Subject: [PATCH LINUX v4] xen: event channel arrays are xen_ulong_t and not unsigned long

From: [email-masked] (Konrad Rzeszutek Wilk)
Date: Tue, 19 Feb 2013 22:09:43 -0500

On Tue, Feb 19, 2013 at 09:07:27PM -0500, Konrad Rzeszutek Wilk wrote:
> On Tue, Feb 19, 2013 at 05:29:11PM +0000, Ian Campbell wrote:
> > On ARM we want these to be the same size on 32- and 64-bit.
> > 
> > This is an ABI change on ARM. X86 does not change.
> 
> Hehe. You didn't test this, did you :-)
> 
> It hangs bootup on X86.

Ah wait. The version that hangs was the first posted - I hadn't
tested this one yet. I will wait until later on Wednesday to do that.

> > 
> > Signed-off-by: Ian Campbell <[email-masked]>
> > Cc: Jan Beulich <[email-masked]>
> > Cc: Keir (Xen.org) <[email-masked]>
> > Cc: Tim Deegan <[email-masked]>
> > Cc: Stefano Stabellini <[email-masked]>
> > Cc: linux-arm-kernel at lists.infradead.org
> > Cc: xen-devel at lists.xen.org
> > Cc: Konrad Rzeszutek Wilk <[email-masked]>
> > ---
> > Changes since V3
> >   s/read_evtchn_pending_sel/xchg_xen_ulong/ in a comment.
> > Changes since V2
> >   Add comments about the correct bitops to use, and on the ordering/barrier
> >   requirements on xchg_xen_ulong.
> > Changes since V1
> >   use find_first_set not __ffs
> >   fix some more unsigned long -> xen_ulong_t
> >   use more generic xchg_xen_ulong instead of ...read_evtchn...
> > ---
> >  arch/arm/include/asm/xen/events.h |   22 +++++++
> >  arch/x86/include/asm/xen/events.h |    3 +
> >  drivers/xen/events.c              |  113 +++++++++++++++++++++----------------
> >  include/xen/interface/xen.h       |    8 +-
> >  4 files changed, 94 insertions(+), 52 deletions(-)
> > 
> > diff --git a/arch/arm/include/asm/xen/events.h b/arch/arm/include/asm/xen/events.h
> > index 94b4e90..5c27696 100644
> > --- a/arch/arm/include/asm/xen/events.h
> > +++ b/arch/arm/include/asm/xen/events.h
> > @@ -15,4 +15,26 @@ static inline int xen_irqs_disabled(struct pt_regs *regs)
> >  	return raw_irqs_disabled_flags(regs->ARM_cpsr);
> >  }
> >  
> > +/*
> > + * We cannot use xchg because it does not support 8-byte
> > + * values. However it is safe to use {ldr,dtd}exd directly because all
> > + * platforms which Xen can run on support those instructions.
> > + */
> > +static inline xen_ulong_t xchg_xen_ulong(xen_ulong_t *ptr, xen_ulong_t val)
> > +{
> > +	xen_ulong_t oldval;
> > +	unsigned int tmp;
> > +
> > +	wmb();
> > +	asm volatile("@ xchg_xen_ulong\n"
> > +		"1:     ldrexd  %0, %H0, [%3]\n"
> > +		"       strexd  %1, %2, %H2, [%3]\n"
> > +		"       teq     %1, #0\n"
> > +		"       bne     1b"
> > +		: "=&r" (oldval), "=&r" (tmp)
> > +		: "r" (val), "r" (ptr)
> > +		: "memory", "cc");
> > +	return oldval;
> > +}
> > +
> >  #endif /* _ASM_ARM_XEN_EVENTS_H */
> > diff --git a/arch/x86/include/asm/xen/events.h b/arch/x86/include/asm/xen/events.h
> > index cc146d5..ca842f2 100644
> > --- a/arch/x86/include/asm/xen/events.h
> > +++ b/arch/x86/include/asm/xen/events.h
> > @@ -16,4 +16,7 @@ static inline int xen_irqs_disabled(struct pt_regs *regs)
> >  	return raw_irqs_disabled_flags(regs->flags);
> >  }
> >  
> > +/* No need for a barrier -- XCHG is a barrier on x86. */
> > +#define xchg_xen_ulong(ptr, val) xchg((ptr), (val))
> > +
> >  #endif /* _ASM_X86_XEN_EVENTS_H */
> > diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> > index 0be4df3..b8d84f5 100644
> > --- a/drivers/xen/events.c
> > +++ b/drivers/xen/events.c
> > @@ -80,6 +80,12 @@ enum xen_irq_type {
> >  };
> >  
> >  /*
> > + * Make a bitmask (i.e. unsigned long *) of a xen_ulong_t
> > + * array. Primarily to avoid long lines (hence the terse name).
