diff mbox series

[v16,73/99] target/arm: cpu-sve: split TCG and KVM functionality

Message ID 20210604155312.15902-74-alex.bennee@linaro.org (mailing list archive)
State New, archived
Headers show
Series arm tcg/kvm refactor and split with kvm only support | expand

Commit Message

Alex Bennée June 4, 2021, 3:52 p.m. UTC
From: Claudio Fontana <cfontana@suse.de>

put the KVM-specific and TCG-specific functionality
in the respective subdirectories kvm/ and tcg/

Signed-off-by: Claudio Fontana <cfontana@suse.de>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 target/arm/kvm/kvm-sve.h   |  28 +++++++
 target/arm/tcg/tcg-sve.h   |  24 ++++++
 target/arm/cpu-sve.c       | 155 ++++++++++---------------------------
 target/arm/kvm/kvm-sve.c   | 118 ++++++++++++++++++++++++++++
 target/arm/tcg/tcg-sve.c   |  81 +++++++++++++++++++
 target/arm/kvm/meson.build |   1 +
 target/arm/tcg/meson.build |   1 +
 7 files changed, 296 insertions(+), 112 deletions(-)
 create mode 100644 target/arm/kvm/kvm-sve.h
 create mode 100644 target/arm/tcg/tcg-sve.h
 create mode 100644 target/arm/kvm/kvm-sve.c
 create mode 100644 target/arm/tcg/tcg-sve.c

Comments

Richard Henderson June 5, 2021, 7:31 p.m. UTC | #1
On 6/4/21 8:52 AM, Alex Bennée wrote:
>       DECLARE_BITMAP(kvm_supported, ARM_MAX_VQ);
> -    DECLARE_BITMAP(tmp, ARM_MAX_VQ);
> -    uint32_t vq, max_vq = 0;
> -
> -    /* Collect the set of vector lengths supported by KVM. */
> -    bitmap_zero(kvm_supported, ARM_MAX_VQ);
> -    if (kvm_enabled() && kvm_arm_sve_supported()) {
> -        kvm_arm_sve_get_vls(CPU(cpu), kvm_supported);
> -    } else if (kvm_enabled()) {
> -        assert(!cpu_isar_feature(aa64_sve, cpu));
> -    }
> +    uint32_t max_vq = 0;
>   
> +    if (kvm_enabled()) {
> +        kvm_sve_get_supported_lens(cpu, kvm_supported);
> +    }

Previously, kvm_supported was always initialized.

I guess this is sort-of a cleanup.  But we've got 4 different checks for kvm 
and tcg.  I think we can actually tidy this up with a set of callbacks.

static bool do_sve_finalize(ARMCPU *cpu, Error **errp,
     void (*get_supported_lens)(ARMCPU *, unsigned long *),
     void (*enable_lens)(unsigned long *vq_map,
                         unsigned long *vq_init,
                         uint32_t max_vq,
                         unsigned long *supported),
     void (*disable_lens)(unsigned long *vq_map,
                          unsigned long *vq_init,
                          unsigned long *supported,
                          Error **errp),
     void (*validate_lens)(unsigned long *vq_map,
                           unsigned long *vq_init,
                           unsigned long *supported,
                           Error **errp, uint32_t max_vq))
{
     ...
}

bool cpu_sve_finalize_features(ARMCPU *cpu, Error **errp)
{
     if (kvm_enabled()) {
         return do_sve_finalize(cpu, errp,
                                kvm_sve_get_supported_lens,
                                kvm_sve_enable_lens,
                                kvm_sve_disable_lens,
                                kvm_sve_validate_lens);
     } else if (tcg_enabled()) {
         return do_sve_finalize(cpu, errp,
                                tcg_sve_get_supported_lens,
                                tcg_sve_enable_lens,
                                tcg_sve_disable_lens,
                                tcg_sve_validate_lens);
     } else {
         g_assert_not_reached(); /* ??? */
     }
}

with

void tcg_sve_get_supported_lens(ARMCPU *cpu,
                                 unsigned long *supported)
{
     bitmap_fill(supported, ARM_MAX_VQ);
}

which we can later adjust for, e.g. -cpu a64fx and neoverse-v1, etc, which 
don't support all vq sizes.


