[PATCH v7 06/11] libs/guest: introduce helper set cpu topology in cpu policy

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

This logic is pulled out from xc_cpuid_apply_policy and placed into a
separate helper. Note the legacy part of the introduced function, as
long term Xen will require a proper topology setter function capable
of expressing a more diverse set of topologies.

No functional change intended.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Changes since v6:
 - Pass a host policy to xc_cpu_policy_legacy_topology.

Changes since v5:
 - Keep using the host featureset.
 - Fix copied comment typo.

Changes since v4:
 - s/xc_cpu_policy_topology/xc_cpu_policy_legacy_topology/
---
 tools/include/xenguest.h        |   9 ++
 tools/libs/guest/xg_cpuid_x86.c | 165 ++++++++++++++++----------------
 2 files changed, 91 insertions(+), 83 deletions(-)

diff --git a/tools/include/xenguest.h b/tools/include/xenguest.h
index df18c73984..5e60f81192 100644
--- a/tools/include/xenguest.h
+++ b/tools/include/xenguest.h
@@ -821,6 +821,15 @@ bool xc_cpu_policy_is_compatible(xc_interface *xch, 
xc_cpu_policy_t *host,
 void xc_cpu_policy_make_compat_4_12(xc_interface *xch, xc_cpu_policy_t *policy,
                                     const xc_cpu_policy_t *host, bool hvm);
 
+/*
+ * Setup the legacy policy topology.
+ *
+ * The `host` parameter should only be provided when creating a policy for a PV
+ * guest.
+ */
+void xc_cpu_policy_legacy_topology(xc_interface *xch, xc_cpu_policy_t *policy,
+                                   const xc_cpu_policy_t *host);
+
 int xc_get_cpu_levelling_caps(xc_interface *xch, uint32_t *caps);
 int xc_get_cpu_featureset(xc_interface *xch, uint32_t index,
                           uint32_t *nr_features, uint32_t *featureset);
diff --git a/tools/libs/guest/xg_cpuid_x86.c b/tools/libs/guest/xg_cpuid_x86.c
index 20fd786da3..6d8d16eed5 100644
--- a/tools/libs/guest/xg_cpuid_x86.c
+++ b/tools/libs/guest/xg_cpuid_x86.c
@@ -429,14 +429,12 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t 
domid, bool restore,
 {
     int rc;
     xc_dominfo_t di;
-    unsigned int i, nr_leaves, nr_msrs;
+    unsigned int nr_leaves, nr_msrs;
     xen_cpuid_leaf_t *leaves = NULL;
     struct cpuid_policy *p = NULL;
     xc_cpu_policy_t *policy = NULL;
     xc_cpu_policy_t *host = NULL;
     uint32_t err_leaf = -1, err_subleaf = -1, err_msr = -1;
-    uint32_t host_featureset[FEATURESET_NR_ENTRIES] = {};
-    uint32_t len = ARRAY_SIZE(host_featureset);
 
     if ( xc_domain_getinfo(xch, domid, 1, &di) != 1 ||
          di.domid != domid )
@@ -461,24 +459,14 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t 
domid, bool restore,
          (host = xc_cpu_policy_init()) == NULL )
         goto out;
 
-    /* Get the host policy. */
-    rc = xc_get_cpu_featureset(xch, XEN_SYSCTL_cpu_featureset_host,
-                               &len, host_featureset);
+    rc = xc_cpu_policy_get_system(xch, XEN_SYSCTL_cpu_policy_host, host);
     if ( rc )
     {
-        /* Tolerate "buffer too small", as we've got the bits we need. */
-        if ( errno == ENOBUFS )
-            rc = 0;
-        else
-        {
-            PERROR("Failed to obtain host featureset");
-            rc = -errno;
-            goto out;
-        }
+        PERROR("Failed to get host policy");
+        rc = -errno;
+        goto out;
     }
 
-    cpuid_featureset_to_policy(host_featureset, &host->cpuid);
-
     /* Get the domain's default policy. */
     nr_msrs = 0;
     rc = get_system_cpu_policy(xch, di.hvm ? XEN_SYSCTL_cpu_policy_hvm_default
@@ -562,72 +550,9 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t 
domid, bool restore,
         }
     }
 
