Commit f87e4cac authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Jeremy Fitzhardinge
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xen: SMP guest support



This is a fairly straightforward Xen implementation of smp_ops.

Xen has its own IPI mechanisms, and has no dependency on any
APIC-based IPI.  The smp_ops hooks and the flush_tlb_others pv_op
allow a Xen guest to avoid all APIC code in arch/i386 (the only apic
operation is a single apic_read for the apic version number).

One subtle point which needs to be addressed is unpinning pagetables
when another cpu may have a lazy tlb reference to the pagetable. Xen
will not allow an in-use pagetable to be unpinned, so we must find any
other cpus with a reference to the pagetable and get them to shoot
down their references.
Signed-off-by: default avatarJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: default avatarChris Wright <chrisw@sous-sol.org>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Andi Kleen <ak@suse.de>
parent ab550288
......@@ -4,7 +4,7 @@
config XEN
bool "Enable support for Xen hypervisor"
depends on PARAVIRT && X86_CMPXCHG && X86_TSC && !(PREEMPT || SMP || NEED_MULTIPLE_NODES)
depends on PARAVIRT && X86_CMPXCHG && X86_TSC && !(PREEMPT || NEED_MULTIPLE_NODES)
help
This is the Linux Xen port. Enabling this will allow the
kernel to boot in a paravirtualized environment under the
......
obj-y := enlighten.o setup.o features.o multicalls.o mmu.o \
events.o time.o
obj-$(CONFIG_SMP) += smp.o
......@@ -24,6 +24,7 @@
#include <linux/mm.h>
#include <linux/page-flags.h>
#include <linux/highmem.h>
#include <linux/smp.h>
#include <xen/interface/xen.h>
#include <xen/interface/physdev.h>
......@@ -40,6 +41,7 @@
#include <asm/setup.h>
#include <asm/desc.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include "xen-ops.h"
#include "mmu.h"
......@@ -56,7 +58,7 @@ DEFINE_PER_CPU(unsigned long, xen_cr3);
struct start_info *xen_start_info;
EXPORT_SYMBOL_GPL(xen_start_info);
static void xen_vcpu_setup(int cpu)
void xen_vcpu_setup(int cpu)
{
per_cpu(xen_vcpu, cpu) = &HYPERVISOR_shared_info->vcpu_info[cpu];
}
......@@ -347,23 +349,14 @@ static void xen_write_idt_entry(struct desc_struct *dt, int entrynum,
}
}
/* Load a new IDT into Xen. In principle this can be per-CPU, so we
hold a spinlock to protect the static traps[] array (static because
it avoids allocation, and saves stack space). */
static void xen_load_idt(const struct Xgt_desc_struct *desc)
static void xen_convert_trap_info(const struct Xgt_desc_struct *desc,
struct trap_info *traps)
{
static DEFINE_SPINLOCK(lock);
static struct trap_info traps[257];
int cpu = smp_processor_id();
unsigned in, out, count;
per_cpu(idt_desc, cpu) = *desc;
count = (desc->size+1) / 8;
BUG_ON(count > 256);
spin_lock(&lock);
for (in = out = 0; in < count; in++) {
const u32 *entry = (u32 *)(desc->address + in * 8);
......@@ -371,6 +364,31 @@ static void xen_load_idt(const struct Xgt_desc_struct *desc)
out++;
}
traps[out].address = 0;
}
void xen_copy_trap_info(struct trap_info *traps)
{
const struct Xgt_desc_struct *desc = &get_cpu_var(idt_desc);
xen_convert_trap_info(desc, traps);
put_cpu_var(idt_desc);
}
/* Load a new IDT into Xen. In principle this can be per-CPU, so we
hold a spinlock to protect the static traps[] array (static because
it avoids allocation, and saves stack space). */
static void xen_load_idt(const struct Xgt_desc_struct *desc)
{
static DEFINE_SPINLOCK(lock);
static struct trap_info traps[257];
int cpu = smp_processor_id();
per_cpu(idt_desc, cpu) = *desc;