r~
Richard Henderson June 5, 2021, 7:52 p.m. UTC | #2
On 6/4/21 8:52 AM, Alex Bennée wrote:
> +void kvm_sve_get_supported_lens(ARMCPU *cpu, unsigned long *kvm_supported)
> +{
> +    /* Collect the set of vector lengths supported by KVM. */
> +    bitmap_zero(kvm_supported, ARM_MAX_VQ);
> +
> +    if (kvm_arm_sve_supported()) {
> +        kvm_arm_sve_get_vls(CPU(cpu), kvm_supported);
> +    } else {
> +        assert(!cpu_isar_feature(aa64_sve, cpu));
> +    }
> +}
> +
> +void kvm_sve_enable_lens(unsigned long *sve_vq_map,
> +                         unsigned long *sve_vq_init, uint32_t max_vq,
> +                         unsigned long *kvm_supported)
> +{
> +    /*
> +     * For KVM we have to automatically enable all supported unitialized
> +     * lengths, even when the smaller lengths are not all powers-of-two.
> +     */
> +    DECLARE_BITMAP(tmp, ARM_MAX_VQ);
> +
> +    bitmap_andnot(tmp, kvm_supported, sve_vq_init, max_vq);
> +    bitmap_or(sve_vq_map, sve_vq_map, tmp, max_vq);
> +}
> +
> +uint32_t kvm_sve_disable_lens(unsigned long *sve_vq_map,
> +                              unsigned long *sve_vq_init,
> +                              unsigned long *kvm_supported, Error **errp)
> +{
> +    uint32_t max_vq, vq;
> +
> +    /* Disabling a supported length disables all larger lengths. */
> +    for (vq = 1; vq <= ARM_MAX_VQ; ++vq) {
> +        if (test_bit(vq - 1, sve_vq_init) &&
> +            test_bit(vq - 1, kvm_supported)) {
> +            break;
> +        }
> +    }
> +
> +    max_vq = vq <= ARM_MAX_VQ ? vq - 1 : ARM_MAX_VQ;
> +    bitmap_andnot(sve_vq_map, kvm_supported, sve_vq_init, max_vq);
> +
> +    if (max_vq == 0 || bitmap_empty(sve_vq_map, max_vq)) {
> +        error_setg(errp, "cannot disable sve%d", vq * 128);
> +        error_append_hint(errp, "Disabling sve%d results in all "
> +                          "vector lengths being disabled.\n",
> +                          vq * 128);
> +        error_append_hint(errp, "With SVE enabled, at least one "
> +                          "vector length must be enabled.\n");
> +        return 0;
> +    }
> +
> +    return max_vq;
> +}
> +
> +bool kvm_sve_validate_lens(unsigned long *sve_vq_map, uint32_t max_vq,
> +                           unsigned long *kvm_supported, Error **errp,
> +                           uint32_t sve_max_vq)
> +{
> +    /* Ensure the set of lengths matches what KVM supports. */
> +    DECLARE_BITMAP(tmp, ARM_MAX_VQ);
> +    uint32_t vq;
> +
> +    bitmap_xor(tmp, sve_vq_map, kvm_supported, max_vq);
> +    if (bitmap_empty(tmp, max_vq)) {
> +        return true;
> +    }
> +
> +    vq = find_last_bit(tmp, max_vq) + 1;
> +    if (test_bit(vq - 1, sve_vq_map)) {
> +        if (sve_max_vq) {
> +            error_setg(errp, "cannot set sve-max-vq=%d", sve_max_vq);
> +            error_append_hint(errp, "This KVM host does not support "
> +                              "the vector length %d-bits.\n", vq * 128);
> +            error_append_hint(errp, "It may not be possible to use "
> +                              "sve-max-vq with this KVM host. Try "
> +                              "using only sve<N> properties.\n");
> +        } else {
> +            error_setg(errp, "cannot enable sve%d", vq * 128);
> +            error_append_hint(errp, "This KVM host does not support "
> +                              "the vector length %d-bits.\n", vq * 128);
> +        }
> +    } else {
> +        error_setg(errp, "cannot disable sve%d", vq * 128);
> +        error_append_hint(errp, "The KVM host requires all "
> +                          "supported vector lengths smaller "
> +                          "than %d bits to also be enabled.\n", max_vq * 128);
> +    }
> +    return false;
> +}

Also, I think I mentioned this before in review of a previous version, I 
strongly suspect that aside from kvm_sve_get_supported_lens, the other 
functions will be used without change by all other hw virt systems.

