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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v8 for-xen-4.5 2/2] dpci: Replace tasklet with an softirq (v8)
On Mon, Oct 27, 2014 at 02:00:10PM -0400, Konrad Rzeszutek Wilk wrote:
> On Mon, Oct 27, 2014 at 05:36:03PM +0000, Andrew Cooper wrote:
> > On 27/10/14 17:01, Konrad Rzeszutek Wilk wrote:
> > > On Mon, Oct 27, 2014 at 11:24:31AM +0000, Jan Beulich wrote:
> > >>>>> On 27.10.14 at 12:09, <andrew.cooper3@xxxxxxxxxx> wrote:
> > >>> Can it ever be the case that we are waiting for a remote pcpu to run its
> > >>> softirq handler? If so, the time spent looping here could be up to 1
> > >>> scheduling timeslice in the worst case, and 30ms is a very long time to
> > >>> wait.
> > >> Good point - I think this can be the case. But there seems to be a
> > >> simple counter measure: The first time we get to this point, send an
> > >> event check IPI to the CPU in question (or in the worst case
> > >> broadcast one if the CPU can't be determined in a race free way).
> > > I can either do this using the wrapper:
> > >
> > > if ( pt_pirq_softirq_active(pirq_dpci) )
> > > {
> > > spin_unlock(&d->event_lock);
> > > if ( pirq_dpci->cpu >= 0 )
> > > {
> > > cpu_raise_softirq(pirq_dpci->cpu, HVM_DPCI_SOFTIRQ);
> > > pirq_dpci->cpu = -1;
> > > }
> > > cpu_relax();
> > > goto restart;
> > >
> > > Ought to do it (cpu_raise_softirq will exit out if
> > > the 'pirq_dpci->cpu == smp_processor_id()'). It also has some batching
> > > checks
> > > so that we won't do the IPI if we are in the middle of IPI-ing already
> > > an CPU.
> > >
> > > Or just write it out (and bypass some of the checks 'cpu_raise_softirq'
> > > has):
> > >
> > > if ( pt_pirq_softirq_active(pirq_dpci) )
> > > {
> > > spin_unlock(&d->event_lock);
> > > if ( pirq_dpci->cpu >= 0 && pirq_dpci->cpu != smp_processor_id() )
> > > {
> > > smp_send_event_check_cpu(pirq_dpci->cpu);
> > > pirq_dpci->cpu = -1;
> > > }
> > > cpu_relax();
> > > goto restart;
> > >
> > >
> > > Note:
> > >
> > > The 'cpu' is stashed whenever 'raise_softirq_for' has been called.
> > >
> >
> > You need to send at most 1 IPI, or you will be pointlessly spamming the
> > target pcpu. Therefore, a blind goto restart seems ill-advised.
>
> Right. That is what it does (it sets pirq_dpci->cpu to a negative value
> so that we don't try to spam the target).
> >
> > The second version doesn't necessarily set HVM_DPCI_SOFTIRQ pending,
>
> It does not have to as the target has already done so. That is because
> the ->cpu value is set in raise_softirq_for which also sets the
> HVM_DPIC_SOFTIRQ pending.
>
> > while the first version suffers a risk of the softirq being caught in a
> > batch.
>
> Correct.
> >
> > Furthermore, with mwait support, the IPI is elided completely, which is
> > completely wrong in this situation.
>
> Wait, where did that come from? If we use mwaits IPIs are ignored?
> Oh, you mean with the 'batching' support.
> >O
> > Therefore, I think you need to manually set the HVM_DPCI_SOFTIRQ bit,
> > then forcibly send the IPI.
>
> OK, so the second (smp_send_event_check_cpu). And the bit is already
> set - but I will add a comment explaining that.
This is what I came up with. Rather a simple change but I believe it
addresses your concerns.
Note that I could have also sprinkled 'pirq_dpci->cpu = -1' in
pt_pirq_softirq_reset (after the 'put_domain(d)') and in 'dpci_softirq'
(before clear_bit). But it is not needed - because we determine whether
to send an IPI based on the 'STATE_SCHED' bit and if that is unset
we don't care what is there.
Thought if it makes it more maintainable I can certainly add it there.
