b7bb402fa6b87e7b79c1b86 100644 (file)
--- a/target/riscv/riscv-qmp-cmds.c
+++ b/target/riscv/riscv-qmp-cmds.c
@@ -121,7 +121,7 @@ static void riscv_obj_add_profiles_qdict(Object *obj, QDict *qdict_out)
 
     for (int i = 0; riscv_profiles[i] != NULL; i++) {
         profile = riscv_profiles[i];
-        value = QOBJECT(qbool_from_bool(profile->enabled));
+        value = QOBJECT(qbool_from_bool(profile->present));
 
         qdict_put_obj(qdict_out, profile->name, value);
     }

diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
index e10e03a577ffa96c2bdf60d13fee1992037a56a6..c5e260e360eec6d31699c2bc460313cc34b27af1 100644 (file)
--- a/target/riscv/tcg/tcg-cpu.c
+++ b/target/riscv/tcg/tcg-cpu.c
@@ -867,16 +867,11 @@ static void riscv_cpu_check_parent_profile(RISCVCPU *cpu,
                                            RISCVCPUProfile *profile,
                                            RISCVCPUProfile *parent)
 {
-    const char *parent_name;
-    bool parent_enabled;
-
-    if (!profile->enabled || !parent) {
+    if (!profile->present || !parent) {
         return;
     }
 
-    parent_name = parent->name;
-    parent_enabled = object_property_get_bool(OBJECT(cpu), parent_name, NULL);
-    profile->enabled = parent_enabled;
+    profile->present = parent->present;
 }
 
 static void riscv_cpu_validate_profile(RISCVCPU *cpu,
@@ -937,7 +932,7 @@ static void riscv_cpu_validate_profile(RISCVCPU *cpu,
         }
     }
 
-    profile->enabled = profile_impl;
+    profile->present = profile_impl;
 
     riscv_cpu_check_parent_profile(cpu, profile, profile->u_parent);
     riscv_cpu_check_parent_profile(cpu, profile, profile->s_parent);