RE: [PATCH v4 1/3] target-arm: Add support for Fujitsu A64FX

["ishii.shuuichir@fujitsu.com" <ishii.shuuichir@fujitsu.com>]

> On Thu, 12 Aug 2021 at 10:25, Andrew Jones <drjones@redhat.com> wrote:
> > On second thought, do we want the QMP CPU model expansion query to
> > show that this CPU type has sve,sve128,sve256,sve512? If so, then our
> > SVE work isn't complete, because we need those properties, set true by
> > default, but forbidden from changing.
> 
> Do we have precedent elsewhere (arm, x86, wherever) for "this CPU object
> exposes these properties as constant unwriteable" ?

We have not yet conducted a confirmation of Peter's question, but...

> On second thought, do we want the QMP CPU model expansion query to show that
> this CPU type has sve,sve128,sve256,sve512? If so, then our SVE work isn't
> complete, because we need those properties, set true by default, but forbidden
> from changing.

Based on Andrew's comment, 
We have created a patch based on v4 that works as intended in QMP.

----------
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 162e46afc3..2d9f779cb6 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -1345,29 +1345,12 @@ static void arm_cpu_finalizefn(Object *obj)
 #endif
 }

-static void a64fx_cpu_set_sve(ARMCPU *cpu)
-{
-    /* Suppport of A64FX's vector length are 128,256 and 512bit only */
-    bitmap_zero(cpu->sve_vq_map, ARM_MAX_VQ);
-    bitmap_zero(cpu->sve_vq_init, ARM_MAX_VQ);
-    set_bit(0, cpu->sve_vq_map); /* 128bit */
-    set_bit(0, cpu->sve_vq_init);
-    set_bit(1, cpu->sve_vq_map); /* 256bit */
-    set_bit(1, cpu->sve_vq_init);
-    set_bit(3, cpu->sve_vq_map); /* 512bit */
-    set_bit(3, cpu->sve_vq_init);
-
-    cpu->sve_max_vq = find_last_bit(cpu->sve_vq_map, ARM_MAX_VQ) + 1;
-}
-
 void arm_cpu_finalize_features(ARMCPU *cpu, Error **errp)
 {
     Error *local_err = NULL;

     if (arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
-        if (arm_feature(&cpu->env, ARM_FEATURE_A64FX)) {
-            a64fx_cpu_set_sve(cpu);
-        } else {
+        if (!arm_feature(&cpu->env, ARM_FEATURE_A64FX)) {
             arm_cpu_sve_finalize(cpu, &local_err);
             if (local_err != NULL) {
                 error_propagate(errp, local_err);
diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c
index 5e7e885f9d..1ec2a7c6da 100644
--- a/target/arm/cpu64.c
+++ b/target/arm/cpu64.c
@@ -847,6 +847,23 @@ static void aarch64_max_initfn(Object *obj)
                         cpu_max_set_sve_max_vq, NULL, NULL);
 }

+static void a64fx_cpu_set_sve(Object *obj)
+{
+    int i;
+    Error *errp = NULL;
+    ARMCPU *cpu = ARM_CPU(obj);
+    /* Suppport of A64FX's vector length are 128,256 and 512bit only */
+    const char *vl[] = {"sve128", "sve256", "sve512"};
+
+    for(i = 0; i <sizeof(vl)/sizeof(vl[0]); i++){
+        object_property_add(obj, vl[i], "bool", cpu_arm_get_sve_vq,
+                            cpu_arm_set_sve_vq, NULL, NULL);
+        object_property_set_bool(obj, vl[i], true, &errp);
+    }
+
+    cpu->sve_max_vq = find_last_bit(cpu->sve_vq_map, ARM_MAX_VQ) + 1;
+}
+
 static void aarch64_a64fx_initfn(Object *obj)
 {
     ARMCPU *cpu = ARM_CPU(obj);
@@ -885,6 +902,9 @@ static void aarch64_a64fx_initfn(Object *obj)
     cpu->gic_vpribits = 5;
     cpu->gic_vprebits = 5;

+    /* Set SVE properties */
+    a64fx_cpu_set_sve(obj);
+
     /* TODO:  Add A64FX specific HPC extension registers */
 }
----------

In the case of the patch above,
it is possible to identify only the SVE vector length supported by A64FX from QMP, 
as shown in the following result.