From 7ca4009e4613078ad603aef7af0cc65e6f8dd90f Mon Sep 17 00:00:00 2001
From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Date: Thu, 23 Oct 2014 20:41:24 -0400
Subject: [PATCH] dpci: Replace tasklet with an softirq (v10)
The existing tasklet mechanism has a single global
spinlock that is taken every-time the global list
is touched. And we use this lock quite a lot - when
we call do_tasklet_work which is called via an softirq
and from the idle loop. We take the lock on any
operation on the tasklet_list.
The problem we are facing is that there are quite a lot of
tasklets scheduled. The most common one that is invoked is
the one injecting the VIRQ_TIMER in the guest. Guests
are not insane and don't set the one-shot or periodic
clocks to be in sub 1ms intervals (causing said tasklet
to be scheduled for such small intervalls).
The problem appears when PCI passthrough devices are used
over many sockets and we have an mix of heavy-interrupt
guests and idle guests. The idle guests end up seeing
1/10 of its RUNNING timeslice eaten by the hypervisor
(and 40% steal time).
The mechanism by which we inject PCI interrupts is by
hvm_do_IRQ_dpci which schedules the hvm_dirq_assist
tasklet every time an interrupt is received.
The callchain is:
_asm_vmexit_handler
-> vmx_vmexit_handler
->vmx_do_extint
-> do_IRQ
-> __do_IRQ_guest
-> hvm_do_IRQ_dpci
tasklet_schedule(&dpci->dirq_tasklet);
[takes lock to put the tasklet on]
[later on the schedule_tail is invoked which is 'vmx_do_resume']
vmx_do_resume
-> vmx_asm_do_vmentry
-> call vmx_intr_assist
-> vmx_process_softirqs
-> do_softirq
[executes the tasklet function, takes the
lock again]
While on other CPUs they might be sitting in a idle loop
and invoked to deliver an VIRQ_TIMER, which also ends
up taking the lock twice: first to schedule the
v->arch.hvm_vcpu.assert_evtchn_irq_tasklet (accounted to
the guests' BLOCKED_state); then to execute it - which is
accounted for in the guest's RUNTIME_state.
The end result is that on a 8 socket machine with
PCI passthrough, where four sockets are busy with interrupts,
and the other sockets have idle guests - we end up with
the idle guests having around 40% steal time and 1/10
of its timeslice (3ms out of 30 ms) being tied up
taking the lock. The latency of the PCI interrupts delieved
to guest is also hindered.
With this patch the problem disappears completly.
That is removing the lock for the PCI passthrough use-case
(the 'hvm_dirq_assist' case) by not using tasklets at all.
The patch is simple - instead of scheduling an tasklet
we schedule our own softirq - HVM_DPCI_SOFTIRQ, which will
take care of running 'hvm_dirq_assist'. The information we need
on each CPU is which 'struct hvm_pirq_dpci' structure the
'hvm_dirq_assist' needs to run on. That is simple solved by
threading the 'struct hvm_pirq_dpci' through a linked list.
The rule of only running one 'hvm_dirq_assist' for only
one 'hvm_pirq_dpci' is also preserved by having
'schedule_dpci_for' ignore any subsequent calls for an domain
which has already been scheduled.
== Code details ==
Most of the code complexity comes from the '->dom' field
in the 'hvm_pirq_dpci' structure. We use it for ref-counting
and as such it MUST be valid as long as STATE_SCHED bit is
set. Whoever clears the STATE_SCHED bit does the ref-counting
and can also reset the '->dom' field.
To compound the complexity, there are multiple points where the
'hvm_pirq_dpci' structure is reset or re-used. Initially
(first time the domain uses the pirq), the 'hvm_pirq_dpci->dom'
field is set to NULL as it is allocated. On subsequent calls
in to 'pt_irq_create_bind' the ->dom is whatever it had last time.
As this is the initial call (which QEMU ends up calling when the
guest writes an vector value in the MSI field) we MUST set the
'->dom' to a the proper structure (otherwise we cannot do
proper ref-counting).
The mechanism to tear it down is more complex as there
are three ways it can be executed. To make it simpler
everything revolves around 'pt_pirq_softirq_active'. If it
returns -EAGAIN that means there is an outstanding softirq
that needs to finish running before we can continue tearing
down. With that in mind:
a) pci_clean_dpci_irq. This gets called when the guest is
being destroyed. We end up calling 'pt_pirq_softirq_active'
to see if it is OK to continue the destruction.
The scenarios in which the 'struct pirq' (and subsequently
the 'hvm_pirq_dpci') gets destroyed is when:
- guest did not use the pirq at all after setup.
- guest did use pirq, but decided to mask and left it in that
state.