So I think we'll do best, short term, to keep all of this in cpu-sve.c for now. 
  The tcg_enabled() test should elide all of the code that's not needed when 
!CONFIG_TCG.


r~
diff mbox series

Patch

diff --git a/target/arm/kvm/kvm-sve.h b/target/arm/kvm/kvm-sve.h
new file mode 100644
index 0000000000..9a9556b916
--- /dev/null
+++ b/target/arm/kvm/kvm-sve.h
@@ -0,0 +1,28 @@ 
+/*
+ * QEMU AArch64 CPU SVE KVM interface
+ *
+ * Copyright 2021 SUSE LLC
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef KVM_SVE_H
+#define KVM_SVE_H
+
+void kvm_sve_get_supported_lens(ARMCPU *cpu,
+                                unsigned long *kvm_supported);
+
+void kvm_sve_enable_lens(unsigned long *sve_vq_map,
+                         unsigned long *sve_vq_init, uint32_t max_vq,
+                         unsigned long *kvm_supported);
+
+uint32_t kvm_sve_disable_lens(unsigned long *sve_vq_map,
+                              unsigned long *sve_vq_init,
+                              unsigned long *kvm_supported, Error **errp);
+
+bool kvm_sve_validate_lens(unsigned long *sve_vq_map, uint32_t max_vq,
+                           unsigned long *kvm_supported, Error **errp,
+                           uint32_t sve_max_vq);
+
+#endif /* KVM_SVE_H */
diff --git a/target/arm/tcg/tcg-sve.h b/target/arm/tcg/tcg-sve.h
new file mode 100644
index 0000000000..4bed809b9a
--- /dev/null
+++ b/target/arm/tcg/tcg-sve.h
@@ -0,0 +1,24 @@ 
+/*
+ * QEMU AArch64 CPU SVE TCG interface
+ *
+ * Copyright 2021 SUSE LLC
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef TCG_SVE_H
+#define TCG_SVE_H
+
+/* note: SVE is an AARCH64-only option, only include this for TARGET_AARCH64 */
+
+void tcg_sve_enable_lens(unsigned long *sve_vq_map,
+                         unsigned long *sve_vq_init, uint32_t max_vq);
+
+uint32_t tcg_sve_disable_lens(unsigned long *sve_vq_map,
+                              unsigned long *sve_vq_init, Error **errp);
+
+bool tcg_sve_validate_lens(unsigned long *sve_vq_map, uint32_t max_vq,
+                           Error **errp);
+
+#endif /* TCG_SVE_H */
diff --git a/target/arm/cpu-sve.c b/target/arm/cpu-sve.c
index da60330cc2..5190e4a639 100644
--- a/target/arm/cpu-sve.c
+++ b/target/arm/cpu-sve.c
@@ -27,6 +27,28 @@ 
 #include "qapi/visitor.h"
 #include "cpu-sve.h"
 
+#include "tcg/tcg-sve.h"
+#include "kvm/kvm-sve.h"
+
+static bool apply_max_vq(unsigned long *sve_vq_map, unsigned long *sve_vq_init,
+                         uint32_t max_vq, Error **errp)
+{
+    DECLARE_BITMAP(tmp, ARM_MAX_VQ);
+
+    if (!test_bit(max_vq - 1, sve_vq_map) &&
+        test_bit(max_vq - 1, sve_vq_init)) {
+        error_setg(errp, "cannot disable sve%d", max_vq * 128);
+        error_append_hint(errp, "The maximum vector length must be "
+                          "enabled, sve-max-vq=%d (%d bits)\n",
+                          max_vq, max_vq * 128);
+        return false;
+    }
+    /* Set all bits not explicitly set within sve-max-vq. */
+    bitmap_complement(tmp, sve_vq_init, max_vq);
+    bitmap_or(sve_vq_map, sve_vq_map, tmp, max_vq);
+    return true;
+}
+
 void cpu_sve_finalize_features(ARMCPU *cpu, Error **errp)
 {
     /*
@@ -45,17 +67,11 @@  void cpu_sve_finalize_features(ARMCPU *cpu, Error **errp)
      * vector length must be enabled.
      */
     DECLARE_BITMAP(kvm_supported, ARM_MAX_VQ);
-    DECLARE_BITMAP(tmp, ARM_MAX_VQ);
-    uint32_t vq, max_vq = 0;
-
-    /* Collect the set of vector lengths supported by KVM. */
-    bitmap_zero(kvm_supported, ARM_MAX_VQ);
-    if (kvm_enabled() && kvm_arm_sve_supported()) {
-        kvm_arm_sve_get_vls(CPU(cpu), kvm_supported);
-    } else if (kvm_enabled()) {
-        assert(!cpu_isar_feature(aa64_sve, cpu));
-    }
+    uint32_t max_vq = 0;
 
