linux-brain/arch/x86/kernel/apic/bigsmp_32.c
Bandan Das bae3a8d330 x86/apic: Do not initialize LDR and DFR for bigsmp
Legacy apic init uses bigsmp for smp systems with 8 and more CPUs. The
bigsmp APIC implementation uses physical destination mode, but it
nevertheless initializes LDR and DFR. The LDR even ends up incorrectly with
multiple bit being set.

This does not cause a functional problem because LDR and DFR are ignored
when physical destination mode is active, but it triggered a problem on a
32-bit KVM guest which jumps into a kdump kernel.

The multiple bits set unearthed a bug in the KVM APIC implementation. The
code which creates the logical destination map for VCPUs ignores the
disabled state of the APIC and ends up overwriting an existing valid entry
and as a result, APIC calibration hangs in the guest during kdump
initialization.

Remove the bogus LDR/DFR initialization.

This is not intended to work around the KVM APIC bug. The LDR/DFR
ininitalization is wrong on its own.

The issue goes back into the pre git history. The fixes tag is the commit
in the bitkeeper import which introduced bigsmp support in 2003.

  git://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git

Fixes: db7b9e9f26b8 ("[PATCH] Clustered APIC setup for >8 CPU systems")
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20190826101513.5080-2-bsd@redhat.com
2019-08-26 20:00:56 +02:00

197 lines
4.4 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* APIC driver for "bigsmp" xAPIC machines with more than 8 virtual CPUs.
*
* Drives the local APIC in "clustered mode".
*/
#include <linux/threads.h>
#include <linux/cpumask.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/dmi.h>
#include <linux/smp.h>
#include <asm/apicdef.h>
#include <asm/fixmap.h>
#include <asm/mpspec.h>
#include <asm/apic.h>
#include <asm/ipi.h>
static unsigned bigsmp_get_apic_id(unsigned long x)
{
return (x >> 24) & 0xFF;
}
static int bigsmp_apic_id_registered(void)
{
return 1;
}
static bool bigsmp_check_apicid_used(physid_mask_t *map, int apicid)
{
return false;
}
static int bigsmp_early_logical_apicid(int cpu)
{
/* on bigsmp, logical apicid is the same as physical */
return early_per_cpu(x86_cpu_to_apicid, cpu);
}
/*
* bigsmp enables physical destination mode
* and doesn't use LDR and DFR
*/
static void bigsmp_init_apic_ldr(void)
{
}
static void bigsmp_setup_apic_routing(void)
{
printk(KERN_INFO
"Enabling APIC mode: Physflat. Using %d I/O APICs\n",
nr_ioapics);
}
static int bigsmp_cpu_present_to_apicid(int mps_cpu)
{
if (mps_cpu < nr_cpu_ids)
return (int) per_cpu(x86_bios_cpu_apicid, mps_cpu);
return BAD_APICID;
}
static void bigsmp_ioapic_phys_id_map(physid_mask_t *phys_map, physid_mask_t *retmap)
{
/* For clustered we don't have a good way to do this yet - hack */
physids_promote(0xFFL, retmap);
}
static int bigsmp_check_phys_apicid_present(int phys_apicid)
{
return 1;
}
static int bigsmp_phys_pkg_id(int cpuid_apic, int index_msb)
{
return cpuid_apic >> index_msb;
}
static void bigsmp_send_IPI_allbutself(int vector)
{
default_send_IPI_mask_allbutself_phys(cpu_online_mask, vector);
}
static void bigsmp_send_IPI_all(int vector)
{
default_send_IPI_mask_sequence_phys(cpu_online_mask, vector);
}
static int dmi_bigsmp; /* can be set by dmi scanners */
static int hp_ht_bigsmp(const struct dmi_system_id *d)
{
printk(KERN_NOTICE "%s detected: force use of apic=bigsmp\n", d->ident);
dmi_bigsmp = 1;
return 0;
}
static const struct dmi_system_id bigsmp_dmi_table[] = {
{ hp_ht_bigsmp, "HP ProLiant DL760 G2",
{ DMI_MATCH(DMI_BIOS_VENDOR, "HP"),
DMI_MATCH(DMI_BIOS_VERSION, "P44-"),
}
},
{ hp_ht_bigsmp, "HP ProLiant DL740",
{ DMI_MATCH(DMI_BIOS_VENDOR, "HP"),
DMI_MATCH(DMI_BIOS_VERSION, "P47-"),
}
},
{ } /* NULL entry stops DMI scanning */
};
static int probe_bigsmp(void)
{
if (def_to_bigsmp)
dmi_bigsmp = 1;
else
dmi_check_system(bigsmp_dmi_table);
return dmi_bigsmp;
}
static struct apic apic_bigsmp __ro_after_init = {
.name = "bigsmp",
.probe = probe_bigsmp,
.acpi_madt_oem_check = NULL,
.apic_id_valid = default_apic_id_valid,
.apic_id_registered = bigsmp_apic_id_registered,
.irq_delivery_mode = dest_Fixed,
/* phys delivery to target CPU: */
.irq_dest_mode = 0,
.disable_esr = 1,
.dest_logical = 0,
.check_apicid_used = bigsmp_check_apicid_used,
.init_apic_ldr = bigsmp_init_apic_ldr,
.ioapic_phys_id_map = bigsmp_ioapic_phys_id_map,
.setup_apic_routing = bigsmp_setup_apic_routing,
.cpu_present_to_apicid = bigsmp_cpu_present_to_apicid,
.apicid_to_cpu_present = physid_set_mask_of_physid,
.check_phys_apicid_present = bigsmp_check_phys_apicid_present,
.phys_pkg_id = bigsmp_phys_pkg_id,
.get_apic_id = bigsmp_get_apic_id,
.set_apic_id = NULL,
.calc_dest_apicid = apic_default_calc_apicid,
.send_IPI = default_send_IPI_single_phys,
.send_IPI_mask = default_send_IPI_mask_sequence_phys,
.send_IPI_mask_allbutself = NULL,
.send_IPI_allbutself = bigsmp_send_IPI_allbutself,
.send_IPI_all = bigsmp_send_IPI_all,
.send_IPI_self = default_send_IPI_self,
.inquire_remote_apic = default_inquire_remote_apic,
.read = native_apic_mem_read,
.write = native_apic_mem_write,
.eoi_write = native_apic_mem_write,
.icr_read = native_apic_icr_read,
.icr_write = native_apic_icr_write,
.wait_icr_idle = native_apic_wait_icr_idle,
.safe_wait_icr_idle = native_safe_apic_wait_icr_idle,
.x86_32_early_logical_apicid = bigsmp_early_logical_apicid,
};
void __init generic_bigsmp_probe(void)
{
unsigned int cpu;
if (!probe_bigsmp())
return;
apic = &apic_bigsmp;
for_each_possible_cpu(cpu) {
if (early_per_cpu(x86_cpu_to_logical_apicid,
cpu) == BAD_APICID)
continue;
early_per_cpu(x86_cpu_to_logical_apicid, cpu) =
bigsmp_early_logical_apicid(cpu);
}
pr_info("Overriding APIC driver with %s\n", apic_bigsmp.name);
}
apic_driver(apic_bigsmp);