spin_lock(&lock);
xen_convert_trap_info(desc, traps);
xen_mc_flush();
if (HYPERVISOR_set_trap_table(traps))
......@@ -428,6 +446,12 @@ static unsigned long xen_apic_read(unsigned long reg)
{
return 0;
}
static void xen_apic_write(unsigned long reg, unsigned long val)
{
/* Warn to see if there's any stray references */
WARN_ON(1);
}
#endif
static void xen_flush_tlb(void)
......@@ -449,6 +473,40 @@ static void xen_flush_tlb_single(unsigned long addr)
BUG();
}
static void xen_flush_tlb_others(const cpumask_t *cpus, struct mm_struct *mm,
unsigned long va)
{
struct mmuext_op op;
cpumask_t cpumask = *cpus;
/*
* A couple of (to be removed) sanity checks:
*
* - current CPU must not be in mask
* - mask must exist :)
*/
BUG_ON(cpus_empty(cpumask));
BUG_ON(cpu_isset(smp_processor_id(), cpumask));
BUG_ON(!mm);
/* If a CPU which we ran on has gone down, OK. */
cpus_and(cpumask, cpumask, cpu_online_map);
if (cpus_empty(cpumask))
return;
if (va == TLB_FLUSH_ALL) {
op.cmd = MMUEXT_TLB_FLUSH_MULTI;
op.arg2.vcpumask = (void *)cpus;
} else {
op.cmd = MMUEXT_INVLPG_MULTI;
op.arg1.linear_addr = va;
op.arg2.vcpumask = (void *)cpus;
}
if (HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF))
BUG();
}
static unsigned long xen_read_cr2(void)
{
return x86_read_percpu(xen_vcpu)->arch.cr2;
......@@ -460,18 +518,6 @@ static void xen_write_cr4(unsigned long cr4)
native_write_cr4(cr4 & ~X86_CR4_TSD);
}
/*
* Page-directory addresses above 4GB do not fit into architectural %cr3.
* When accessing %cr3, or equivalent field in vcpu_guest_context, guests
* must use the following accessor macros to pack/unpack valid MFNs.
*
* Note that Xen is using the fact that the pagetable base is always
* page-aligned, and putting the 12 MSB of the address into the 12 LSB
* of cr3.
*/
#define xen_pfn_to_cr3(pfn) (((unsigned)(pfn) << 12) | ((unsigned)(pfn) >> 20))
#define xen_cr3_to_pfn(cr3) (((unsigned)(cr3) >> 12) | ((unsigned)(cr3) << 20))
static unsigned long xen_read_cr3(void)
{
return x86_read_percpu(xen_cr3);
......@@ -740,8 +786,8 @@ static const struct paravirt_ops xen_paravirt_ops __initdata = {
.io_delay = xen_io_delay,
#ifdef CONFIG_X86_LOCAL_APIC
.apic_write = paravirt_nop,
.apic_write_atomic = paravirt_nop,
.apic_write = xen_apic_write,
.apic_write_atomic = xen_apic_write,
.apic_read = xen_apic_read,
.setup_boot_clock = paravirt_nop,
.setup_secondary_clock = paravirt_nop,
......@@ -751,6 +797,7 @@ static const struct paravirt_ops xen_paravirt_ops __initdata = {
.flush_tlb_user = xen_flush_tlb,
.flush_tlb_kernel = xen_flush_tlb,
.flush_tlb_single = xen_flush_tlb_single,
.flush_tlb_others = xen_flush_tlb_others,
.pte_update = paravirt_nop,
.pte_update_defer = paravirt_nop,
......@@ -796,6 +843,19 @@ static const struct paravirt_ops xen_paravirt_ops __initdata = {
.set_lazy_mode = xen_set_lazy_mode,
};
#ifdef CONFIG_SMP
static const struct smp_ops xen_smp_ops __initdata = {
.smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu,
.smp_prepare_cpus = xen_smp_prepare_cpus,
.cpu_up = xen_cpu_up,
.smp_cpus_done = xen_smp_cpus_done,
.smp_send_stop = xen_smp_send_stop,
.smp_send_reschedule = xen_smp_send_reschedule,
.smp_call_function_mask = xen_smp_call_function_mask,
};
#endif /* CONFIG_SMP */
/* First C function to be called on Xen boot */
asmlinkage void __init xen_start_kernel(void)
{
......@@ -808,6 +868,9 @@ asmlinkage void __init xen_start_kernel(void)
/* Install Xen paravirt ops */
paravirt_ops = xen_paravirt_ops;
#ifdef CONFIG_SMP
smp_ops = xen_smp_ops;
#endif
xen_setup_features();
......