> > + */
> > +#define BM(x) (unsigned long *)(x)
> > +
> > +/*
> >   * Packed IRQ information:
> >   * type - enum xen_irq_type
> >   * event channel - irq->event channel mapping
> > @@ -120,7 +126,14 @@ static unsigned long *pirq_eoi_map;
> >  #endif
> >  static bool (*pirq_needs_eoi)(unsigned irq);
> >  
> > -static DEFINE_PER_CPU(unsigned long [NR_EVENT_CHANNELS/BITS_PER_LONG],
> > +/*
> > + * Note sizeof(xen_ulong_t) can be more than sizeof(unsigned long). Be
> > + * careful to only use bitops which allow for this (e.g test_bit and
> > + * friends but not __ffs).
> > + */
> > +#define BITS_PER_EVTCHN_WORD (sizeof(xen_ulong_t)*8)
> > +
> > +static DEFINE_PER_CPU(xen_ulong_t [NR_EVENT_CHANNELS/BITS_PER_EVTCHN_WORD],
> >  		      cpu_evtchn_mask);
> >  
> >  /* Xen will never allocate port zero for any purpose. */
> > @@ -294,9 +307,9 @@ static bool pirq_needs_eoi_flag(unsigned irq)
> >  	return info->u.pirq.flags & PIRQ_NEEDS_EOI;
> >  }
> >  
> > -static inline unsigned long active_evtchns(unsigned int cpu,
> > -					   struct shared_info *sh,
> > -					   unsigned int idx)
> > +static inline xen_ulong_t active_evtchns(unsigned int cpu,
> > +					 struct shared_info *sh,
> > +					 unsigned int idx)
> >  {
> >  	return sh->evtchn_pending[idx] &
> >  		per_cpu(cpu_evtchn_mask, cpu)[idx] &
> > @@ -312,8 +325,8 @@ static void bind_evtchn_to_cpu(unsigned int chn, unsigned int cpu)
> >  	cpumask_copy(irq_to_desc(irq)->irq_data.affinity, cpumask_of(cpu));
> >  #endif
> >  
> > -	clear_bit(chn, per_cpu(cpu_evtchn_mask, cpu_from_irq(irq)));
> > -	set_bit(chn, per_cpu(cpu_evtchn_mask, cpu));
> > +	clear_bit(chn, BM(per_cpu(cpu_evtchn_mask, cpu_from_irq(irq))));
> > +	set_bit(chn, BM(per_cpu(cpu_evtchn_mask, cpu)));
> >  
> >  	info_for_irq(irq)->cpu = cpu;
> >  }
> > @@ -339,19 +352,19 @@ static void init_evtchn_cpu_bindings(void)
> >  static inline void clear_evtchn(int port)
> >  {
> >  	struct shared_info *s = HYPERVISOR_shared_info;
> > -	sync_clear_bit(port, &s->evtchn_pending[0]);
> > +	sync_clear_bit(port, BM(&s->evtchn_pending[0]));
> >  }
> >  
> >  static inline void set_evtchn(int port)
> >  {
> >  	struct shared_info *s = HYPERVISOR_shared_info;
> > -	sync_set_bit(port, &s->evtchn_pending[0]);
> > +	sync_set_bit(port, BM(&s->evtchn_pending[0]));
> >  }
> >  
> >  static inline int test_evtchn(int port)
> >  {
> >  	struct shared_info *s = HYPERVISOR_shared_info;
> > -	return sync_test_bit(port, &s->evtchn_pending[0]);
> > +	return sync_test_bit(port, BM(&s->evtchn_pending[0]));
> >  }
> >  
> >  
> > @@ -375,7 +388,7 @@ EXPORT_SYMBOL_GPL(notify_remote_via_irq);
> >  static void mask_evtchn(int port)
> >  {
