Commit f120f13e authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Jeremy Fitzhardinge
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xen: Add support for preemption



Add Xen support for preemption.  This is mostly a cleanup of existing
preempt_enable/disable calls, or just comments to explain the current
usage.
Signed-off-by: default avatarJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: default avatarChris Wright <chrisw@sous-sol.org>
parent f87e4cac
......@@ -4,7 +4,7 @@
config XEN
bool "Enable support for Xen hypervisor"
depends on PARAVIRT && X86_CMPXCHG && X86_TSC && !(PREEMPT || NEED_MULTIPLE_NODES)
depends on PARAVIRT && X86_CMPXCHG && X86_TSC && !NEED_MULTIPLE_NODES
help
This is the Linux Xen port. Enabling this will allow the
kernel to boot in a paravirtualized environment under the
......
......@@ -15,6 +15,7 @@
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/preempt.h>
#include <linux/hardirq.h>
#include <linux/percpu.h>
#include <linux/delay.h>
#include <linux/start_kernel.h>
......@@ -108,11 +109,10 @@ static unsigned long xen_save_fl(void)
struct vcpu_info *vcpu;
unsigned long flags;
preempt_disable();
vcpu = x86_read_percpu(xen_vcpu);
/* flag has opposite sense of mask */
flags = !vcpu->evtchn_upcall_mask;
preempt_enable();
/* convert to IF type flag
-0 -> 0x00000000
......@@ -125,32 +125,35 @@ static void xen_restore_fl(unsigned long flags)
{
struct vcpu_info *vcpu;
preempt_disable();
/* convert from IF type flag */
flags = !(flags & X86_EFLAGS_IF);
/* There's a one instruction preempt window here. We need to
make sure we're don't switch CPUs between getting the vcpu
pointer and updating the mask. */
preempt_disable();
vcpu = x86_read_percpu(xen_vcpu);
vcpu->evtchn_upcall_mask = flags;
preempt_enable_no_resched();
if (flags == 0) {
/* Unmask then check (avoid races). We're only protecting
against updates by this CPU, so there's no need for
anything stronger. */
barrier();
/* Doesn't matter if we get preempted here, because any
pending event will get dealt with anyway. */
if (flags == 0) {
preempt_check_resched();
barrier(); /* unmask then check (avoid races) */
if (unlikely(vcpu->evtchn_upcall_pending))
force_evtchn_callback();
preempt_enable();
} else
preempt_enable_no_resched();
}
}
static void xen_irq_disable(void)
{
struct vcpu_info *vcpu;
/* There's a one instruction preempt window here. We need to
make sure we're don't switch CPUs between getting the vcpu
pointer and updating the mask. */
preempt_disable();
vcpu = x86_read_percpu(xen_vcpu);
vcpu->evtchn_upcall_mask = 1;
x86_read_percpu(xen_vcpu)->evtchn_upcall_mask = 1;
preempt_enable_no_resched();
}
......@@ -158,18 +161,20 @@ static void xen_irq_enable(void)
{
struct vcpu_info *vcpu;
/* There's a one instruction preempt window here. We need to
make sure we're don't switch CPUs between getting the vcpu
pointer and updating the mask. */
preempt_disable();
vcpu = x86_read_percpu(xen_vcpu);
vcpu->evtchn_upcall_mask = 0;
preempt_enable_no_resched();
/* Unmask then check (avoid races). We're only protecting
against updates by this CPU, so there's no need for
anything stronger. */
barrier();
/* Doesn't matter if we get preempted here, because any
pending event will get dealt with anyway. */
barrier(); /* unmask then check (avoid races) */
if (unlikely(vcpu->evtchn_upcall_pending))
force_evtchn_callback();
preempt_enable();
}
static void xen_safe_halt(void)
......@@ -189,6 +194,8 @@ static void xen_halt(void)
static void xen_set_lazy_mode(enum paravirt_lazy_mode mode)
{
BUG_ON(preemptible());
switch (mode) {
case PARAVIRT_LAZY_NONE:
BUG_ON(x86_read_percpu(xen_lazy_mode) == PARAVIRT_LAZY_NONE);
......@@ -293,9 +300,13 @@ static void xen_write_ldt_entry(struct desc_struct *dt, int entrynum,
xmaddr_t mach_lp = virt_to_machine(lp);
u64 entry = (u64)high << 32 | low;
preempt_disable();
xen_mc_flush();
if (HYPERVISOR_update_descriptor(mach_lp.maddr, entry))
BUG();
preempt_enable();
}
static int cvt_gate_to_trap(int vector, u32 low, u32 high,
......@@ -328,11 +339,13 @@ static DEFINE_PER_CPU(struct Xgt_desc_struct, idt_desc);
static void xen_write_idt_entry(struct desc_struct *dt, int entrynum,
u32 low, u32 high)
{
int cpu = smp_processor_id();
unsigned long p = (unsigned long)&dt[entrynum];
unsigned long start = per_cpu(idt_desc, cpu).address;
unsigned long end = start + per_cpu(idt_desc, cpu).size + 1;
unsigned long start, end;
preempt_disable();
