target/arm/cpu64: max cpu: Introduce sve<N> properties

Introduce cpu properties to give fine control over SVE vector lengths.
We introduce a property for each valid length up to the current
maximum supported, which is 2048-bits. The properties are named, e.g.
sve128, sve256, sve384, sve512, ..., where the number is the number of
bits. See the updates to docs/arm-cpu-features.rst for a description
of the semantics and for example uses.

Note, as sve-max-vq is still present and we'd like to be able to
support qmp_query_cpu_model_expansion with guests launched with e.g.
-cpu max,sve-max-vq=8 on their command lines, then we do allow
sve-max-vq and sve<N> properties to be provided at the same time, but
this is not recommended, and is why sve-max-vq is not mentioned in the
document.  If sve-max-vq is provided then it enables all lengths smaller
than and including the max and disables all lengths larger. It also has
the side-effect that no larger lengths may be enabled and that the max
itself cannot be disabled. Smaller non-power-of-two lengths may,
however, be disabled, e.g. -cpu max,sve-max-vq=4,sve384=off provides a
guest the vector lengths 128, 256, and 512 bits.

This patch has been co-authored with Richard Henderson, who reworked
the target/arm/cpu64.c changes in order to push all the validation and
auto-enabling/disabling steps into the finalizer, resulting in a nice
LOC reduction.

Signed-off-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Reviewed-by: Beata Michalska <beata.michalska@linaro.org>
Message-id: 20191031142734.8590-5-drjones@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 194 insertions, 0 deletions

diff --git a/tests/arm-cpu-features.c b/tests/arm-cpu-features.c
index 2ad9c2c..45fa3cb 100644
--- a/tests/arm-cpu-features.c
+++ b/tests/arm-cpu-features.c
@@ -9,10 +9,17 @@
  * See the COPYING file in the top-level directory.
  */
 #include "qemu/osdep.h"
+#include "qemu/bitops.h"
 #include "libqtest.h"
 #include "qapi/qmp/qdict.h"
 #include "qapi/qmp/qjson.h"
 
+/*
+ * We expect the SVE max-vq to be 16. Also it must be <= 64
+ * for our test code, otherwise 'vls' can't just be a uint64_t.
+ */
+#define SVE_MAX_VQ 16
+
 #define MACHINE     "-machine virt,gic-version=max,accel=tcg "
 #define MACHINE_KVM "-machine virt,gic-version=max,accel=kvm:tcg "
 #define QUERY_HEAD  "{ 'execute': 'query-cpu-model-expansion', " \
@@ -175,6 +182,183 @@ static void assert_bad_props(QTestState *qts, const char *cpu_type)
     qobject_unref(resp);
 }
 