......@@ -47,6 +47,9 @@ static DEFINE_SPINLOCK(irq_mapping_update_lock);
/* IRQ <-> VIRQ mapping. */
static DEFINE_PER_CPU(int, virq_to_irq[NR_VIRQS]) = {[0 ... NR_VIRQS-1] = -1};
/* IRQ <-> IPI mapping */
static DEFINE_PER_CPU(int, ipi_to_irq[XEN_NR_IPIS]) = {[0 ... XEN_NR_IPIS-1] = -1};
/* Packed IRQ information: binding type, sub-type index, and event channel. */
struct packed_irq
{
......@@ -58,7 +61,13 @@ struct packed_irq
static struct packed_irq irq_info[NR_IRQS];
/* Binding types. */
enum { IRQT_UNBOUND, IRQT_PIRQ, IRQT_VIRQ, IRQT_IPI, IRQT_EVTCHN };
enum {
IRQT_UNBOUND,
IRQT_PIRQ,
IRQT_VIRQ,
IRQT_IPI,
IRQT_EVTCHN
};
/* Convenient shorthand for packed representation of an unbound IRQ. */
#define IRQ_UNBOUND mk_irq_info(IRQT_UNBOUND, 0, 0)
......@@ -261,6 +270,45 @@ static int bind_evtchn_to_irq(unsigned int evtchn)
return irq;
}
static int bind_ipi_to_irq(unsigned int ipi, unsigned int cpu)
{
struct evtchn_bind_ipi bind_ipi;
int evtchn, irq;
spin_lock(&irq_mapping_update_lock);
irq = per_cpu(ipi_to_irq, cpu)[ipi];
if (irq == -1) {
irq = find_unbound_irq();
if (irq < 0)
goto out;
dynamic_irq_init(irq);
set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,
handle_level_irq, "ipi");
bind_ipi.vcpu = cpu;
if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_ipi,
&bind_ipi) != 0)
BUG();
evtchn = bind_ipi.port;
evtchn_to_irq[evtchn] = irq;
irq_info[irq] = mk_irq_info(IRQT_IPI, ipi, evtchn);
per_cpu(ipi_to_irq, cpu)[ipi] = irq;
bind_evtchn_to_cpu(evtchn, cpu);
}
irq_bindcount[irq]++;
out:
spin_unlock(&irq_mapping_update_lock);
return irq;
}
static int bind_virq_to_irq(unsigned int virq, unsigned int cpu)
{
struct evtchn_bind_virq bind_virq;
......@@ -369,6 +417,28 @@ int bind_virq_to_irqhandler(unsigned int virq, unsigned int cpu,
}
EXPORT_SYMBOL_GPL(bind_virq_to_irqhandler);
int bind_ipi_to_irqhandler(enum ipi_vector ipi,
unsigned int cpu,
irq_handler_t handler,
unsigned long irqflags,
const char *devname,
void *dev_id)
{
int irq, retval;
irq = bind_ipi_to_irq(ipi, cpu);
if (irq < 0)
return irq;
retval = request_irq(irq, handler, irqflags, devname, dev_id);
if (retval != 0) {
unbind_from_irq(irq);
return retval;
}
return irq;
}
void unbind_from_irqhandler(unsigned int irq, void *dev_id)
{
free_irq(irq, dev_id);
......@@ -376,6 +446,14 @@ void unbind_from_irqhandler(unsigned int irq, void *dev_id)
}
EXPORT_SYMBOL_GPL(unbind_from_irqhandler);
void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector)
{
int irq = per_cpu(ipi_to_irq, cpu)[vector];
BUG_ON(irq < 0);
notify_remote_via_irq(irq);
}
/*
* Search the CPUs pending events bitmasks. For each one found, map
* the event number to an irq, and feed it into do_IRQ() for
......
......@@ -391,8 +391,12 @@ void xen_pgd_pin(pgd_t *pgd)
xen_mc_batch();
if (pgd_walk(pgd, pin_page, TASK_SIZE))
if (pgd_walk(pgd, pin_page, TASK_SIZE)) {
/* re-enable interrupts for kmap_flush_unused */
xen_mc_issue(0);
kmap_flush_unused();
xen_mc_batch();
}
mcs = __xen_mc_entry(sizeof(*op));
op = mcs.args;
......@@ -474,27 +478,58 @@ void xen_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
spin_unlock(&mm->page_table_lock);
}
void xen_exit_mmap(struct mm_struct *mm)
{
struct task_struct *tsk = current;
task_lock(tsk);
/*
* We aggressively remove defunct pgd from cr3. We execute unmap_vmas()
* *much* faster this way, as no tlb flushes means bigger wrpt batches.