start = __get_cpu_var(idt_desc).address;
end = start + __get_cpu_var(idt_desc).size + 1;
xen_mc_flush();
......@@ -347,6 +360,8 @@ static void xen_write_idt_entry(struct desc_struct *dt, int entrynum,
if (HYPERVISOR_set_trap_table(info))
BUG();
}
preempt_enable();
}
static void xen_convert_trap_info(const struct Xgt_desc_struct *desc,
......@@ -368,11 +383,9 @@ static void xen_convert_trap_info(const struct Xgt_desc_struct *desc,
void xen_copy_trap_info(struct trap_info *traps)
{
const struct Xgt_desc_struct *desc = &get_cpu_var(idt_desc);
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
......@@ -382,12 +395,11 @@ 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);
__get_cpu_var(idt_desc) = *desc;
xen_convert_trap_info(desc, traps);
xen_mc_flush();
......@@ -402,6 +414,8 @@ static void xen_load_idt(const struct Xgt_desc_struct *desc)
static void xen_write_gdt_entry(struct desc_struct *dt, int entry,
u32 low, u32 high)
{
preempt_disable();
switch ((high >> 8) & 0xff) {
case DESCTYPE_LDT:
case DESCTYPE_TSS:
......@@ -418,10 +432,12 @@ static void xen_write_gdt_entry(struct desc_struct *dt, int entry,
}
}
preempt_enable();
}
static void xen_load_esp0(struct tss_struct *tss,
struct thread_struct *thread)
struct thread_struct *thread)
{
struct multicall_space mcs = xen_mc_entry(0);
MULTI_stack_switch(mcs.mc, __KERNEL_DS, thread->esp0);
......@@ -525,6 +541,8 @@ static unsigned long xen_read_cr3(void)
static void xen_write_cr3(unsigned long cr3)
{
BUG_ON(preemptible());
if (cr3 == x86_read_percpu(xen_cr3)) {
/* just a simple tlb flush */
xen_flush_tlb();
......
......@@ -38,6 +38,7 @@
*
* Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
*/
#include <linux/sched.h>
#include <linux/highmem.h>
#include <linux/bug.h>
#include <linux/sched.h>
......@@ -531,5 +532,7 @@ void xen_exit_mmap(struct mm_struct *mm)
drop_mm_ref(mm);
put_cpu();
spin_lock(&mm->page_table_lock);
xen_pgd_unpin(mm->pgd);
spin_unlock(&mm->page_table_lock);
}
......@@ -20,6 +20,7 @@
* Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
*/
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <asm/xen/hypercall.h>
......@@ -39,10 +40,12 @@ DEFINE_PER_CPU(unsigned long, xen_mc_irq_flags);
void xen_mc_flush(void)
{
struct mc_buffer *b = &get_cpu_var(mc_buffer);
struct mc_buffer *b = &__get_cpu_var(mc_buffer);
int ret = 0;
unsigned long flags;
BUG_ON(preemptible());
/* Disable interrupts in case someone comes in and queues
something in the middle */
local_irq_save(flags);
......@@ -60,7 +63,6 @@ void xen_mc_flush(void)
} else
BUG_ON(b->argidx != 0);
put_cpu_var(mc_buffer);
local_irq_restore(flags);
BUG_ON(ret);
......@@ -68,10 +70,11 @@ void xen_mc_flush(void)
struct multicall_space __xen_mc_entry(size_t args)
{
struct mc_buffer *b = &get_cpu_var(mc_buffer);
struct mc_buffer *b = &__get_cpu_var(mc_buffer);
struct multicall_space ret;
unsigned argspace = (args + sizeof(u64) - 1) / sizeof(u64);
BUG_ON(preemptible());
BUG_ON(argspace > MC_ARGS);
if (b->mcidx == MC_BATCH ||
......@@ -83,7 +86,5 @@ struct multicall_space __xen_mc_entry(size_t args)
ret.args = &b->args[b->argidx];
b->argidx += argspace;
put_cpu_var(mc_buffer);
return ret;
}
......@@ -88,7 +88,7 @@ static void get_runstate_snapshot(struct vcpu_runstate_info *res)
u64 state_time;
struct vcpu_runstate_info *state;
preempt_disable();
BUG_ON(preemptible());
state = &__get_cpu_var(runstate);
......@@ -103,8 +103,6 @@ static void get_runstate_snapshot(struct vcpu_runstate_info *res)
*res = *state;
barrier();
} while (get64(&state->state_entry_time) != state_time);
preempt_enable();
}
static void setup_runstate_info(int cpu)
......@@ -179,9 +177,19 @@ static void do_stolen_accounting(void)
unsigned long long xen_sched_clock(void)
{
struct vcpu_runstate_info state;
cycle_t now = xen_clocksource_read();
cycle_t now;
u64 ret;
s64 offset;
/*
* Ideally sched_clock should be called on a per-cpu basis
* anyway, so preempt should already be disabled, but that's
* not current practice at the moment.
*/
preempt_disable();
now = xen_clocksource_read();
get_runstate_snapshot(&state);
WARN_ON(state.state != RUNSTATE_running);
......@@ -190,9 +198,13 @@ unsigned long long xen_sched_clock(void)
if (offset < 0)
offset = 0;
return state.time[RUNSTATE_blocked] +
ret = state.time[RUNSTATE_blocked] +
state.time[RUNSTATE_running] +
offset;
preempt_enable();
return ret;
}
......
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