> >  	struct shared_info *s = HYPERVISOR_shared_info;
> > -	sync_set_bit(port, &s->evtchn_mask[0]);
> > +	sync_set_bit(port, BM(&s->evtchn_mask[0]));
> >  }
> >  
> >  static void unmask_evtchn(int port)
> > @@ -389,7 +402,7 @@ static void unmask_evtchn(int port)
> >  	if (unlikely((cpu != cpu_from_evtchn(port))))
> >  		do_hypercall = 1;
> >  	else
> > -		evtchn_pending = sync_test_bit(port, &s->evtchn_pending[0]);
> > +		evtchn_pending = sync_test_bit(port, BM(&s->evtchn_pending[0]));
> >  
> >  	if (unlikely(evtchn_pending && xen_hvm_domain()))
> >  		do_hypercall = 1;
> > @@ -403,7 +416,7 @@ static void unmask_evtchn(int port)
> >  	} else {
> >  		struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
> >  
> > -		sync_clear_bit(port, &s->evtchn_mask[0]);
> > +		sync_clear_bit(port, BM(&s->evtchn_mask[0]));
> >  
> >  		/*
> >  		 * The following is basically the equivalent of
> > @@ -411,8 +424,8 @@ static void unmask_evtchn(int port)
> >  		 * the interrupt edge' if the channel is masked.
> >  		 */
> >  		if (evtchn_pending &&
> > -		    !sync_test_and_set_bit(port / BITS_PER_LONG,
> > -					   &vcpu_info->evtchn_pending_sel))
> > +		    !sync_test_and_set_bit(port / BITS_PER_EVTCHN_WORD,
> > +					   BM(&vcpu_info->evtchn_pending_sel)))
> >  			vcpu_info->evtchn_upcall_pending = 1;
> >  	}
> >  
> > @@ -1189,7 +1202,7 @@ irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
> >  {
> >  	struct shared_info *sh = HYPERVISOR_shared_info;
> >  	int cpu = smp_processor_id();
> > -	unsigned long *cpu_evtchn = per_cpu(cpu_evtchn_mask, cpu);
> > +	xen_ulong_t *cpu_evtchn = per_cpu(cpu_evtchn_mask, cpu);
> >  	int i;
> >  	unsigned long flags;
> >  	static DEFINE_SPINLOCK(debug_lock);
> > @@ -1205,7 +1218,7 @@ irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
> >  		pending = (get_irq_regs() && i == cpu)
> >  			? xen_irqs_disabled(get_irq_regs())
> >  			: v->evtchn_upcall_mask;
> > -		printk("%d: masked=%d pending=%d event_sel %0*lx\n  ", i,
> > +		printk("%d: masked=%d pending=%d event_sel %0*"PRI_xen_ulong"\n  ", i,
> >  		       pending, v->evtchn_upcall_pending,
> >  		       (int)(sizeof(v->evtchn_pending_sel)*2),
> >  		       v->evtchn_pending_sel);
> > @@ -1214,49 +1227,52 @@ irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
> >  
> >  	printk("\npending:\n   ");
> >  	for (i = ARRAY_SIZE(sh->evtchn_pending)-1; i >= 0; i--)
> > -		printk("%0*lx%s", (int)sizeof(sh->evtchn_pending[0])*2,
> > +		printk("%0*"PRI_xen_ulong"%s",
> > +		       (int)sizeof(sh->evtchn_pending[0])*2,
> >  		       sh->evtchn_pending[i],
> >  		       i % 8 == 0 ? "\n   " : " ");
> >  	printk("\nglobal mask:\n   ");
> >  	for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
