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: Jeremy Fitzhardinge <jeremy@xensource.com> Signed-off-by: Chris Wright <chrisw@sous-sol.org>
This commit is contained in:
Jeremy Fitzhardinge
Jeremy Fitzhardinge
parent
f87e4cac4f
commit
f120f13ea0
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@ -4,7 +4,7 @@
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config XEN
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bool "Enable support for Xen hypervisor"
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depends on PARAVIRT && X86_CMPXCHG && X86_TSC && !(PREEMPT || NEED_MULTIPLE_NODES)
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depends on PARAVIRT && X86_CMPXCHG && X86_TSC && !NEED_MULTIPLE_NODES
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help
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This is the Linux Xen port. Enabling this will allow the
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kernel to boot in a paravirtualized environment under the
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@ -15,6 +15,7 @@
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#include <linux/init.h>
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#include <linux/smp.h>
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#include <linux/preempt.h>
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#include <linux/hardirq.h>
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#include <linux/percpu.h>
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#include <linux/delay.h>
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#include <linux/start_kernel.h>
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@ -108,11 +109,10 @@ static unsigned long xen_save_fl(void)
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struct vcpu_info *vcpu;
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unsigned long flags;
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preempt_disable();
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vcpu = x86_read_percpu(xen_vcpu);
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/* flag has opposite sense of mask */
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flags = !vcpu->evtchn_upcall_mask;
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preempt_enable();
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/* convert to IF type flag
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-0 -> 0x00000000
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@ -125,32 +125,35 @@ static void xen_restore_fl(unsigned long flags)
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{
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struct vcpu_info *vcpu;
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preempt_disable();
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/* convert from IF type flag */
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flags = !(flags & X86_EFLAGS_IF);
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/* There's a one instruction preempt window here. We need to
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make sure we're don't switch CPUs between getting the vcpu
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pointer and updating the mask. */
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preempt_disable();
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vcpu = x86_read_percpu(xen_vcpu);
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vcpu->evtchn_upcall_mask = flags;
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preempt_enable_no_resched();
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/* Doesn't matter if we get preempted here, because any
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pending event will get dealt with anyway. */
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if (flags == 0) {
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/* Unmask then check (avoid races). We're only protecting
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against updates by this CPU, so there's no need for
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anything stronger. */
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barrier();
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preempt_check_resched();
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barrier(); /* unmask then check (avoid races) */
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if (unlikely(vcpu->evtchn_upcall_pending))
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force_evtchn_callback();
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preempt_enable();
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} else
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preempt_enable_no_resched();
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}
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}
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static void xen_irq_disable(void)
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{
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struct vcpu_info *vcpu;
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/* There's a one instruction preempt window here. We need to
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make sure we're don't switch CPUs between getting the vcpu
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pointer and updating the mask. */
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preempt_disable();
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vcpu = x86_read_percpu(xen_vcpu);
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vcpu->evtchn_upcall_mask = 1;
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x86_read_percpu(xen_vcpu)->evtchn_upcall_mask = 1;
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preempt_enable_no_resched();
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}
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@ -158,18 +161,20 @@ static void xen_irq_enable(void)
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{
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struct vcpu_info *vcpu;
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/* There's a one instruction preempt window here. We need to
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make sure we're don't switch CPUs between getting the vcpu
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pointer and updating the mask. */
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preempt_disable();
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vcpu = x86_read_percpu(xen_vcpu);
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vcpu->evtchn_upcall_mask = 0;
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preempt_enable_no_resched();
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/* Unmask then check (avoid races). We're only protecting
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against updates by this CPU, so there's no need for
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anything stronger. */
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barrier();
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/* Doesn't matter if we get preempted here, because any
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pending event will get dealt with anyway. */
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barrier(); /* unmask then check (avoid races) */
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if (unlikely(vcpu->evtchn_upcall_pending))