+    if (kvm_enabled()) {
+        kvm_sve_get_supported_lens(cpu, kvm_supported);
+    }
     /*
      * Process explicit sve<N> properties.
      * From the properties, sve_vq_map<N> implies sve_vq_init<N>.
@@ -72,70 +88,28 @@  void cpu_sve_finalize_features(ARMCPU *cpu, Error **errp)
                               cpu->sve_max_vq * 128);
             return;
         }
-
         if (kvm_enabled()) {
-            /*
-             * For KVM we have to automatically enable all supported unitialized
-             * lengths, even when the smaller lengths are not all powers-of-two.
-             */
-            bitmap_andnot(tmp, kvm_supported, cpu->sve_vq_init, max_vq);
-            bitmap_or(cpu->sve_vq_map, cpu->sve_vq_map, tmp, max_vq);
+            kvm_sve_enable_lens(cpu->sve_vq_map, cpu->sve_vq_init, max_vq,
+                                kvm_supported);
         } else if (tcg_enabled()) {
-            /* Propagate enabled bits down through required powers-of-two. */
-            for (vq = pow2floor(max_vq); vq >= 1; vq >>= 1) {
-                if (!test_bit(vq - 1, cpu->sve_vq_init)) {
-                    set_bit(vq - 1, cpu->sve_vq_map);
-                }
-            }
+            tcg_sve_enable_lens(cpu->sve_vq_map, cpu->sve_vq_init, max_vq);
         }
     } else if (cpu->sve_max_vq == 0) {
-        /*
-         * No explicit bits enabled, and no implicit bits from sve-max-vq.
-         */
+        /* No explicit bits enabled, and no implicit bits from sve-max-vq. */
         if (!cpu_isar_feature(aa64_sve, cpu)) {
             /* SVE is disabled and so are all vector lengths.  Good. */
             return;
         }
-
         if (kvm_enabled()) {
-            /* Disabling a supported length disables all larger lengths. */
-            for (vq = 1; vq <= ARM_MAX_VQ; ++vq) {
-                if (test_bit(vq - 1, cpu->sve_vq_init) &&
-                    test_bit(vq - 1, kvm_supported)) {
-                    break;
-                }
-            }
-            max_vq = vq <= ARM_MAX_VQ ? vq - 1 : ARM_MAX_VQ;
-            bitmap_andnot(cpu->sve_vq_map, kvm_supported,
-                          cpu->sve_vq_init, max_vq);
-            if (max_vq == 0 || bitmap_empty(cpu->sve_vq_map, max_vq)) {
-                error_setg(errp, "cannot disable sve%d", vq * 128);
-                error_append_hint(errp, "Disabling sve%d results in all "
-                                  "vector lengths being disabled.\n",
-                                  vq * 128);
-                error_append_hint(errp, "With SVE enabled, at least one "
-                                  "vector length must be enabled.\n");
-                return;
-            }
+            max_vq = kvm_sve_disable_lens(cpu->sve_vq_map, cpu->sve_vq_init,
+                                          kvm_supported, errp);
         } else if (tcg_enabled()) {
-            /* Disabling a power-of-two disables all larger lengths. */
-            if (test_bit(0, cpu->sve_vq_init)) {
-                error_setg(errp, "cannot disable sve128");
-                error_append_hint(errp, "Disabling sve128 results in all "
-                                  "vector lengths being disabled.\n");
-                error_append_hint(errp, "With SVE enabled, at least one "
-                                  "vector length must be enabled.\n");
-                return;
-            }
-            for (vq = 2; vq <= ARM_MAX_VQ; vq <<= 1) {
-                if (test_bit(vq - 1, cpu->sve_vq_init)) {
-                    break;
-                }
-            }
-            max_vq = vq <= ARM_MAX_VQ ? vq - 1 : ARM_MAX_VQ;
-            bitmap_complement(cpu->sve_vq_map, cpu->sve_vq_init, max_vq);
+            max_vq = tcg_sve_disable_lens(cpu->sve_vq_map, cpu->sve_vq_init,
+                                          errp);
+        }
+        if (!max_vq) {
+            return;
         }
-
         max_vq = find_last_bit(cpu->sve_vq_map, max_vq) + 1;
     }
 