-    if ( !di.hvm )
-    {
-        /*
-         * On hardware without CPUID Faulting, PV guests see real topology.
-         * As a consequence, they also need to see the host htt/cmp fields.
-         */
-        p->basic.htt       = test_bit(X86_FEATURE_HTT, host_featureset);
-        p->extd.cmp_legacy = test_bit(X86_FEATURE_CMP_LEGACY, host_featureset);
-    }
-    else
-    {
-        /*
-         * Topology for HVM guests is entirely controlled by Xen.  For now, we
-         * hardcode APIC_ID = vcpu_id * 2 to give the illusion of no SMT.
-         */
-        p->basic.htt = true;
-        p->extd.cmp_legacy = false;
-
-        /*
-         * Leaf 1 EBX[23:16] is Maximum Logical Processors Per Package.
-         * Update to reflect vLAPIC_ID = vCPU_ID * 2, but make sure to avoid
-         * overflow.
-         */
-        if ( !p->basic.lppp )
-            p->basic.lppp = 2;
-        else if ( !(p->basic.lppp & 0x80) )
-            p->basic.lppp *= 2;
-
-        switch ( p->x86_vendor )
-        {
-        case X86_VENDOR_INTEL:
-            for ( i = 0; (p->cache.subleaf[i].type &&
-                          i < ARRAY_SIZE(p->cache.raw)); ++i )
-            {
-                p->cache.subleaf[i].cores_per_package =
-                    (p->cache.subleaf[i].cores_per_package << 1) | 1;
-                p->cache.subleaf[i].threads_per_cache = 0;
-            }
-            break;
-
-        case X86_VENDOR_AMD:
-        case X86_VENDOR_HYGON:
-            /*
-             * Leaf 0x80000008 ECX[15:12] is ApicIdCoreSize.
-             * Leaf 0x80000008 ECX[7:0] is NumberOfCores (minus one).
-             * Update to reflect vLAPIC_ID = vCPU_ID * 2.  But avoid
-             * - overflow,
-             * - going out of sync with leaf 1 EBX[23:16],
-             * - incrementing ApicIdCoreSize when it's zero (which changes the
-             *   meaning of bits 7:0).
-             *
-             * UPDATE: I addition to avoiding overflow, some
-             * proprietary operating systems have trouble with
-             * apic_id_size values greater than 7.  Limit the value to
-             * 7 for now.
-             */
-            if ( p->extd.nc < 0x7f )
-            {
-                if ( p->extd.apic_id_size != 0 && p->extd.apic_id_size < 0x7 )
-                    p->extd.apic_id_size++;
-
-                p->extd.nc = (p->extd.nc << 1) | 1;
-            }
-            break;
-        }
-    }
+    policy->cpuid = *p;
+    xc_cpu_policy_legacy_topology(xch, policy, di.hvm ? NULL : host);
+    *p = policy->cpuid;
 
     rc = x86_cpuid_copy_to_buffer(p, leaves, &nr_leaves);
     if ( rc )
@@ -933,3 +858,77 @@ void xc_cpu_policy_make_compat_4_12(xc_interface *xch, 
xc_cpu_policy_t *policy,
     policy->cpuid.feat.max_subleaf = 0;
     policy->cpuid.extd.max_leaf = min(policy->cpuid.extd.max_leaf, 0x8000001c);
 }
+
+void xc_cpu_policy_legacy_topology(xc_interface *xch, xc_cpu_policy_t *policy,
+                                   const xc_cpu_policy_t *host)
+{
+    if ( host )
+    {
+        /*
+         * On hardware without CPUID Faulting, PV guests see real topology.
+         * As a consequence, they also need to see the host htt/cmp fields.
+         */
+        policy->cpuid.basic.htt = host->cpuid.basic.htt;
+        policy->cpuid.extd.cmp_legacy = host->cpuid.extd.cmp_legacy;
+    }
+    else
+    {
+        unsigned int i;
+
+        /*
+         * Topology for HVM guests is entirely controlled by Xen.  For now, we
+         * hardcode APIC_ID = vcpu_id * 2 to give the illusion of no SMT.
+         */
+        policy->cpuid.basic.htt = true;
+        policy->cpuid.extd.cmp_legacy = false;
+
+        /*
+         * Leaf 1 EBX[23:16] is Maximum Logical Processors Per Package.
+         * Update to reflect vLAPIC_ID = vCPU_ID * 2, but make sure to avoid
+         * overflow.
+         */
+        if ( !policy->cpuid.basic.lppp )
+            policy->cpuid.basic.lppp = 2;
+        else if ( !(policy->cpuid.basic.lppp & 0x80) )
+            policy->cpuid.basic.lppp *= 2;
+
+        switch ( policy->cpuid.x86_vendor )
+        {
+        case X86_VENDOR_INTEL:
+            for ( i = 0; (policy->cpuid.cache.subleaf[i].type &&
+                          i < ARRAY_SIZE(policy->cpuid.cache.raw)); ++i )
+            {
+                policy->cpuid.cache.subleaf[i].cores_per_package =
+                  (policy->cpuid.cache.subleaf[i].cores_per_package << 1) | 1;
+                policy->cpuid.cache.subleaf[i].threads_per_cache = 0;
+            }
+            break;
+
+        case X86_VENDOR_AMD:
+        case X86_VENDOR_HYGON:
+            /*
+             * Leaf 0x80000008 ECX[15:12] is ApicIdCoreSize.
+             * Leaf 0x80000008 ECX[7:0] is NumberOfCores (minus one).
+             * Update to reflect vLAPIC_ID = vCPU_ID * 2.  But avoid
+             * - overflow,
+             * - going out of sync with leaf 1 EBX[23:16],
+             * - incrementing ApicIdCoreSize when it's zero (which changes the
+             *   meaning of bits 7:0).
+             *
+             * UPDATE: In addition to avoiding overflow, some
+             * proprietary operating systems have trouble with
+             * apic_id_size values greater than 7.  Limit the value to
+             * 7 for now.
+             */
+            if ( policy->cpuid.extd.nc < 0x7f )
+            {
+                if ( policy->cpuid.extd.apic_id_size != 0 &&
+                     policy->cpuid.extd.apic_id_size < 0x7 )
+                    policy->cpuid.extd.apic_id_size++;
+
+                policy->cpuid.extd.nc = (policy->cpuid.extd.nc << 1) | 1;
+            }
+            break;
+        }
+    }
+}
-- 
2.34.1