Re: [patch 20/26] Xen-paravirt_ops: Core Xen implementation

[Chris Wright]

* Ingo Molnar (mingo@xxxxxxx) wrote:
> * Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
> 
> > Core Xen Implementation
> > 
> > This patch is a rollup of all the core pieces of the Xen 
> > implementation, including booting, memory management, interrupts, time 
> > and so on.
> 
> > --- a/arch/i386/kernel/head.S
> > +++ b/arch/i386/kernel/head.S
> > @@ -535,6 +535,10 @@ unhandled_paravirt:
> >  	ud2
> >  #endif
> >  
> > +#ifdef CONFIG_XEN
> > +#include "../xen/xen-head.S"
> > +#endif
> 
> i'd suggest to remove the #ifdef and push it into xen-head.S.

That's been fixed, the two are built as seperate objects now.

> > @@ -437,9 +437,9 @@ static unsigned long native_store_tr(voi
> >  
> >  static void native_load_tls(struct thread_struct *t, unsigned int cpu)
> >  {
> > -#define C(i) get_cpu_gdt_table(cpu)[GDT_ENTRY_TLS_MIN + i] = t->tls_array[i]
> > -	C(0); C(1); C(2);
> > -#undef C
> > +	get_cpu_gdt_table(cpu)[GDT_ENTRY_TLS_MIN + 0] = t->tls_array[0];
> > +	get_cpu_gdt_table(cpu)[GDT_ENTRY_TLS_MIN + 1] = t->tls_array[1];
> > +	get_cpu_gdt_table(cpu)[GDT_ENTRY_TLS_MIN + 2] = t->tls_array[2];
> >  }
> 
> this is a cleanup unrelated to the purpose of the patch.

Sure, will split out.

> > +static void xen_safe_halt(void)
> > +{
> > +	stop_hz_timer();
> > +	/* Blocking includes an implicit local_irq_enable(). */
> > +	if (HYPERVISOR_sched_op(SCHEDOP_block, 0) != 0)
> > +		BUG();
> > +	start_hz_timer();
> > +}
> 
> change this to tick_nohz_stop_sched_tick()/restart_sched_tick() instead.

I don't think we want to do that.  It's dropped now with proper NO_HZ
support, as the core does that for us.

> > +static void xen_halt(void)
> > +{
> > +#if 0
> > +	if (irqs_disabled())
> > +		HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
> > +#endif
> 
> hm?

That's already been fixed.

> > +		op->arg1.linear_addr = arbitrary_virt_to_machine((unsigned long)addr).maddr;
> 
> 80+ chars line. (there are more instances of this throughout the patch)
> 
> > +	for (va = dtr->address, f = 0;
> > +	     va < dtr->address + size;
> > +	     va += PAGE_SIZE, f++) {
> > +		frames[f] = virt_to_mfn(va);
> > +		make_lowmem_page_readonly((void *)va);
> > +	}
> 
> coding style.
> 
> > +	/* This is used very early, so we can't rely on per-cpu data
> > +	   being set up, so no multicalls */
> 
> comment coding style. (there are instances of this throughout the patch)
> 
> > +	spin_lock(&lock);
> > +	for(in = out = 0; in < count; in++) {
> 
> missing whitespace.
> 
> > +		if (HYPERVISOR_update_descriptor(virt_to_machine(dt + entry*8).maddr,
> 
> 80+ chars.

cleaning those

> > +static void xen_set_iopl_mask(unsigned mask)
> > +{
> > +#if 0
> > +	struct physdev_set_iopl set_iopl;
> > +
> > +	/* Force the change at ring 0. */
> > +	set_iopl.iopl = (mask == 0) ? 1 : (mask >> 12) & 3;
> > +	HYPERVISOR_physdev_op(PHYSDEVOP_set_iopl, &set_iopl);
> > +#endif
> 
> hm?
> 
> > +	}
> > +
> > +	write_pda(xen.cr3, cr3);
> > +
> > +
> > +	{
> 
> unnecessary newline.

dropped

> > +static struct irq_chip xen_dynamic_chip __read_mostly = {
> > +	.name		= "xen-virq",
> > +	.mask		= disable_dynirq,
> > +	.unmask		= enable_dynirq,
> > +	.ack		= ack_dynirq,
> > +	.set_affinity	= set_affinity_irq,
> > +	.retrigger	= retrigger_dynirq,
> > +};
> 
> nicely done! :-)
> 
> > +void xen_set_pte(pte_t *ptep, pte_t pte)
> > +{
> > +#if 1
> > +	struct mmu_update u;
> > +
> > +	u.ptr = virt_to_machine(ptep).maddr;
> > +	u.val = pte_val_ma(pte);
> > +	if (HYPERVISOR_mmu_update(&u, 1, NULL, DOMID_SELF) < 0)
> > +		BUG();
> > +#else
> > +	ptep->pte_high = pte.pte_high;
> > +	smp_wmb();
> > +	ptep->pte_low = pte.pte_low;
> > +#endif
> 
> hm?

that's already been fixed

> > +	pgd = swapper_pg_dir + pgd_index(vaddr);
> > +	if (pgd_none(*pgd)) {
> > +		BUG();
> > +		return;
> 
> hm?
that's already been fixed

> > +void xen_pte_clear(struct mm_struct *mm, unsigned long addr,pte_t *ptep)
> > +{
> > +#if 1
> > +	ptep->pte_low = 0;
> > +	smp_wmb();
> > +	ptep->pte_high = 0;
> > +#else
> > +	set_64bit((u64 *)ptep, 0);
> > +#endif
> 
> hm?

that's already been fixed

> > +unsigned long xen_pmd_val(pmd_t pmd)
> > +{
> > +	BUG();
> > +	return 0;
> > +}
> 
> make it noret.

It's actually used now, so it's not noret-able (if that's a word ;-)
> 
> > +pmd_t xen_make_pmd(unsigned long pmd)
> > +{
> > +	BUG();
> > +	return __pmd(0);
> > +}
> 
> ditto.

ditto

> > +static void xen_timer_interrupt_hook(void)
> > +{
> 
> > +				runstate->time[RUNSTATE_offline] -
> > +				__get_cpu_var(processed_stolen_time);
> 
> NACK for now, for the reasons outlined in the 'stolen time' thread. 
> Stolen time accounting is a concept only related to the scheduler tick, 
> it's not a concept that should leak into normal timer interrupt 
> concepts.

As Jeremey mentioned in that thread, it's just used as a place
to tigger the caluculations periodically.

> > +	/* System-wide jiffy work. */
> > +	ticks = 0;
> > +	while(delta > NS_PER_TICK) {
> > +		delta -= NS_PER_TICK;
> > +		processed_system_time += NS_PER_TICK;
> > +		ticks++;
> > +	}
> > +	do_timer(ticks);
> 
> that should be updated to clockevents. (i suspect it already is?)

Yes it is.

> > +
> > +#if 0
> > +	if (unlikely((mfn >> machine_to_phys_order) != 0))
> > +		return max_mapnr;
> > +#endif
> 
> hm?

Good point, I don't recall the condition where that would get
triggered.

thanks,
-chris
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