> > -		printk("%0*lx%s",
> > +		printk("%0*"PRI_xen_ulong"%s",
> >  		       (int)(sizeof(sh->evtchn_mask[0])*2),
> >  		       sh->evtchn_mask[i],
> >  		       i % 8 == 0 ? "\n   " : " ");
> >  
> >  	printk("\nglobally unmasked:\n   ");
> >  	for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
> > -		printk("%0*lx%s", (int)(sizeof(sh->evtchn_mask[0])*2),
> > +		printk("%0*"PRI_xen_ulong"%s",
> > +		       (int)(sizeof(sh->evtchn_mask[0])*2),
> >  		       sh->evtchn_pending[i] & ~sh->evtchn_mask[i],
> >  		       i % 8 == 0 ? "\n   " : " ");
> >  
> >  	printk("\nlocal cpu%d mask:\n   ", cpu);
> > -	for (i = (NR_EVENT_CHANNELS/BITS_PER_LONG)-1; i >= 0; i--)
> > -		printk("%0*lx%s", (int)(sizeof(cpu_evtchn[0])*2),
> > +	for (i = (NR_EVENT_CHANNELS/BITS_PER_EVTCHN_WORD)-1; i >= 0; i--)
> > +		printk("%0*"PRI_xen_ulong"%s", (int)(sizeof(cpu_evtchn[0])*2),
> >  		       cpu_evtchn[i],
> >  		       i % 8 == 0 ? "\n   " : " ");
> >  
> >  	printk("\nlocally unmasked:\n   ");
> >  	for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--) {
> > -		unsigned long pending = sh->evtchn_pending[i]
> > +		xen_ulong_t pending = sh->evtchn_pending[i]
> >  			& ~sh->evtchn_mask[i]
> >  			& cpu_evtchn[i];
> > -		printk("%0*lx%s", (int)(sizeof(sh->evtchn_mask[0])*2),
> > +		printk("%0*"PRI_xen_ulong"%s",
> > +		       (int)(sizeof(sh->evtchn_mask[0])*2),
> >  		       pending, i % 8 == 0 ? "\n   " : " ");
> >  	}
> >  
> >  	printk("\npending list:\n");
> >  	for (i = 0; i < NR_EVENT_CHANNELS; i++) {
> > -		if (sync_test_bit(i, sh->evtchn_pending)) {
> > -			int word_idx = i / BITS_PER_LONG;
> > +		if (sync_test_bit(i, BM(sh->evtchn_pending))) {
> > +			int word_idx = i / BITS_PER_EVTCHN_WORD;
> >  			printk("  %d: event %d -> irq %d%s%s%s\n",
> >  			       cpu_from_evtchn(i), i,
> >  			       evtchn_to_irq[i],
> > -			       sync_test_bit(word_idx, &v->evtchn_pending_sel)
> > +			       sync_test_bit(word_idx, BM(&v->evtchn_pending_sel))
> >  					     ? "" : " l2-clear",
> > -			       !sync_test_bit(i, sh->evtchn_mask)
> > +			       !sync_test_bit(i, BM(sh->evtchn_mask))
> >  					     ? "" : " globally-masked",
> > -			       sync_test_bit(i, cpu_evtchn)
> > +			       sync_test_bit(i, BM(cpu_evtchn))
> >  					     ? "" : " locally-masked");
> >  		}
> >  	}
> > @@ -1273,7 +1289,7 @@ static DEFINE_PER_CPU(unsigned int, current_bit_idx);
> >  /*
> >   * Mask out the i least significant bits of w
> >   */
> > -#define MASK_LSBS(w, i) (w & ((~0UL) << i))
> > +#define MASK_LSBS(w, i) (w & ((~((xen_ulong_t)0UL)) << i))
> >  
> >  /*
> >   * Search the CPUs pending events bitmasks.  For each one found, map