- guest did use pirq, but crashed.
In all of those scenarios we end up calling
'pt_pirq_softirq_active' to check if the softirq is still
active. Read below on the 'pt_pirq_softirq_active' loop.
b) pt_irq_destroy_bind (guest disables the MSI). We double-check
that the softirq has run by piggy-backing on the existing
'pirq_cleanup_check' mechanism which calls 'pt_pirq_cleanup_check'.
We add the extra call to 'pt_pirq_softirq_active' in
'pt_pirq_cleanup_check'.
NOTE: Guests that use event channels unbind first the
event channel from PIRQs, so the 'pt_pirq_cleanup_check'
won't be called as 'event' is set to zero. In that case
we either clean it up via the a) or c) mechanism.
There is an extra scenario regardless of 'event' being
set or not: the guest did 'pt_irq_destroy_bind' while an
interrupt was triggered and softirq was scheduled (but had not
been run). It is OK to still run the softirq as
hvm_dirq_assist won't do anything (as the flags are
set to zero). However we will try to deschedule the
softirq if we can (by clearing the STATE_SCHED bit and us
doing the ref-counting).
c) pt_irq_create_bind (not a typo). The scenarios are:
- guest disables the MSI and then enables it
(rmmod and modprobe in a loop). We call 'pt_pirq_reset'
which checks to see if the softirq has been scheduled.
Imagine the 'b)' with interrupts in flight and c) getting
called in a loop.
We will spin up on 'pt_pirq_is_active' (at the start of the
'pt_irq_create_bind') with the event_lock spinlock dropped and
calling 'process_pending_softirqs'. hvm_dirq_assist will be executed
and then the softirq will clear 'state' which signals that that we
can re-use the 'hvm_pirq_dpci' structure.
- we hit once the error paths in 'pt_irq_create_bind' while
an interrupt was triggered and softirq was scheduled.
If the softirq is in STATE_RUN that means it is executing and we should
let it continue on. We can clear the '->dom' field as the softirq
has stashed it beforehand. If the softirq is STATE_SCHED and
we are successful in clearing it, we do the ref-counting and
clear the '->dom' field. Otherwise we let the softirq continue
on and the '->dom' field is left intact. The clearing of
the '->dom' is left to a), b) or again c) case.
Note that in both cases the 'flags' variable is cleared so
hvm_dirq_assist won't actually do anything.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Suggested-by: Jan Beulich <JBeulich@xxxxxxxx>
---
v2: On top of ref-cnts also have wait loop for the outstanding
'struct domain' that need to be processed.
v3: Add -ERETRY, fix up StyleGuide issues
v4: Clean it up mode, redo per_cpu, this_cpu logic
v5: Instead of threading struct domain, use hvm_pirq_dpci.
v6: Ditch the 'state' bit, expand description, simplify
softirq and teardown sequence.
v7: Flesh out the comments. Drop the use of domain refcounts
v8: Add two bits (STATE_[SCHED|RUN]) to allow refcounts.
v9: Use cmpxchg, ASSSERT, fix up comments per Jan.
v10: Fix up issues spotted by Jan and Andrew.
---
xen/arch/x86/domain.c | 4 +-
xen/drivers/passthrough/io.c | 266 +++++++++++++++++++++++++++++++++++++-----
xen/drivers/passthrough/pci.c | 31 +++--
xen/include/asm-x86/softirq.h | 3 +-
xen/include/xen/hvm/irq.h | 6 +-
xen/include/xen/pci.h | 2 +-
6 files changed, 269 insertions(+), 43 deletions(-)
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index ae0a344..73d01bb 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1965,7 +1965,9 @@ int domain_relinquish_resources(struct domain *d)
switch ( d->arch.relmem )
{
case RELMEM_not_started:
- pci_release_devices(d);
+ ret = pci_release_devices(d);
+ if ( ret )
+ return ret;
/* Tear down paging-assistance stuff. */
ret = paging_teardown(d);
diff --git a/xen/drivers/passthrough/io.c b/xen/drivers/passthrough/io.c
index dceb17e..66869e9 100644
--- a/xen/drivers/passthrough/io.c
+++ b/xen/drivers/passthrough/io.c
@@ -20,14 +20,125 @@
#include <xen/event.h>
#include <xen/iommu.h>
+#include <xen/cpu.h>
#include <xen/irq.h>
#include <asm/hvm/irq.h>
#include <asm/hvm/iommu.h>
#include <asm/hvm/support.h>
#include <xen/hvm/irq.h>
-#include <xen/tasklet.h>
-static void hvm_dirq_assist(unsigned long arg);
+static DEFINE_PER_CPU(struct list_head, dpci_list);
+
+/*
+ * These two bit states help to safely schedule, deschedule, and wait until
+ * the softirq has finished.
