Patch "x86/cpu: Deal with broken firmware (VMWare/XEN)" has been added to the 4.8-stable tree

This is a note to let you know that I've just added the patch titled

x86/cpu: Deal with broken firmware (VMWare/XEN)

to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-cpu-deal-with-broken-firmware-vmware-xen.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Thomas Gleixner <[email protected]>
Date: Wed, 9 Nov 2016 16:35:51 +0100
Subject: x86/cpu: Deal with broken firmware (VMWare/XEN)

From: Thomas Gleixner <[email protected]>

commit d49597fd3bc7d9534de55e9256767f073be1b33a upstream.

Both ACPI and MP specifications require that the APIC id in the respective tables must be the same as the APIC id in CPUID.

The kernel retrieves the physical package id from the APIC id during the ACPI/MP table scan and builds the physical to logical package map. The physical package id which is used after a CPU comes up is retrieved from CPUID. So we rely on ACPI/MP tables and CPUID agreeing in that respect.

There exist VMware and XEN implementations which violate the spec. As a result the physical to logical package map, which relies on the ACPI/MP tables does not work on those systems, because the CPUID initialized physical package id does not match the firmware id. This causes system crashes and malfunction due to invalid package mappings.

The only way to cure this is to sanitize the physical package id after the CPUID enumeration and yell when the APIC ids are different. Fix up the initial APIC id, which is fine as it is only used printout purposes.

If the physical package IDs differ yell and use the package information from the ACPI/MP tables so the existing logical package map just works.

Chas provided the resulting dmesg output for his affected 4 virtual sockets, 1 core per socket VM:

[Firmware Bug]: CPU1: APIC id mismatch. Firmware: 1 CPUID: 2 [Firmware Bug]: CPU1: Using firmware package id 1 instead of 2
....

---
 arch/x86/kernel/cpu/common.c |   32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

@@ -979,6 +979,35 @@ static void x86_init_cache_qos(struct cp
 }
 
 /*
+ * The physical to logical package id mapping is initialized from the
+ * acpi/mptables information. Make sure that CPUID actually agrees with
+ * that.
+ */
+static void sanitize_package_id(struct cpuinfo_x86 *c)
+{
+#ifdef CONFIG_SMP
+	unsigned int pkg, apicid, cpu = smp_processor_id();
+
+	apicid = apic->cpu_present_to_apicid(cpu);
+	pkg = apicid >> boot_cpu_data.x86_coreid_bits;
+
+	if (apicid != c->initial_apicid) {
+		pr_err(FW_BUG "CPU%u: APIC id mismatch. Firmware: %x CPUID: %x\n",
+		       cpu, apicid, c->initial_apicid);
+		c->initial_apicid = apicid;
+	}
+	if (pkg != c->phys_proc_id) {
+		pr_err(FW_BUG "CPU%u: Using firmware package id %u instead of %u\n",
+		       cpu, pkg, c->phys_proc_id);
+		c->phys_proc_id = pkg;
+	}
+	c->logical_proc_id = topology_phys_to_logical_pkg(pkg);
+#else
+	c->logical_proc_id = 0;
+#endif
+}
+
+/*
  * This does the hard work of actually picking apart the CPU stuff...
  */
 static void identify_cpu(struct cpuinfo_x86 *c)

@@ -1103,8 +1132,7 @@ static void identify_cpu(struct cpuinfo_
 #ifdef CONFIG_NUMA
 	numa_add_cpu(smp_processor_id());
 #endif
-	/* The boot/hotplug time assigment got cleared, restore it */
-	c->logical_proc_id = topology_phys_to_logical_pkg(c->phys_proc_id);
+	sanitize_package_id(c);
 }
 
 /*

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/x86-cpu-amd-fix-cpu_llc_id-for-amd-fam17h-systems.patch queue-4.8/x86-cpu-deal-with-broken-firmware-vmware-xen.patch

Yes, please remove it from the stable queue for now. We'll have a fix ontop first and we'll submit both then as the check

	if (apicid != c->initial_apicid) {

fires on pretty much everything-AMD now.

Thanks.

Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

Now removed, thanks for letting me know.

greg k-h