----------
Welcome to the QMP low-level shell!
Connected to QEMU 6.0.93

(QEMU) query-cpu-model-expansion type=full model={"name":"a64fx"}
{"return": {"model": {"name": "a64fx", "props": {"sve128": true, "sve256": true, "sve512": true, "aarch64": true, "pmu": true}}}}
(QEMU)
----------

How about this kind of fix?
However, by allowing the sve128, sve256, and sve512 properties to be specified, 
the user can explicitly change the settings (ex: sve128=off), 
but the only properties that can be set is the vector length supported by A64FX. 
We personally think this is a no problem.

We would appreciate your comments.

Best regards.

> -----Original Message-----
> From: Andrew Jones <drjones@redhat.com>
> Sent: Thursday, August 12, 2021 6:25 PM
> To: Ishii, Shuuichirou/石井 周一郎 <ishii.shuuichir@fujitsu.com>
> Cc: peter.maydell@linaro.org; qemu-arm@nongnu.org; qemu-devel@nongnu.org
> Subject: Re: [PATCH v4 1/3] target-arm: Add support for Fujitsu A64FX
> 
> On Thu, Aug 12, 2021 at 11:16:50AM +0200, Andrew Jones wrote:
> > On Thu, Aug 12, 2021 at 03:04:38PM +0900, Shuuichirou Ishii wrote:
> > > Add a definition for the Fujitsu A64FX processor.
> > >
> > > The A64FX processor does not implement the AArch32 Execution state,
> > > so there are no associated AArch32 Identification registers.
> > >
> > > For SVE, the A64FX processor supports only 128,256 and 512bit vector
> lengths.
> > >
> > > Signed-off-by: Shuuichirou Ishii <ishii.shuuichir@fujitsu.com>
> > > ---
> > >  target/arm/cpu.c   | 27 +++++++++++++++++++++++----
> > >  target/arm/cpu.h   |  1 +
> > >  target/arm/cpu64.c | 42
> ++++++++++++++++++++++++++++++++++++++++++
> > >  3 files changed, 66 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/target/arm/cpu.c b/target/arm/cpu.c index
> > > 2866dd7658..162e46afc3 100644
> > > --- a/target/arm/cpu.c
> > > +++ b/target/arm/cpu.c
> > > @@ -1345,15 +1345,34 @@ static void arm_cpu_finalizefn(Object *obj)
> > > #endif  }
> > >
> > > +static void a64fx_cpu_set_sve(ARMCPU *cpu) {
> > > +    /* Suppport of A64FX's vector length are 128,256 and 512bit only */
> > > +    bitmap_zero(cpu->sve_vq_map, ARM_MAX_VQ);
> > > +    bitmap_zero(cpu->sve_vq_init, ARM_MAX_VQ);
> > > +    set_bit(0, cpu->sve_vq_map); /* 128bit */
> > > +    set_bit(0, cpu->sve_vq_init);
> > > +    set_bit(1, cpu->sve_vq_map); /* 256bit */
> > > +    set_bit(1, cpu->sve_vq_init);
> > > +    set_bit(3, cpu->sve_vq_map); /* 512bit */
> > > +    set_bit(3, cpu->sve_vq_init);
> > > +
> > > +    cpu->sve_max_vq = find_last_bit(cpu->sve_vq_map, ARM_MAX_VQ)
> +
> > > +1; }
> > > +
> > >  void arm_cpu_finalize_features(ARMCPU *cpu, Error **errp)  {
> > >      Error *local_err = NULL;
> > >
> > >      if (arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
> > > -        arm_cpu_sve_finalize(cpu, &local_err);
> > > -        if (local_err != NULL) {
> > > -            error_propagate(errp, local_err);
> > > -            return;
> > > +        if (arm_feature(&cpu->env, ARM_FEATURE_A64FX)) {
> > > +            a64fx_cpu_set_sve(cpu);
> > > +        } else {
> > > +            arm_cpu_sve_finalize(cpu, &local_err);
> > > +            if (local_err != NULL) {
> > > +                error_propagate(errp, local_err);
> > > +                return;
> > > +            }
> > >          }
> > >
> > >          /*
> > > diff --git a/target/arm/cpu.h b/target/arm/cpu.h index
> > > 9f0a5f84d5..84ebca731a 100644
> > > --- a/target/arm/cpu.h