+static uint64_t resp_get_sve_vls(QDict *resp)
+{
+    QDict *props;
+    const QDictEntry *e;
+    uint64_t vls = 0;
+    int n = 0;
+
+    g_assert(resp);
+    g_assert(resp_has_props(resp));
+
+    props = resp_get_props(resp);
+
+    for (e = qdict_first(props); e; e = qdict_next(props, e)) {
+        if (strlen(e->key) > 3 && !strncmp(e->key, "sve", 3) &&
+            g_ascii_isdigit(e->key[3])) {
+            char *endptr;
+            int bits;
+
+            bits = g_ascii_strtoll(&e->key[3], &endptr, 10);
+            if (!bits || *endptr != '\0') {
+                continue;
+            }
+
+            if (qdict_get_bool(props, e->key)) {
+                vls |= BIT_ULL((bits / 128) - 1);
+            }
+            ++n;
+        }
+    }
+
+    g_assert(n == SVE_MAX_VQ);
+
+    return vls;
+}
+
+#define assert_sve_vls(qts, cpu_type, expected_vls, fmt, ...)          \
+({                                                                     \
+    QDict *_resp = do_query(qts, cpu_type, fmt, ##__VA_ARGS__);        \
+    g_assert(_resp);                                                   \
+    g_assert(resp_has_props(_resp));                                   \
+    g_assert(resp_get_sve_vls(_resp) == expected_vls);                 \
+    qobject_unref(_resp);                                              \
+})
+
+static void sve_tests_default(QTestState *qts, const char *cpu_type)
+{
+    /*
+     * With no sve-max-vq or sve<N> properties on the command line
+     * the default is to have all vector lengths enabled. This also
+     * tests that 'sve' is 'on' by default.
+     */
+    assert_sve_vls(qts, cpu_type, BIT_ULL(SVE_MAX_VQ) - 1, NULL);
+
+    /* With SVE off, all vector lengths should also be off. */
+    assert_sve_vls(qts, cpu_type, 0, "{ 'sve': false }");
+
+    /* With SVE on, we must have at least one vector length enabled. */
+    assert_error(qts, cpu_type, "cannot disable sve128", "{ 'sve128': false }");
+
+    /* Basic enable/disable tests. */
+    assert_sve_vls(qts, cpu_type, 0x7, "{ 'sve384': true }");
+    assert_sve_vls(qts, cpu_type, ((BIT_ULL(SVE_MAX_VQ) - 1) & ~BIT_ULL(2)),
+                   "{ 'sve384': false }");
+
+    /*
+     * ---------------------------------------------------------------------
+     *               power-of-two(vq)   all-power-            can      can
+     *                                  of-two(< vq)        enable   disable
+     * ---------------------------------------------------------------------
+     * vq < max_vq      no                MUST*              yes      yes
+     * vq < max_vq      yes               MUST*              yes      no
+     * ---------------------------------------------------------------------
+     * vq == max_vq     n/a               MUST*              yes**    yes**
+     * ---------------------------------------------------------------------
+     * vq > max_vq      n/a               no                 no       yes
+     * vq > max_vq      n/a               yes                yes      yes
+     * ---------------------------------------------------------------------
+     *
+     * [*] "MUST" means this requirement must already be satisfied,
+     *     otherwise 'max_vq' couldn't itself be enabled.
+     *
+     * [**] Not testable with the QMP interface, only with the command line.
+     */
+
+    /* max_vq := 8 */
+    assert_sve_vls(qts, cpu_type, 0x8b, "{ 'sve1024': true }");
+
+    /* max_vq := 8, vq < max_vq, !power-of-two(vq) */
+    assert_sve_vls(qts, cpu_type, 0x8f,
+                   "{ 'sve1024': true, 'sve384': true }");
+    assert_sve_vls(qts, cpu_type, 0x8b,
+                   "{ 'sve1024': true, 'sve384': false }");
+
+    /* max_vq := 8, vq < max_vq, power-of-two(vq) */
+    assert_sve_vls(qts, cpu_type, 0x8b,
+                   "{ 'sve1024': true, 'sve256': true }");
+    assert_error(qts, cpu_type, "cannot disable sve256",
+                 "{ 'sve1024': true, 'sve256': false }");
+
+    /* max_vq := 3, vq > max_vq, !all-power-of-two(< vq) */