> > @@ -1295,18 +1311,19 @@ static void __xen_evtchn_do_upcall(void)
> >  	unsigned count;
> >  
> >  	do {
> > -		unsigned long pending_words;
> > +		xen_ulong_t pending_words;
> >  
> >  		vcpu_info->evtchn_upcall_pending = 0;
> >  
> >  		if (__this_cpu_inc_return(xed_nesting_count) - 1)
> >  			goto out;
> >  
> > -#ifndef CONFIG_X86 /* No need for a barrier -- XCHG is a barrier on x86. */
> > -		/* Clear master flag /before/ clearing selector flag. */
> > -		wmb();
> > -#endif
> > -		pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0);
> > +		/*
> > +		 * Master flag must be /before/ clearing selector
> > +		 * flag. xchg_xen_ulong must contain an appropriate
> > +		 * barrier.
> > +		 */
> > +		pending_words = xchg_xen_ulong(&vcpu_info->evtchn_pending_sel, 0);
> >  
> >  		start_word_idx = __this_cpu_read(current_word_idx);
> >  		start_bit_idx = __this_cpu_read(current_bit_idx);
> > @@ -1314,8 +1331,8 @@ static void __xen_evtchn_do_upcall(void)
> >  		word_idx = start_word_idx;
> >  
> >  		for (i = 0; pending_words != 0; i++) {
> > -			unsigned long pending_bits;
> > -			unsigned long words;
> > +			xen_ulong_t pending_bits;
> > +			xen_ulong_t words;
> >  
> >  			words = MASK_LSBS(pending_words, word_idx);
> >  
> > @@ -1327,7 +1344,7 @@ static void __xen_evtchn_do_upcall(void)
> >  				bit_idx = 0;
> >  				continue;
> >  			}
> > -			word_idx = __ffs(words);
> > +			word_idx = find_first_bit(BM(&words), sizeof(words));
> >  
> >  			pending_bits = active_evtchns(cpu, s, word_idx);
> >  			bit_idx = 0; /* usually scan entire word from start */
> > @@ -1342,7 +1359,7 @@ static void __xen_evtchn_do_upcall(void)
> >  			}
> >  
> >  			do {
> > -				unsigned long bits;
> > +				xen_ulong_t bits;
> >  				int port, irq;
> >  				struct irq_desc *desc;
> >  
> > @@ -1352,10 +1369,10 @@ static void __xen_evtchn_do_upcall(void)
> >  				if (bits == 0)
> >  					break;
> >  
> > -				bit_idx = __ffs(bits);
> > +				bit_idx = find_first_bit(BM(&bits), sizeof(bits));
> >  
> >  				/* Process port. */
> > -				port = (word_idx * BITS_PER_LONG) + bit_idx;
> > +				port = (word_idx * BITS_PER_EVTCHN_WORD) + bit_idx;
> >  				irq = evtchn_to_irq[port];
> >  
> >  				if (irq != -1) {
> > @@ -1364,12 +1381,12 @@ static void __xen_evtchn_do_upcall(void)
> >  						generic_handle_irq_desc(irq, desc);
> >  				}
> >  
> > -				bit_idx = (bit_idx + 1) % BITS_PER_LONG;
> > +				bit_idx = (bit_idx + 1) % BITS_PER_EVTCHN_WORD;
> >  
> >  				/* Next caller starts at last processed + 1 */
> >  				__this_cpu_write(current_word_idx,
> >  						 bit_idx ? word_idx :
> > -						 (word_idx+1) % BITS_PER_LONG);
> > +						 (word_idx+1) % BITS_PER_EVTCHN_WORD);