> > > +++ b/target/arm/cpu.h
> > > @@ -2145,6 +2145,7 @@ enum arm_features {
> > >      ARM_FEATURE_M_SECURITY, /* M profile Security Extension */
> > >      ARM_FEATURE_M_MAIN, /* M profile Main Extension */
> > >      ARM_FEATURE_V8_1M, /* M profile extras only in v8.1M and later
> > > */
> > > +    ARM_FEATURE_A64FX, /* Fujitsu A64FX processor */
> > >  };
> > >
> > >  static inline int arm_feature(CPUARMState *env, int feature) diff
> > > --git a/target/arm/cpu64.c b/target/arm/cpu64.c index
> > > c690318a9b..5e7e885f9d 100644
> > > --- a/target/arm/cpu64.c
> > > +++ b/target/arm/cpu64.c
> > > @@ -847,10 +847,52 @@ static void aarch64_max_initfn(Object *obj)
> > >                          cpu_max_set_sve_max_vq, NULL, NULL);  }
> > >
> > > +static void aarch64_a64fx_initfn(Object *obj) {
> > > +    ARMCPU *cpu = ARM_CPU(obj);
> > > +
> > > +    cpu->dtb_compatible = "arm,a64fx";
> > > +    set_feature(&cpu->env, ARM_FEATURE_A64FX);
> > > +    set_feature(&cpu->env, ARM_FEATURE_V8);
> > > +    set_feature(&cpu->env, ARM_FEATURE_NEON);
> > > +    set_feature(&cpu->env, ARM_FEATURE_GENERIC_TIMER);
> > > +    set_feature(&cpu->env, ARM_FEATURE_AARCH64);
> > > +    set_feature(&cpu->env, ARM_FEATURE_EL2);
> > > +    set_feature(&cpu->env, ARM_FEATURE_EL3);
> > > +    set_feature(&cpu->env, ARM_FEATURE_PMU);
> > > +    cpu->midr = 0x461f0010;
> > > +    cpu->revidr = 0x00000000;
> > > +    cpu->ctr = 0x86668006;
> > > +    cpu->reset_sctlr = 0x30000180;
> > > +    cpu->isar.id_aa64pfr0 =   0x0000000101111111; /* No RAS
> Extensions */
> > > +    cpu->isar.id_aa64pfr1 = 0x0000000000000000;
> > > +    cpu->isar.id_aa64dfr0 = 0x0000000010305408;
> > > +    cpu->isar.id_aa64dfr1 = 0x0000000000000000;
> > > +    cpu->id_aa64afr0 = 0x0000000000000000;
> > > +    cpu->id_aa64afr1 = 0x0000000000000000;
> > > +    cpu->isar.id_aa64mmfr0 = 0x0000000000001122;
> > > +    cpu->isar.id_aa64mmfr1 = 0x0000000011212100;
> > > +    cpu->isar.id_aa64mmfr2 = 0x0000000000001011;
> > > +    cpu->isar.id_aa64isar0 = 0x0000000010211120;
> > > +    cpu->isar.id_aa64isar1 = 0x0000000000010001;
> > > +    cpu->isar.id_aa64zfr0 = 0x0000000000000000;
> > > +    cpu->clidr = 0x0000000080000023;
> > > +    cpu->ccsidr[0] = 0x7007e01c; /* 64KB L1 dcache */
> > > +    cpu->ccsidr[1] = 0x2007e01c; /* 64KB L1 icache */
> > > +    cpu->ccsidr[2] = 0x70ffe07c; /* 8MB L2 cache */
> > > +    cpu->dcz_blocksize = 6; /* 256 bytes */
> > > +    cpu->gic_num_lrs = 4;
> > > +    cpu->gic_vpribits = 5;
> > > +    cpu->gic_vprebits = 5;
> > > +
> > > +    /* TODO:  Add A64FX specific HPC extension registers */ }
> > > +
> > >  static const ARMCPUInfo aarch64_cpus[] = {
> > >      { .name = "cortex-a57",         .initfn = aarch64_a57_initfn },
> > >      { .name = "cortex-a53",         .initfn = aarch64_a53_initfn },
> > >      { .name = "cortex-a72",         .initfn = aarch64_a72_initfn },
> > > +    { .name = "a64fx",              .initfn = aarch64_a64fx_initfn },
> > >      { .name = "max",                .initfn = aarch64_max_initfn },
> > >  };
> > >
> > > --
> > > 2.27.0
> > >
> >
> > For the SVE related bits
> >
> > Reviewed-by: Andrew Jones <drjones@redhat.com>
> 
> On second thought, do we want the QMP CPU model expansion query to show that
> this CPU type has sve,sve128,sve256,sve512? If so, then our SVE work isn't
> complete, because we need those properties, set true by default, but forbidden
> from changing.
> 
> Thanks,
> drew