@@ -146,21 +120,11 @@  void cpu_sve_finalize_features(ARMCPU *cpu, Error **errp)
      */
     if (cpu->sve_max_vq != 0) {
         max_vq = cpu->sve_max_vq;
-
-        if (!test_bit(max_vq - 1, cpu->sve_vq_map) &&
-            test_bit(max_vq - 1, cpu->sve_vq_init)) {
-            error_setg(errp, "cannot disable sve%d", max_vq * 128);
-            error_append_hint(errp, "The maximum vector length must be "
-                              "enabled, sve-max-vq=%d (%d bits)\n",
-                              max_vq, max_vq * 128);
+        if (!apply_max_vq(cpu->sve_vq_map, cpu->sve_vq_init, max_vq,
+                          errp)) {
             return;
         }
-
-        /* Set all bits not explicitly set within sve-max-vq. */
-        bitmap_complement(tmp, cpu->sve_vq_init, max_vq);
-        bitmap_or(cpu->sve_vq_map, cpu->sve_vq_map, tmp, max_vq);
     }
-
     /*
      * We should know what max-vq is now.  Also, as we're done
      * manipulating sve-vq-map, we ensure any bits above max-vq
@@ -170,46 +134,13 @@  void cpu_sve_finalize_features(ARMCPU *cpu, Error **errp)
     bitmap_clear(cpu->sve_vq_map, max_vq, ARM_MAX_VQ - max_vq);
 
     if (kvm_enabled()) {
-        /* Ensure the set of lengths matches what KVM supports. */
-        bitmap_xor(tmp, cpu->sve_vq_map, kvm_supported, max_vq);
-        if (!bitmap_empty(tmp, max_vq)) {
-            vq = find_last_bit(tmp, max_vq) + 1;
-            if (test_bit(vq - 1, cpu->sve_vq_map)) {
-                if (cpu->sve_max_vq) {
-                    error_setg(errp, "cannot set sve-max-vq=%d",
-                               cpu->sve_max_vq);
-                    error_append_hint(errp, "This KVM host does not support "
-                                      "the vector length %d-bits.\n",
-                                      vq * 128);
-                    error_append_hint(errp, "It may not be possible to use "
-                                      "sve-max-vq with this KVM host. Try "
-                                      "using only sve<N> properties.\n");
-                } else {
-                    error_setg(errp, "cannot enable sve%d", vq * 128);
-                    error_append_hint(errp, "This KVM host does not support "
-                                      "the vector length %d-bits.\n",
-                                      vq * 128);
-                }
-            } else {
-                error_setg(errp, "cannot disable sve%d", vq * 128);
-                error_append_hint(errp, "The KVM host requires all "
-                                  "supported vector lengths smaller "
-                                  "than %d bits to also be enabled.\n",
-                                  max_vq * 128);
-            }
+        if (!kvm_sve_validate_lens(cpu->sve_vq_map, max_vq, kvm_supported,
+                                   errp, cpu->sve_max_vq)) {
             return;
         }
     } else if (tcg_enabled()) {
-        /* Ensure all required powers-of-two are enabled. */
-        for (vq = pow2floor(max_vq); vq >= 1; vq >>= 1) {
-            if (!test_bit(vq - 1, cpu->sve_vq_map)) {
-                error_setg(errp, "cannot disable sve%d", vq * 128);
-                error_append_hint(errp, "sve%d is required as it "
-                                  "is a power-of-two length smaller than "
-                                  "the maximum, sve%d\n",
-                                  vq * 128, max_vq * 128);
-                return;
-            }
+        if (!tcg_sve_validate_lens(cpu->sve_vq_map, max_vq, errp)) {
+            return;
         }
     }
 
