Ian Campbell
2013-Feb-19 14:49 UTC
[PATCH LINUX] xen: event channel arrays are xen_ulong_t and not unsigned long
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.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Cc: Jan Beulich <JBeulich@suse.com>
Cc: Keir (Xen.org) <keir@xen.org>
Cc: Tim Deegan <tim@xen.org>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: xen-devel@lists.xen.org
---
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 | 103 ++++++++++++++++++++-----------------
include/xen/interface/xen.h | 8 ++--
4 files changed, 84 insertions(+), 52 deletions(-)
diff --git a/arch/arm/include/asm/xen/events.h
b/arch/arm/include/asm/xen/events.h
index 94b4e90..9bb5f50 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("@ read_evtchn_pending_sel\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..5618ca0 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 +126,9 @@ 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],
+#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 +302,9 @@ 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 +320,8 @@ 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 +347,19 @@ 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 +383,7 @@ 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 +397,7 @@ 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 +411,7 @@ 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 +419,8 @@ 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 +1197,7 @@ 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 +1213,7 @@ 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 +1222,52 @@ 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 +1284,7 @@ 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 +1306,14 @@ 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);
+ 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 +1321,8 @@ 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 +1334,7 @@ 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 +1349,7 @@ static void __xen_evtchn_do_upcall(void)
}
do {
- unsigned long bits;
+ xen_ulong_t bits;
int port, irq;
struct irq_desc *desc;
@@ -1352,10 +1359,10 @@ 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 +1371,12 @@ 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 +1384,7 @@ 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 +1494,8 @@ 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 +1543,8 @@ 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
Stefano Stabellini
2013-Feb-19 17:11 UTC
Re: [PATCH LINUX] xen: event channel arrays are xen_ulong_t and not unsigned long
On Tue, 19 Feb 2013, 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. > > Signed-off-by: Ian Campbell <ian.campbell@citrix.com> > Cc: Jan Beulich <JBeulich@suse.com> > Cc: Keir (Xen.org) <keir@xen.org> > Cc: Tim Deegan <tim@xen.org> > Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com> > Cc: linux-arm-kernel@lists.infradead.org > Cc: xen-devel@lists.xen.org > --- > 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 | 103 ++++++++++++++++++++----------------- > include/xen/interface/xen.h | 8 ++-- > 4 files changed, 84 insertions(+), 52 deletions(-)You might have to rebase this patch: it doesn''t apply on Linux 3.8.> diff --git a/arch/arm/include/asm/xen/events.h b/arch/arm/include/asm/xen/events.h > index 94b4e90..9bb5f50 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("@ read_evtchn_pending_sel\n"^ do we need this?> + "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 */[...]> @@ -1295,18 +1306,14 @@ 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(); > -#endifEven though I understand that moving wmb() into xchg_xen_ulong gets rid of an ugly ifndef, I am not sure whether it is a good thing from the code readability point of view. I''ll let Konrad decide on this one.> - pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0); > + 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 +1321,8 @@ 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 +1334,7 @@ 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 */is that because find_first_bit can actually cope with a bit number >32 and __ffs can''t? In that case it is worth adding a comment somewhere in this file, reminding people to only use bit operations that can handle size > unsigned long
Ian Campbell
2013-Feb-19 17:17 UTC
Re: [PATCH LINUX] xen: event channel arrays are xen_ulong_t and not unsigned long
On Tue, 2013-02-19 at 17:11 +0000, Stefano Stabellini wrote:> On Tue, 19 Feb 2013, 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. > > > > Signed-off-by: Ian Campbell <ian.campbell@citrix.com> > > Cc: Jan Beulich <JBeulich@suse.com> > > Cc: Keir (Xen.org) <keir@xen.org> > > Cc: Tim Deegan <tim@xen.org> > > Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com> > > Cc: linux-arm-kernel@lists.infradead.org > > Cc: xen-devel@lists.xen.org > > --- > > 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 | 103 ++++++++++++++++++++----------------- > > include/xen/interface/xen.h | 8 ++-- > > 4 files changed, 84 insertions(+), 52 deletions(-) > > You might have to rebase this patch: it doesn''t apply on Linux 3.8.Will do.> > > > diff --git a/arch/arm/include/asm/xen/events.h b/arch/arm/include/asm/xen/events.h > > index 94b4e90..9bb5f50 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("@ read_evtchn_pending_sel\n" > ^ do we need this?It means that the .s files (if you create them) and such are a bit more readable, it''s not that uncommon in the ARM inline assembly.> > + "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 */ > > [...] > > > @@ -1295,18 +1306,14 @@ 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 > > Even though I understand that moving wmb() into xchg_xen_ulong gets rid > of an ugly ifndef, I am not sure whether it is a good thing from the > code readability point of view. I''ll let Konrad decide on this one.I actually see this the other way -- this barrier is logically part of the exchange operation, implicitly on x86 and explicitly on ARM. I will add a comment here though, which I think is best of both.> > > > - pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0); > > + 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 +1321,8 @@ 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 +1334,7 @@ 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 */ > > is that because find_first_bit can actually cope with a bit number >> 32 and __ffs can''t?Yes.> In that case it is worth adding a comment somewhere in this file, > reminding people to only use bit operations that can handle size > > unsigned longWill do.
Tim Deegan
2013-Feb-19 17:26 UTC
Re: [PATCH LINUX] xen: event channel arrays are xen_ulong_t and not unsigned long
At 17:17 +0000 on 19 Feb (1361294248), Ian Campbell wrote:> On Tue, 2013-02-19 at 17:11 +0000, Stefano Stabellini wrote: > > On Tue, 19 Feb 2013, Ian Campbell wrote: > > > +/* > > > + * 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("@ read_evtchn_pending_sel\n" > > ^ do we need this? > > It means that the .s files (if you create them) and such are a bit more > readable, it''s not that uncommon in the ARM inline assembly.+1. s/read_evtchn_pending_sel/xchg_xen_ulong/ though. Tim.
Ian Campbell
2013-Feb-19 17:28 UTC
Re: [PATCH LINUX] xen: event channel arrays are xen_ulong_t and not unsigned long
On Tue, 2013-02-19 at 17:26 +0000, Tim Deegan wrote:> At 17:17 +0000 on 19 Feb (1361294248), Ian Campbell wrote: > > On Tue, 2013-02-19 at 17:11 +0000, Stefano Stabellini wrote: > > > On Tue, 19 Feb 2013, Ian Campbell wrote: > > > > +/* > > > > + * 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("@ read_evtchn_pending_sel\n" > > > ^ do we need this? > > > > It means that the .s files (if you create them) and such are a bit more > > readable, it''s not that uncommon in the ARM inline assembly. > > +1. s/read_evtchn_pending_sel/xchg_xen_ulong/ though.Damn, yes. I just sent v3 too :-( Ian.