*/
if (tsk->active_mm == mm) {
tsk->active_mm = &init_mm;
atomic_inc(&init_mm.mm_count);
#ifdef CONFIG_SMP
/* Another cpu may still have their %cr3 pointing at the pagetable, so
we need to repoint it somewhere else before we can unpin it. */
static void drop_other_mm_ref(void *info)
{
struct mm_struct *mm = info;
switch_mm(mm, &init_mm, tsk);
if (__get_cpu_var(cpu_tlbstate).active_mm == mm)
leave_mm(smp_processor_id());
}
atomic_dec(&mm->mm_count);
BUG_ON(atomic_read(&mm->mm_count) == 0);
static void drop_mm_ref(struct mm_struct *mm)
{
if (current->active_mm == mm) {
if (current->mm == mm)
load_cr3(swapper_pg_dir);
else
leave_mm(smp_processor_id());
}
task_unlock(tsk);
if (!cpus_empty(mm->cpu_vm_mask))
xen_smp_call_function_mask(mm->cpu_vm_mask, drop_other_mm_ref,
mm, 1);
}
#else
static void drop_mm_ref(struct mm_struct *mm)
{
if (current->active_mm == mm)
load_cr3(swapper_pg_dir);
}
#endif
/*
* While a process runs, Xen pins its pagetables, which means that the
* hypervisor forces it to be read-only, and it controls all updates
* to it. This means that all pagetable updates have to go via the
* hypervisor, which is moderately expensive.
*
* Since we're pulling the pagetable down, we switch to use init_mm,
* unpin old process pagetable and mark it all read-write, which
* allows further operations on it to be simple memory accesses.
*
* The only subtle point is that another CPU may be still using the
* pagetable because of lazy tlb flushing. This means we need need to
* switch all CPUs off this pagetable before we can unpin it.
*/
void xen_exit_mmap(struct mm_struct *mm)
{
get_cpu(); /* make sure we don't move around */
drop_mm_ref(mm);
put_cpu();
xen_pgd_unpin(mm->pgd);
}
......@@ -3,6 +3,19 @@
#include <linux/linkage.h>
#include <asm/page.h>
/*
* Page-directory addresses above 4GB do not fit into architectural %cr3.
* When accessing %cr3, or equivalent field in vcpu_guest_context, guests
* must use the following accessor macros to pack/unpack valid MFNs.
*
* Note that Xen is using the fact that the pagetable base is always
* page-aligned, and putting the 12 MSB of the address into the 12 LSB
* of cr3.
*/
#define xen_pfn_to_cr3(pfn) (((unsigned)(pfn) << 12) | ((unsigned)(pfn) >> 20))
#define xen_cr3_to_pfn(cr3) (((unsigned)(cr3) >> 12) | ((unsigned)(cr3) << 20))
void set_pte_mfn(unsigned long vaddr, unsigned long pfn, pgprot_t flags);
void xen_set_pte(pte_t *ptep, pte_t pteval);
......
......@@ -94,4 +94,9 @@ void __init xen_arch_setup(void)
COMMAND_LINE_SIZE : MAX_GUEST_CMDLINE);
pm_idle = xen_idle;
#ifdef CONFIG_SMP
/* fill cpus_possible with all available cpus */
xen_fill_possible_map();
#endif
}
/*
* Xen SMP support
*
* This file implements the Xen versions of smp_ops. SMP under Xen is
* very straightforward. Bringing a CPU up is simply a matter of
* loading its initial context and setting it running.
*
* IPIs are handled through the Xen event mechanism.
*
* Because virtual CPUs can be scheduled onto any real CPU, there's no
* useful topology information for the kernel to make use of. As a
* result, all CPUs are treated as if they're single-core and
* single-threaded.
*
* This does not handle HOTPLUG_CPU yet.