diff --git a/target/arm/kvm/kvm-sve.c b/target/arm/kvm/kvm-sve.c
new file mode 100644
index 0000000000..21dfee5b5c
--- /dev/null
+++ b/target/arm/kvm/kvm-sve.c
@@ -0,0 +1,118 @@ 
+/*
+ * QEMU ARM CPU
+ *
+ * Copyright (c) 2012 SUSE LINUX Products GmbH
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see
+ * <http://www.gnu.org/licenses/gpl-2.0.html>
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "cpu.h"
+#include "sysemu/kvm.h"
+#include "kvm/kvm_arm.h"
+#include "kvm/kvm-sve.h"
+
+void kvm_sve_get_supported_lens(ARMCPU *cpu, unsigned long *kvm_supported)
+{
+    /* Collect the set of vector lengths supported by KVM. */
+    bitmap_zero(kvm_supported, ARM_MAX_VQ);
+
+    if (kvm_arm_sve_supported()) {
+        kvm_arm_sve_get_vls(CPU(cpu), kvm_supported);
+    } else {
+        assert(!cpu_isar_feature(aa64_sve, cpu));
+    }
+}
+
+void kvm_sve_enable_lens(unsigned long *sve_vq_map,
+                         unsigned long *sve_vq_init, uint32_t max_vq,
+                         unsigned long *kvm_supported)
+{
+    /*
+     * For KVM we have to automatically enable all supported unitialized
+     * lengths, even when the smaller lengths are not all powers-of-two.
+     */
+    DECLARE_BITMAP(tmp, ARM_MAX_VQ);
+
+    bitmap_andnot(tmp, kvm_supported, sve_vq_init, max_vq);
+    bitmap_or(sve_vq_map, sve_vq_map, tmp, max_vq);
+}
+
+uint32_t kvm_sve_disable_lens(unsigned long *sve_vq_map,
+                              unsigned long *sve_vq_init,
+                              unsigned long *kvm_supported, Error **errp)
+{
+    uint32_t max_vq, vq;
+
+    /* Disabling a supported length disables all larger lengths. */
+    for (vq = 1; vq <= ARM_MAX_VQ; ++vq) {
+        if (test_bit(vq - 1, sve_vq_init) &&
+            test_bit(vq - 1, kvm_supported)) {
+            break;
+        }
+    }
+
+    max_vq = vq <= ARM_MAX_VQ ? vq - 1 : ARM_MAX_VQ;
+    bitmap_andnot(sve_vq_map, kvm_supported, sve_vq_init, max_vq);
+
+    if (max_vq == 0 || bitmap_empty(sve_vq_map, max_vq)) {
+        error_setg(errp, "cannot disable sve%d", vq * 128);
+        error_append_hint(errp, "Disabling sve%d results in all "
+                          "vector lengths being disabled.\n",
+                          vq * 128);
+        error_append_hint(errp, "With SVE enabled, at least one "
+                          "vector length must be enabled.\n");
+        return 0;
+    }
+
+    return max_vq;
+}
+
+bool kvm_sve_validate_lens(unsigned long *sve_vq_map, uint32_t max_vq,
+                           unsigned long *kvm_supported, Error **errp,
+                           uint32_t sve_max_vq)
+{
+    /* Ensure the set of lengths matches what KVM supports. */
+    DECLARE_BITMAP(tmp, ARM_MAX_VQ);
+    uint32_t vq;
+
+    bitmap_xor(tmp, sve_vq_map, kvm_supported, max_vq);
+    if (bitmap_empty(tmp, max_vq)) {
+        return true;
+    }
+
+    vq = find_last_bit(tmp, max_vq) + 1;
+    if (test_bit(vq - 1, sve_vq_map)) {
+        if (sve_max_vq) {
+            error_setg(errp, "cannot set sve-max-vq=%d", sve_max_vq);
+            error_append_hint(errp, "This KVM host does not support "
+                              "the vector length %d-bits.\n", vq * 128);
+            error_append_hint(errp, "It may not be possible to use "
+                              "sve-max-vq with this KVM host. Try "
+                              "using only sve<N> properties.\n");
+        } else {
+            error_setg(errp, "cannot enable sve%d", vq * 128);