+ *
+ * The semantics behind these two bits is as follow:
+ * - STATE_SCHED - whoever modifies it has to ref-count the domain (->dom).
+ * - STATE_RUN - only softirq is allowed to set and clear it. If it has
+ * been set hvm_dirq_assist will RUN with a saved value of the
+ * 'struct domain' copied from 'pirq_dpci->dom' before STATE_RUN was set.
+ *
+ * The usual states are: STATE_SCHED(set) -> STATE_RUN(set) ->
+ * STATE_SCHED(unset) -> STATE_RUN(unset).
+ *
+ * However the states can also diverge such as: STATE_SCHED(set) ->
+ * STATE_SCHED(unset) -> STATE_RUN(set) -> STATE_RUN(unset). That means
+ * the 'hvm_dirq_assist' never run and that the softirq did not do any
+ * ref-counting.
+ */
+
+enum {
+ STATE_SCHED,
+ STATE_RUN
+};
+
+/*
+ * Should only be called from hvm_do_IRQ_dpci. We use the
+ * 'state' as a gate to thwart multiple interrupts being scheduled.
+ * The 'state' is cleared by 'softirq_dpci' when it has
+ * completed executing 'hvm_dirq_assist' or by 'pt_pirq_softirq_reset'
+ * if we want to try to unschedule the softirq before it runs.
+ *
+ */
+static void raise_softirq_for(struct hvm_pirq_dpci *pirq_dpci)
+{
+ unsigned long flags;
+ unsigned int cpu;
+
+ if ( test_and_set_bit(STATE_SCHED, &pirq_dpci->state) )
+ return;
+
+ cpu = smp_processor_id();
+ pirq_dpci->cpu = cpu;
+ get_knownalive_domain(pirq_dpci->dom);
+
+ local_irq_save(flags);
+ list_add_tail(&pirq_dpci->softirq_list, &per_cpu(dpci_list, cpu));
+ local_irq_restore(flags);
+
+ raise_softirq(HVM_DPCI_SOFTIRQ);
+}
+
+/*
+ * If we are racing with softirq_dpci (state is still set) we return
+ * true. Otherwise we return false.
+ *
+ * If it is false, it is the callers responsibility to make sure
+ * that the softirq (with the event_lock dropped) has ran. We need
+ * to flush out the outstanding 'dpci_softirq' (no more of them
+ * will be added for this pirq as the IRQ action handler has been
+ * reset in pt_irq_destroy_bind).
+ */
+bool_t pt_pirq_softirq_active(struct hvm_pirq_dpci *pirq_dpci)
+{
+ if ( pirq_dpci->state & ((1 << STATE_RUN) | (1 << STATE_SCHED)) )
+ return 1;
+
+ /*
+ * If in the future we would call 'raise_softirq_for' right away
+ * after 'pt_pirq_softirq_active' we MUST reset the list (otherwise it
+ * might have stale data).
+ */
+ return 0;
+}
+
+/*
+ * Reset the pirq_dpci->dom parameter to NULL.
+ *
+ * This function checks the different states to make sure it can do
+ * at the right time and if unschedules the softirq before it has
+ * run it also refcounts (which is what the softirq would have done).
+ */
+static void pt_pirq_softirq_reset(struct hvm_pirq_dpci *pirq_dpci)
+{
+ struct domain *d = pirq_dpci->dom;
+
+ ASSERT(spin_is_locked(&d->event_lock));
+
+ switch ( cmpxchg(&pirq_dpci->state, 1 << STATE_SCHED, 0) )
+ {
+ /*
+ * We are going to try to de-schedule the softirq before it goes in
+ * STATE_RUN. Whoever clears STATE_SCHED MUST refcount the 'dom'.
+ */
+ case (1 << STATE_SCHED):
+ put_domain(d);
+ /* fallthrough. */
+ /*
+ * The reason it is OK to reset 'dom' when STATE_RUN bit is set is
+ * due to a shortcut the 'dpci_softirq' implements. It stashes the
+ * a 'dom' in local variable before it sets STATE_RUN - and
+ * therefore will not dereference '->dom' which would crash.
