Work around regression in 4.15 in smpboot.c

Linux commit b4c0a7326f5d breaks PV domains since native_smp_cpus_done()
isn't called in that case. So __max_logical_packages is uninitialized
and breaks for example coretemp.

patches.xen/Revert-x86-smpboot-Do-not-use-smp_num_siblings-in-__.patch

@@ -0,0 +1,36 @@
+From 09c7513ec86caec1a1c304cf34d512011712f5c4 Mon Sep 17 00:00:00 2001
+From: Simon Gaiser <simon@invisiblethingslab.com>
+Date: Wed, 7 Feb 2018 18:30:53 +0100
+Subject: [PATCH 1/2] Revert "x86/smpboot: Do not use smp_num_siblings in
+ __max_logical_packages calculation"
+
+This reverts commit 947134d9b00f342415af7eddd42a5fce7262a1b9.
+---
+ arch/x86/kernel/smpboot.c | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
+index ed556d50d7ed..3dd6a6a5ffbc 100644
+--- a/arch/x86/kernel/smpboot.c
++++ b/arch/x86/kernel/smpboot.c
+@@ -106,7 +106,7 @@ EXPORT_SYMBOL(__max_logical_packages);
+ static unsigned int logical_packages __read_mostly;
+ 
+ /* Maximum number of SMT threads on any online core */
+-int __read_mostly __max_smt_threads = 1;
++int __max_smt_threads __read_mostly;
+ 
+ /* Flag to indicate if a complete sched domain rebuild is required */
+ bool x86_topology_update;
+@@ -1291,7 +1291,7 @@ void __init native_smp_cpus_done(unsigned int max_cpus)
+ 	 * Today neither Intel nor AMD support heterogenous systems so
+ 	 * extrapolate the boot cpu's data to all packages.
+ 	 */
+-	ncpus = cpu_data(0).booted_cores * topology_max_smt_threads();
++	ncpus = cpu_data(0).booted_cores * smp_num_siblings;
+ 	__max_logical_packages = DIV_ROUND_UP(nr_cpu_ids, ncpus);
+ 	pr_info("Max logical packages: %u\n", __max_logical_packages);
+ 
+-- 
+2.15.1
+

patches.xen/Revert-x86-smpboot-Fix-__max_logical_packages-estima.patch

@@ -0,0 +1,101 @@
+From 3379207879b4f1b6dff0cca0a713d5309e045c12 Mon Sep 17 00:00:00 2001
+From: Simon Gaiser <simon@invisiblethingslab.com>
+Date: Wed, 7 Feb 2018 18:31:03 +0100
+Subject: [PATCH 2/2] Revert "x86/smpboot: Fix __max_logical_packages estimate"
+
+This reverts commit b4c0a7326f5dc0ef7a64128b0ae7d081f4b2cbd1.
+---
+ arch/x86/kernel/smpboot.c | 55 ++++++++++++++++++++++++++++++++++++++---------
+ 1 file changed, 45 insertions(+), 10 deletions(-)
+
+diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
+index 3dd6a6a5ffbc..72b3eb321b49 100644
+--- a/arch/x86/kernel/smpboot.c
++++ b/arch/x86/kernel/smpboot.c
+@@ -301,6 +301,12 @@ int topology_update_package_map(unsigned int pkg, unsigned int cpu)
+ 	if (new >= 0)
+ 		goto found;
+ 
++	if (logical_packages >= __max_logical_packages) {
++		pr_warn("Package %u of CPU %u exceeds BIOS package data %u.\n",
++			logical_packages, cpu, __max_logical_packages);
++		return -ENOSPC;
++	}
++
+ 	new = logical_packages++;
+ 	if (new != pkg) {
+ 		pr_info("CPU %u Converting physical %u to logical package %u\n",
+@@ -311,6 +317,44 @@ int topology_update_package_map(unsigned int pkg, unsigned int cpu)
+ 	return 0;
+ }
+ 
++static void __init smp_init_package_map(struct cpuinfo_x86 *c, unsigned int cpu)
++{
++	unsigned int ncpus;
++
++	/*
++	 * Today neither Intel nor AMD support heterogenous systems. That
++	 * might change in the future....
++	 *
++	 * While ideally we'd want '* smp_num_siblings' in the below @ncpus
++	 * computation, this won't actually work since some Intel BIOSes
++	 * report inconsistent HT data when they disable HT.
++	 *
++	 * In particular, they reduce the APIC-IDs to only include the cores,
++	 * but leave the CPUID topology to say there are (2) siblings.
++	 * This means we don't know how many threads there will be until
++	 * after the APIC enumeration.
++	 *
++	 * By not including this we'll sometimes over-estimate the number of
++	 * logical packages by the amount of !present siblings, but this is
++	 * still better than MAX_LOCAL_APIC.
++	 *
++	 * We use total_cpus not nr_cpu_ids because nr_cpu_ids can be limited
++	 * on the command line leading to a similar issue as the HT disable
++	 * problem because the hyperthreads are usually enumerated after the
++	 * primary cores.
++	 */
++	ncpus = boot_cpu_data.x86_max_cores;
++	if (!ncpus) {
++		pr_warn("x86_max_cores == zero !?!?");
++		ncpus = 1;
++	}
++
++	__max_logical_packages = DIV_ROUND_UP(total_cpus, ncpus);
++	pr_info("Max logical packages: %u\n", __max_logical_packages);
++
++	topology_update_package_map(c->phys_proc_id, cpu);
++}
++
+ void __init smp_store_boot_cpu_info(void)
+ {
+ 	int id = 0; /* CPU 0 */
+@@ -318,7 +362,7 @@ void __init smp_store_boot_cpu_info(void)
+ 
+ 	*c = boot_cpu_data;
+ 	c->cpu_index = id;
+-	topology_update_package_map(c->phys_proc_id, id);
++	smp_init_package_map(c, id);
+ 	c->initialized = true;
+ }
+ 
+@@ -1284,16 +1328,7 @@ void __init native_smp_prepare_boot_cpu(void)
+ 
+ void __init native_smp_cpus_done(unsigned int max_cpus)
+ {
+-	int ncpus;
+-
+ 	pr_debug("Boot done\n");
+-	/*
+-	 * Today neither Intel nor AMD support heterogenous systems so
+-	 * extrapolate the boot cpu's data to all packages.
+-	 */
+-	ncpus = cpu_data(0).booted_cores * smp_num_siblings;
+-	__max_logical_packages = DIV_ROUND_UP(nr_cpu_ids, ncpus);
+-	pr_info("Max logical packages: %u\n", __max_logical_packages);
+ 
+ 	if (x86_has_numa_in_package)
+ 		set_sched_topology(x86_numa_in_package_topology);
+-- 
+2.15.1
+

series.conf

@@ -37,6 +37,10 @@ patches.xen/Revert-xen-optimize-xenbus-driver-for-multiple-concu.patch
 # Upstream patch for 4.15
 patches.xen/x86-xen-init-gs-very-early-to-avoid-page-faults-with.patch
 
+# Workaround for regression in 4.15 in smpboot.c
+patches.xen/Revert-x86-smpboot-Do-not-use-smp_num_siblings-in-__.patch
+patches.xen/Revert-x86-smpboot-Fix-__max_logical_packages-estima.patch
+
 # Hardware-specific fixes, backported from newer kernel and/or developers branches
 patches.backports/v2-2-2-Input-synaptics---Lenovo-X1-Carbon-5-should-use-SMBUS-RMI.patch
 patches.backports/Input-synaptics---add-Intertouch-support-on-X1-Carbon-6th-and-X280.patch