> >  				__this_cpu_write(current_bit_idx, bit_idx);
> >  			} while (bit_idx != 0);
> >  
> > @@ -1377,7 +1394,7 @@ static void __xen_evtchn_do_upcall(void)
> >  			if ((word_idx != start_word_idx) || (i != 0))
> >  				pending_words &= ~(1UL << word_idx);
> >  
> > -			word_idx = (word_idx + 1) % BITS_PER_LONG;
> > +			word_idx = (word_idx + 1) % BITS_PER_EVTCHN_WORD;
> >  		}
> >  
> >  		BUG_ON(!irqs_disabled());
> > @@ -1487,8 +1504,8 @@ int resend_irq_on_evtchn(unsigned int irq)
> >  	if (!VALID_EVTCHN(evtchn))
> >  		return 1;
> >  
> > -	masked = sync_test_and_set_bit(evtchn, s->evtchn_mask);
> > -	sync_set_bit(evtchn, s->evtchn_pending);
> > +	masked = sync_test_and_set_bit(evtchn, BM(s->evtchn_mask));
> > +	sync_set_bit(evtchn, BM(s->evtchn_pending));
> >  	if (!masked)
> >  		unmask_evtchn(evtchn);
> >  
> > @@ -1536,8 +1553,8 @@ static int retrigger_dynirq(struct irq_data *data)
> >  	if (VALID_EVTCHN(evtchn)) {
> >  		int masked;
> >  
> > -		masked = sync_test_and_set_bit(evtchn, sh->evtchn_mask);
> > -		sync_set_bit(evtchn, sh->evtchn_pending);
> > +		masked = sync_test_and_set_bit(evtchn, BM(sh->evtchn_mask));
> > +		sync_set_bit(evtchn, BM(sh->evtchn_pending));
> >  		if (!masked)
> >  			unmask_evtchn(evtchn);
> >  		ret = 1;
> > diff --git a/include/xen/interface/xen.h b/include/xen/interface/xen.h
> > index 5d6c272..a9075df 100644
> > --- a/include/xen/interface/xen.h
> > +++ b/include/xen/interface/xen.h
> > @@ -285,7 +285,7 @@ DEFINE_GUEST_HANDLE_STRUCT(multicall_entry);
> >   * Event channel endpoints per domain:
> >   *  1024 if a long is 32 bits; 4096 if a long is 64 bits.
> >   */
> > -#define NR_EVENT_CHANNELS (sizeof(unsigned long) * sizeof(unsigned long) * 64)
> > +#define NR_EVENT_CHANNELS (sizeof(xen_ulong_t) * sizeof(xen_ulong_t) * 64)
> >  
> >  struct vcpu_time_info {
> >  	/*
> > @@ -341,7 +341,7 @@ struct vcpu_info {
> >  	 */
> >  	uint8_t evtchn_upcall_pending;
> >  	uint8_t evtchn_upcall_mask;
> > -	unsigned long evtchn_pending_sel;
> > +	xen_ulong_t evtchn_pending_sel;
> >  	struct arch_vcpu_info arch;
> >  	struct pvclock_vcpu_time_info time;
> >  }; /* 64 bytes (x86) */
> > @@ -384,8 +384,8 @@ struct shared_info {
> >  	 * per-vcpu selector word to be set. Each bit in the selector covers a
> >  	 * 'C long' in the PENDING bitfield array.
> >  	 */
> > -	unsigned long evtchn_pending[sizeof(unsigned long) * 8];
> > -	unsigned long evtchn_mask[sizeof(unsigned long) * 8];
> > +	xen_ulong_t evtchn_pending[sizeof(xen_ulong_t) * 8];
> > +	xen_ulong_t evtchn_mask[sizeof(xen_ulong_t) * 8];
> >  
> >  	/*
> >  	 * Wallclock time: updated only by control software. Guests should base
> > -- 
> > 1.7.2.5
> >