+    assert_error(qts, cpu_type, "cannot disable sve512",
+                 "{ 'sve384': true, 'sve512': false, 'sve640': true }");
+
+    /*
+     * We can disable power-of-two vector lengths when all larger lengths
+     * are also disabled. We only need to disable the power-of-two length,
+     * as all non-enabled larger lengths will then be auto-disabled.
+     */
+    assert_sve_vls(qts, cpu_type, 0x7, "{ 'sve512': false }");
+
+    /* max_vq := 3, vq > max_vq, all-power-of-two(< vq) */
+    assert_sve_vls(qts, cpu_type, 0x1f,
+                   "{ 'sve384': true, 'sve512': true, 'sve640': true }");
+    assert_sve_vls(qts, cpu_type, 0xf,
+                   "{ 'sve384': true, 'sve512': true, 'sve640': false }");
+}
+
+static void sve_tests_sve_max_vq_8(const void *data)
+{
+    QTestState *qts;
+
+    qts = qtest_init(MACHINE "-cpu max,sve-max-vq=8");
+
+    assert_sve_vls(qts, "max", BIT_ULL(8) - 1, NULL);
+
+    /*
+     * Disabling the max-vq set by sve-max-vq is not allowed, but
+     * of course enabling it is OK.
+     */
+    assert_error(qts, "max", "cannot disable sve1024", "{ 'sve1024': false }");
+    assert_sve_vls(qts, "max", 0xff, "{ 'sve1024': true }");
+
+    /*
+     * Enabling anything larger than max-vq set by sve-max-vq is not
+     * allowed, but of course disabling everything larger is OK.
+     */
+    assert_error(qts, "max", "cannot enable sve1152", "{ 'sve1152': true }");
+    assert_sve_vls(qts, "max", 0xff, "{ 'sve1152': false }");
+
+    /*
+     * We can enable/disable non power-of-two lengths smaller than the
+     * max-vq set by sve-max-vq, but, while we can enable power-of-two
+     * lengths, we can't disable them.
+     */
+    assert_sve_vls(qts, "max", 0xff, "{ 'sve384': true }");
+    assert_sve_vls(qts, "max", 0xfb, "{ 'sve384': false }");
+    assert_sve_vls(qts, "max", 0xff, "{ 'sve256': true }");
+    assert_error(qts, "max", "cannot disable sve256", "{ 'sve256': false }");
+
+    qtest_quit(qts);
+}
+
+static void sve_tests_sve_off(const void *data)
+{
+    QTestState *qts;
+
+    qts = qtest_init(MACHINE "-cpu max,sve=off");
+
+    /* SVE is off, so the map should be empty. */
+    assert_sve_vls(qts, "max", 0, NULL);
+
+    /* The map stays empty even if we turn lengths off. */
+    assert_sve_vls(qts, "max", 0, "{ 'sve128': false }");
+
+    /* It's an error to enable lengths when SVE is off. */
+    assert_error(qts, "max", "cannot enable sve128", "{ 'sve128': true }");
+
+    /* With SVE re-enabled we should get all vector lengths enabled. */
+    assert_sve_vls(qts, "max", BIT_ULL(SVE_MAX_VQ) - 1, "{ 'sve': true }");
+
+    /* Or enable SVE with just specific vector lengths. */
+    assert_sve_vls(qts, "max", 0x3,
+                   "{ 'sve': true, 'sve128': true, 'sve256': true }");
+
+    qtest_quit(qts);
+}
+
 static void test_query_cpu_model_expansion(const void *data)
 {
     QTestState *qts;
@@ -198,9 +382,12 @@ static void test_query_cpu_model_expansion(const void *data)
     if (g_str_equal(qtest_get_arch(), "aarch64")) {
         assert_has_feature(qts, "max", "aarch64");
         assert_has_feature(qts, "max", "sve");
+        assert_has_feature(qts, "max", "sve128");
         assert_has_feature(qts, "cortex-a57", "pmu");
         assert_has_feature(qts, "cortex-a57", "aarch64");
 
+        sve_tests_default(qts, "max");
+
         /* Test that features that depend on KVM generate errors without. */
         assert_error(qts, "max",
                      "'aarch64' feature cannot be disabled "
@@ -258,5 +445,12 @@ int main(int argc, char **argv)
                             NULL, test_query_cpu_model_expansion_kvm);
     }
 
+    if (g_str_equal(qtest_get_arch(), "aarch64")) {
+        qtest_add_data_func("/arm/max/query-cpu-model-expansion/sve-max-vq-8",
+                            NULL, sve_tests_sve_max_vq_8);
+        qtest_add_data_func("/arm/max/query-cpu-model-expansion/sve-off",
+                            NULL, sve_tests_sve_off);
+    }
+
     return g_test_run();
 }