+            error_append_hint(errp, "This KVM host does not support "
+                              "the vector length %d-bits.\n", vq * 128);
+        }
+    } else {
+        error_setg(errp, "cannot disable sve%d", vq * 128);
+        error_append_hint(errp, "The KVM host requires all "
+                          "supported vector lengths smaller "
+                          "than %d bits to also be enabled.\n", max_vq * 128);
+    }
+    return false;
+}
diff --git a/target/arm/tcg/tcg-sve.c b/target/arm/tcg/tcg-sve.c
new file mode 100644
index 0000000000..99cfde1f41
--- /dev/null
+++ b/target/arm/tcg/tcg-sve.c
@@ -0,0 +1,81 @@ 
+/*
+ * QEMU ARM CPU
+ *
+ * Copyright (c) 2012 SUSE LINUX Products GmbH
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see
+ * <http://www.gnu.org/licenses/gpl-2.0.html>
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "cpu.h"
+#include "sysemu/tcg.h"
+#include "cpu-sve.h"
+#include "tcg-sve.h"
+
+void tcg_sve_enable_lens(unsigned long *sve_vq_map,
+                         unsigned long *sve_vq_init, uint32_t max_vq)
+{
+    /* Propagate enabled bits down through required powers-of-two. */
+    uint32_t vq;
+
+    for (vq = pow2floor(max_vq); vq >= 1; vq >>= 1) {
+        if (!test_bit(vq - 1, sve_vq_init)) {
+            set_bit(vq - 1, sve_vq_map);
+        }
+    }
+}
+
+uint32_t tcg_sve_disable_lens(unsigned long *sve_vq_map,
+                              unsigned long *sve_vq_init, Error **errp)
+{
+    /* Disabling a power-of-two disables all larger lengths. */
+    uint32_t max_vq, vq;
+
+    if (test_bit(0, sve_vq_init)) {
+        error_setg(errp, "cannot disable sve128");
+        error_append_hint(errp, "Disabling sve128 results in all "
+                          "vector lengths being disabled.\n");
+        error_append_hint(errp, "With SVE enabled, at least one "
+                          "vector length must be enabled.\n");
+        return 0;
+    }
+    for (vq = 2; vq <= ARM_MAX_VQ; vq <<= 1) {
+        if (test_bit(vq - 1, sve_vq_init)) {
+            break;
+        }
+    }
+    max_vq = vq <= ARM_MAX_VQ ? vq - 1 : ARM_MAX_VQ;
+    bitmap_complement(sve_vq_map, sve_vq_init, max_vq);
+    return max_vq;
+}
+
+bool tcg_sve_validate_lens(unsigned long *sve_vq_map, uint32_t max_vq,
+                           Error **errp)
+{
+    /* Ensure all required powers-of-two are enabled. */
+    uint32_t vq;
+
+    for (vq = pow2floor(max_vq); vq >= 1; vq >>= 1) {
+        if (!test_bit(vq - 1, sve_vq_map)) {
+            error_setg(errp, "cannot disable sve%d", vq * 128);
+            error_append_hint(errp, "sve%d is required as it "
+                              "is a power-of-two length smaller than "
+                              "the maximum, sve%d\n", vq * 128, max_vq * 128);
+            return false;
+        }
+    }
+    return true;
+}
diff --git a/target/arm/kvm/meson.build b/target/arm/kvm/meson.build
index ef58a29dd7..1ae62bd65c 100644
--- a/target/arm/kvm/meson.build
+++ b/target/arm/kvm/meson.build
@@ -2,4 +2,5 @@  arm_ss.add(when: 'CONFIG_KVM', if_true: files(
   'kvm.c',
   'kvm64.c',
   'kvm-cpu.c',
+  'kvm-sve.c',
 ))
diff --git a/target/arm/tcg/meson.build b/target/arm/tcg/meson.build
index 5b36a13a24..c289771e97 100644
--- a/target/arm/tcg/meson.build
+++ b/target/arm/tcg/meson.build
@@ -45,6 +45,7 @@  arm_ss.add(when: ['TARGET_AARCH64','CONFIG_TCG'], if_true: files(
   'mte_helper.c',
   'pauth_helper.c',
   'sve_helper.c',
+  'tcg-sve.c',
 ))
 
 subdir('user')