Re: [PATCH] x86/smp: Fix __max_logical_packages value setup

Jiri Olsa
2016-08-12T12:26:39Z

On Thu, Aug 11, 2016 at 03:46:51PM +0200, Peter Zijlstra wrote:
> On Thu, Aug 11, 2016 at 03:05:21PM +0200, Jiri Olsa wrote:
> > hum, so we either need some acpi solution to get number of all
> > sockets or
>
> This.. So the problem here is that the BIOS completely screws us over.
>
> It wrecks the ACPI-ID table with that option to limit the number of CPUs
> exposed to the OS (note that it didn't need to do that, it could have
> enumerated them as empty, instead of not there at all) while keeping the
> CPUID of the CPUs as reporting they have many (12? was it) cores.
>
> This results in inconsistent state, and we're left with nothing useful.
>
> > fix the uncore code to initialize pmu boxes on cpu hotplug as well
>
> Can't.. it uses the boxes at STARTING time, and we can't do allocs
> there. Not can we alloc earlier, because we don't know max_packages is
> going to increase.

I still need to test this, but would this be something
like you proposed on irc?

thanks,
jirka

---
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 2a6e84a30a54..4296beb8fdd3 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -100,10 +100,11 @@ EXPORT_PER_CPU_SYMBOL(cpu_info);
/* Logical package management. We might want to allocate that dynamically */
static int *physical_to_logical_pkg __read_mostly;
static unsigned long *physical_package_map __read_mostly;;
-static unsigned long *logical_package_map __read_mostly;
static unsigned int max_physical_pkg_id __read_mostly;
unsigned int __max_logical_packages __read_mostly;
EXPORT_SYMBOL(__max_logical_packages);
+static unsigned int logical_packages __read_mostly;
+static bool logical_packages_frozen __read_mostly;

/* Maximum number of SMT threads on any online core */
int __max_smt_threads __read_mostly;
@@ -277,14 +278,14 @@ int topology_update_package_map(unsigned int apicid, unsigned int cpu)
if (test_and_set_bit(pkg, physical_package_map))
goto found;

- new = find_first_zero_bit(logical_package_map, __max_logical_packages);
- if (new >= __max_logical_packages) {
+ if (logical_packages_frozen) {
physical_to_logical_pkg[pkg] = -1;
- pr_warn("APIC(%x) Package %u exceeds logical package map\n",
+ pr_warn("APIC(%x) Package %u exceeds logical package max\n",
apicid, pkg);
return -ENOSPC;
}
- set_bit(new, logical_package_map);
+
+ new = logical_packages++;
pr_info("APIC(%x) Converting physical %u to logical package %u\n",
apicid, pkg, new);
physical_to_logical_pkg[pkg] = new;
@@ -341,6 +342,7 @@ static void __init smp_init_package_map(void)
}

__max_logical_packages = DIV_ROUND_UP(total_cpus, ncpus);
+ logical_packages = 0;

/*
* Possibly larger than what we need as the number of apic ids per
@@ -352,10 +354,6 @@ static void __init smp_init_package_map(void)
memset(physical_to_logical_pkg, 0xff, size);
size = BITS_TO_LONGS(max_physical_pkg_id) * sizeof(unsigned long);
physical_package_map = kzalloc(size, GFP_KERNEL);
- size = BITS_TO_LONGS(__max_logical_packages) * sizeof(unsigned long);
- logical_package_map = kzalloc(size, GFP_KERNEL);
-
- pr_info("Max logical packages: %u\n", __max_logical_packages);

for_each_present_cpu(cpu) {
unsigned int apicid = apic->cpu_present_to_apicid(cpu);
@@ -369,6 +367,15 @@ static void __init smp_init_package_map(void)
set_cpu_possible(cpu, false);
set_cpu_present(cpu, false);
}
+
+ if (logical_packages > __max_logical_packages) {
+ pr_warn("Detected more packages (%u), then computed by BIOS data (%u).\n",
+ logical_packages, __max_logical_packages);
+ logical_packages_frozen = true;
+ __max_logical_packages = logical_packages;
+ }
+
+ pr_info("Max logical packages: %u\n", __max_logical_packages);
}

void __init smp_store_boot_cpu_info(void)