*/
#include <linux/sched.h>
#include <linux/err.h>
#include <linux/smp.h>
#include <asm/paravirt.h>
#include <asm/desc.h>
#include <asm/pgtable.h>
#include <asm/cpu.h>
#include <xen/interface/xen.h>
#include <xen/interface/vcpu.h>
#include <asm/xen/interface.h>
#include <asm/xen/hypercall.h>
#include <xen/page.h>
#include <xen/events.h>
#include "xen-ops.h"
#include "mmu.h"
static cpumask_t cpu_initialized_map;
static DEFINE_PER_CPU(int, resched_irq);
static DEFINE_PER_CPU(int, callfunc_irq);
/*
* Structure and data for smp_call_function(). This is designed to minimise
* static memory requirements. It also looks cleaner.
*/
static DEFINE_SPINLOCK(call_lock);
struct call_data_struct {
void (*func) (void *info);
void *info;
atomic_t started;
atomic_t finished;
int wait;
};
static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id);
static struct call_data_struct *call_data;
/*
* Reschedule call back. Nothing to do,
* all the work is done automatically when
* we return from the interrupt.
*/
static irqreturn_t xen_reschedule_interrupt(int irq, void *dev_id)
{
return IRQ_HANDLED;
}
static __cpuinit void cpu_bringup_and_idle(void)
{
int cpu = smp_processor_id();
cpu_init();
preempt_disable();
per_cpu(cpu_state, cpu) = CPU_ONLINE;
xen_setup_cpu_clockevents();
/* We can take interrupts now: we're officially "up". */
local_irq_enable();
wmb(); /* make sure everything is out */
cpu_idle();
}
static int xen_smp_intr_init(unsigned int cpu)
{
int rc;
const char *resched_name, *callfunc_name;
per_cpu(resched_irq, cpu) = per_cpu(callfunc_irq, cpu) = -1;
resched_name = kasprintf(GFP_KERNEL, "resched%d", cpu);
rc = bind_ipi_to_irqhandler(XEN_RESCHEDULE_VECTOR,
cpu,
xen_reschedule_interrupt,
IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
resched_name,
NULL);
if (rc < 0)
goto fail;
per_cpu(resched_irq, cpu) = rc;
callfunc_name = kasprintf(GFP_KERNEL, "callfunc%d", cpu);
rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_VECTOR,
cpu,
xen_call_function_interrupt,
IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
callfunc_name,
NULL);
if (rc < 0)
goto fail;
per_cpu(callfunc_irq, cpu) = rc;
return 0;
fail:
if (per_cpu(resched_irq, cpu) >= 0)
unbind_from_irqhandler(per_cpu(resched_irq, cpu), NULL);
if (per_cpu(callfunc_irq, cpu) >= 0)
unbind_from_irqhandler(per_cpu(callfunc_irq, cpu), NULL);
return rc;
}
void __init xen_fill_possible_map(void)
{
int i, rc;
for (i = 0; i < NR_CPUS; i++) {
rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
if (rc >= 0)
cpu_set(i, cpu_possible_map);
}
}
void __init xen_smp_prepare_boot_cpu(void)
{
int cpu;
BUG_ON(smp_processor_id() != 0);
native_smp_prepare_boot_cpu();
xen_vcpu_setup(0);
/* We've switched to the "real" per-cpu gdt, so make sure the
old memory can be recycled */
make_lowmem_page_readwrite(&per_cpu__gdt_page);
for (cpu = 0; cpu < NR_CPUS; cpu++) {
cpus_clear(cpu_sibling_map[cpu]);
cpus_clear(cpu_core_map[cpu]);
}
}
void __init xen_smp_prepare_cpus(unsigned int max_cpus)
{
unsigned cpu;
for (cpu = 0; cpu < NR_CPUS; cpu++) {
cpus_clear(cpu_sibling_map[cpu]);
cpus_clear(cpu_core_map[cpu]);
}
smp_store_cpu_info(0);
set_cpu_sibling_map(0);
if (xen_smp_intr_init(0))
BUG();
cpu_initialized_map = cpumask_of_cpu(0);
/* Restrict the possible_map according to max_cpus. */
while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
for (cpu = NR_CPUS-1; !cpu_isset(cpu, cpu_possible_map); cpu--)
continue;
cpu_clear(cpu, cpu_possible_map);
}
for_each_possible_cpu (cpu) {
struct task_struct *idle;