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force_evtchn_callback();
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preempt_enable();
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}
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static void xen_safe_halt(void)
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@ -189,6 +194,8 @@ static void xen_halt(void)
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static void xen_set_lazy_mode(enum paravirt_lazy_mode mode)
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{
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BUG_ON(preemptible());
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switch (mode) {
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case PARAVIRT_LAZY_NONE:
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BUG_ON(x86_read_percpu(xen_lazy_mode) == PARAVIRT_LAZY_NONE);
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@ -293,9 +300,13 @@ static void xen_write_ldt_entry(struct desc_struct *dt, int entrynum,
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xmaddr_t mach_lp = virt_to_machine(lp);
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u64 entry = (u64)high << 32 | low;
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preempt_disable();
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xen_mc_flush();
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if (HYPERVISOR_update_descriptor(mach_lp.maddr, entry))
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BUG();
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preempt_enable();
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}
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static int cvt_gate_to_trap(int vector, u32 low, u32 high,
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@ -328,11 +339,13 @@ static DEFINE_PER_CPU(struct Xgt_desc_struct, idt_desc);
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static void xen_write_idt_entry(struct desc_struct *dt, int entrynum,
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u32 low, u32 high)
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{
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int cpu = smp_processor_id();
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unsigned long p = (unsigned long)&dt[entrynum];
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unsigned long start = per_cpu(idt_desc, cpu).address;
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unsigned long end = start + per_cpu(idt_desc, cpu).size + 1;
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unsigned long start, end;
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preempt_disable();
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start = __get_cpu_var(idt_desc).address;
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end = start + __get_cpu_var(idt_desc).size + 1;
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xen_mc_flush();
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@ -347,6 +360,8 @@ static void xen_write_idt_entry(struct desc_struct *dt, int entrynum,
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if (HYPERVISOR_set_trap_table(info))
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BUG();
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}
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preempt_enable();
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}
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static void xen_convert_trap_info(const struct Xgt_desc_struct *desc,
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@ -368,11 +383,9 @@ static void xen_convert_trap_info(const struct Xgt_desc_struct *desc,
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void xen_copy_trap_info(struct trap_info *traps)
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{
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const struct Xgt_desc_struct *desc = &get_cpu_var(idt_desc);
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const struct Xgt_desc_struct *desc = &__get_cpu_var(idt_desc);
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xen_convert_trap_info(desc, traps);
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put_cpu_var(idt_desc);
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}
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/* Load a new IDT into Xen. In principle this can be per-CPU, so we
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@ -382,12 +395,11 @@ static void xen_load_idt(const struct Xgt_desc_struct *desc)
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{
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static DEFINE_SPINLOCK(lock);
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static struct trap_info traps[257];
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int cpu = smp_processor_id();
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per_cpu(idt_desc, cpu) = *desc;
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spin_lock(&lock);
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__get_cpu_var(idt_desc) = *desc;
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xen_convert_trap_info(desc, traps);
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xen_mc_flush();
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@ -402,6 +414,8 @@ static void xen_load_idt(const struct Xgt_desc_struct *desc)
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static void xen_write_gdt_entry(struct desc_struct *dt, int entry,
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u32 low, u32 high)
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{
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preempt_disable();
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switch ((high >> 8) & 0xff) {
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case DESCTYPE_LDT:
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case DESCTYPE_TSS:
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@ -418,10 +432,12 @@ static void xen_write_gdt_entry(struct desc_struct *dt, int entry,
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}
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}
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preempt_enable();
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}
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static void xen_load_esp0(struct tss_struct *tss,
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struct thread_struct *thread)
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struct thread_struct *thread)
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{
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struct multicall_space mcs = xen_mc_entry(0);
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MULTI_stack_switch(mcs.mc, __KERNEL_DS, thread->esp0);
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@ -525,6 +541,8 @@ static unsigned long xen_read_cr3(void)
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static void xen_write_cr3(unsigned long cr3)
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{
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BUG_ON(preemptible());
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if (cr3 == x86_read_percpu(xen_cr3)) {
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/* just a simple tlb flush */
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xen_flush_tlb();
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@ -38,6 +38,7 @@
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*
