[PATCH v2 8/8] xen/x86: Synthesise domain topologies

[Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>]

Expose sensible topologies in leaf 0xb. At the moment it synthesises non-HT
systems, in line with the previous code intent.

Signed-off-by: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
---
v2:
  * Zap the topology leaves of (pv/hvm)_(def/max)_policy rather than the host 
policy
---
 tools/libs/guest/xg_cpuid_x86.c | 62 +++++----------------------------
 xen/arch/x86/cpu-policy.c       |  9 +++--
 2 files changed, 15 insertions(+), 56 deletions(-)

diff --git a/tools/libs/guest/xg_cpuid_x86.c b/tools/libs/guest/xg_cpuid_x86.c
index 4453178100ad..8170769dbe43 100644
--- a/tools/libs/guest/xg_cpuid_x86.c
+++ b/tools/libs/guest/xg_cpuid_x86.c
@@ -584,7 +584,7 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t 
domid, bool restore,
     bool hvm;
     xc_domaininfo_t di;
     struct xc_cpu_policy *p = xc_cpu_policy_init();
-    unsigned int i, nr_leaves = ARRAY_SIZE(p->leaves), nr_msrs = 0;
+    unsigned int nr_leaves = ARRAY_SIZE(p->leaves), nr_msrs = 0;
     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);
@@ -727,59 +727,15 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t 
domid, bool restore,
     }
     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->policy.basic.htt = true;
-        p->policy.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->policy.basic.lppp )
-            p->policy.basic.lppp = 2;
-        else if ( !(p->policy.basic.lppp & 0x80) )
-            p->policy.basic.lppp *= 2;
-
-        switch ( p->policy.x86_vendor )
+        /* TODO: Expose the ability to choose a custom topology for HVM/PVH */
+        unsigned int threads_per_core = 1;
+        unsigned int cores_per_pkg = di.max_vcpu_id + 1;
+        rc = x86_topo_from_parts(&p->policy, threads_per_core, cores_per_pkg);
+        if ( rc )
         {
-        case X86_VENDOR_INTEL:
-            for ( i = 0; (p->policy.cache.subleaf[i].type &&
-                          i < ARRAY_SIZE(p->policy.cache.raw)); ++i )
-            {
-                p->policy.cache.subleaf[i].cores_per_package =
-                    (p->policy.cache.subleaf[i].cores_per_package << 1) | 1;
-                p->policy.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->policy.extd.nc < 0x7f )
-            {
-                if ( p->policy.extd.apic_id_size != 0 && 
p->policy.extd.apic_id_size < 0x7 )
-                    p->policy.extd.apic_id_size++;
-
-                p->policy.extd.nc = (p->policy.extd.nc << 1) | 1;
-            }
-            break;
+            ERROR("Failed to generate topology: t/c=%u c/p=%u",
+                  threads_per_core, cores_per_pkg);
+            goto out;
         }
     }
 
diff --git a/xen/arch/x86/cpu-policy.c b/xen/arch/x86/cpu-policy.c
index 4b6d96276399..0ad871732ba0 100644
--- a/xen/arch/x86/cpu-policy.c
+++ b/xen/arch/x86/cpu-policy.c
@@ -278,9 +278,6 @@ static void recalculate_misc(struct cpu_policy *p)
 
     p->basic.raw[0x8] = EMPTY_LEAF;
 
-    /* TODO: Rework topology logic. */
-    memset(p->topo.raw, 0, sizeof(p->topo.raw));
-
     p->basic.raw[0xc] = EMPTY_LEAF;
 
     p->extd.e1d &= ~CPUID_COMMON_1D_FEATURES;
@@ -621,6 +618,9 @@ static void __init calculate_pv_max_policy(void)
     recalculate_xstate(p);
 
     p->extd.raw[0xa] = EMPTY_LEAF; /* No SVM for PV guests. */
+
+    /* Wipe host topology. Toolstack is expected to synthesise a sensible one 
*/
+    memset(p->topo.raw, 0, sizeof(p->topo.raw));
 }
 
 static void __init calculate_pv_def_policy(void)
@@ -773,6 +773,9 @@ static void __init calculate_hvm_max_policy(void)
 
     /* It's always possible to emulate CPUID faulting for HVM guests */
     p->platform_info.cpuid_faulting = true;
+
+    /* Wipe host topology. Toolstack is expected to synthesise a sensible one 
*/
+    memset(p->topo.raw, 0, sizeof(p->topo.raw));
 }
 
 static void __init calculate_hvm_def_policy(void)
-- 
2.34.1