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* Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
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*/
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#include <linux/sched.h>
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#include <linux/highmem.h>
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#include <linux/bug.h>
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#include <linux/sched.h>
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@ -531,5 +532,7 @@ void xen_exit_mmap(struct mm_struct *mm)
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drop_mm_ref(mm);
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put_cpu();
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spin_lock(&mm->page_table_lock);
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xen_pgd_unpin(mm->pgd);
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spin_unlock(&mm->page_table_lock);
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}
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@ -20,6 +20,7 @@
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* Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
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*/
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#include <linux/percpu.h>
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#include <linux/hardirq.h>
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#include <asm/xen/hypercall.h>
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@ -39,10 +40,12 @@ DEFINE_PER_CPU(unsigned long, xen_mc_irq_flags);
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void xen_mc_flush(void)
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{
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struct mc_buffer *b = &get_cpu_var(mc_buffer);
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struct mc_buffer *b = &__get_cpu_var(mc_buffer);
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int ret = 0;
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unsigned long flags;
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BUG_ON(preemptible());
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/* Disable interrupts in case someone comes in and queues
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something in the middle */
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local_irq_save(flags);
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@ -60,7 +63,6 @@ void xen_mc_flush(void)
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} else
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BUG_ON(b->argidx != 0);
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put_cpu_var(mc_buffer);
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local_irq_restore(flags);
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BUG_ON(ret);
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@ -68,10 +70,11 @@ void xen_mc_flush(void)
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struct multicall_space __xen_mc_entry(size_t args)
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{
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struct mc_buffer *b = &get_cpu_var(mc_buffer);
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struct mc_buffer *b = &__get_cpu_var(mc_buffer);
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struct multicall_space ret;
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unsigned argspace = (args + sizeof(u64) - 1) / sizeof(u64);
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BUG_ON(preemptible());
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BUG_ON(argspace > MC_ARGS);
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if (b->mcidx == MC_BATCH ||
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@ -83,7 +86,5 @@ struct multicall_space __xen_mc_entry(size_t args)
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ret.args = &b->args[b->argidx];
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b->argidx += argspace;
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put_cpu_var(mc_buffer);
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return ret;
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}
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@ -88,7 +88,7 @@ static void get_runstate_snapshot(struct vcpu_runstate_info *res)
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u64 state_time;
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struct vcpu_runstate_info *state;
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preempt_disable();
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BUG_ON(preemptible());
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state = &__get_cpu_var(runstate);
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@ -103,8 +103,6 @@ static void get_runstate_snapshot(struct vcpu_runstate_info *res)
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*res = *state;
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barrier();
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} while (get64(&state->state_entry_time) != state_time);
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preempt_enable();
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}
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static void setup_runstate_info(int cpu)
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@ -179,9 +177,19 @@ static void do_stolen_accounting(void)
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unsigned long long xen_sched_clock(void)
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{
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struct vcpu_runstate_info state;
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cycle_t now = xen_clocksource_read();
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cycle_t now;
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u64 ret;
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s64 offset;
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/*
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* Ideally sched_clock should be called on a per-cpu basis
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* anyway, so preempt should already be disabled, but that's
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* not current practice at the moment.
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*/
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preempt_disable();
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now = xen_clocksource_read();
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get_runstate_snapshot(&state);
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WARN_ON(state.state != RUNSTATE_running);
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@ -190,9 +198,13 @@ unsigned long long xen_sched_clock(void)
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if (offset < 0)
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offset = 0;
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return state.time[RUNSTATE_blocked] +
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ret = state.time[RUNSTATE_blocked] +
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state.time[RUNSTATE_running] +
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offset;
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preempt_enable();
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return ret;
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}
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