+ */
+ case (1 << STATE_RUN):
+ case (1 << STATE_RUN) | (1 << STATE_SCHED):
+ pirq_dpci->dom = NULL;
+ break;
+ default:
+ break;
+ }
+}
bool_t pt_irq_need_timer(uint32_t flags)
{
@@ -40,7 +151,7 @@ static int pt_irq_guest_eoi(struct domain *d, struct
hvm_pirq_dpci *pirq_dpci,
if ( __test_and_clear_bit(_HVM_IRQ_DPCI_EOI_LATCH_SHIFT,
&pirq_dpci->flags) )
{
- pirq_dpci->masked = 0;
+ pirq_dpci->state = 0;
pirq_dpci->pending = 0;
pirq_guest_eoi(dpci_pirq(pirq_dpci));
}
@@ -101,6 +212,7 @@ int pt_irq_create_bind(
if ( pirq < 0 || pirq >= d->nr_pirqs )
return -EINVAL;
+ restart:
spin_lock(&d->event_lock);
hvm_irq_dpci = domain_get_irq_dpci(d);
@@ -127,7 +239,29 @@ int pt_irq_create_bind(
return -ENOMEM;
}
pirq_dpci = pirq_dpci(info);
-
+ /*
+ * A crude 'while' loop with us dropping the spinlock and giving
+ * the softirq_dpci a chance to run.
+ * We MUST check for this condition as the softirq could be scheduled
+ * and hasn't run yet. Note that this code replaced tasklet_kill which
+ * would have spun forever and would do the same thing (wait to flush out
+ * outstanding hvm_dirq_assist calls.
+ */
+ if ( pt_pirq_softirq_active(pirq_dpci) )
+ {
+ spin_unlock(&d->event_lock);
+ if ( pirq_dpci->cpu >= 0 && pirq_dpci->cpu != smp_processor_id() )
+ {
+ /*
+ * The 'raise_softirq_for' sets the CPU and raises the softirq bit
+ * so we do not need to set the target CPU's HVM_DPCI_SOFTIRQ.
+ */
+ smp_send_event_check_cpu(pirq_dpci->cpu);
+ pirq_dpci->cpu = -1;
+ }
+ cpu_relax();
+ goto restart;
+ }
switch ( pt_irq_bind->irq_type )
{
case PT_IRQ_TYPE_MSI:
@@ -165,8 +299,14 @@ int pt_irq_create_bind(
{
pirq_dpci->gmsi.gflags = 0;
pirq_dpci->gmsi.gvec = 0;
- pirq_dpci->dom = NULL;
pirq_dpci->flags = 0;
+ /*
+ * Between the 'pirq_guest_bind' and before 'pirq_guest_unbind'
+ * an interrupt can be scheduled. No more of them are going to
+ * be scheduled but we must deal with the one that is in the
+ * queue.
+ */
+ pt_pirq_softirq_reset(pirq_dpci);
pirq_cleanup_check(info, d);
spin_unlock(&d->event_lock);
return rc;
@@ -269,6 +409,10 @@ int pt_irq_create_bind(
{
if ( pt_irq_need_timer(pirq_dpci->flags) )
kill_timer(&pirq_dpci->timer);
+ /*
+ * There is no path for __do_IRQ to schedule softirq as
+ * IRQ_GUEST is not set. As such we can reset 'dom' right away.
+ */
pirq_dpci->dom = NULL;
list_del(&girq->list);
list_del(&digl->list);
@@ -402,8 +546,13 @@ int pt_irq_destroy_bind(
msixtbl_pt_unregister(d, pirq);
if ( pt_irq_need_timer(pirq_dpci->flags) )
kill_timer(&pirq_dpci->timer);
- pirq_dpci->dom = NULL;
pirq_dpci->flags = 0;
+ /*
+ * See comment in pt_irq_create_bind's PT_IRQ_TYPE_MSI before the
+ * call to pt_pirq_softirq_reset.
+ */
+ pt_pirq_softirq_reset(pirq_dpci);
+
pirq_cleanup_check(pirq, d);
}
@@ -426,14 +575,12 @@ void pt_pirq_init(struct domain *d, struct hvm_pirq_dpci
*dpci)
{
INIT_LIST_HEAD(&dpci->digl_list);
dpci->gmsi.dest_vcpu_id = -1;
- softirq_tasklet_init(&dpci->tasklet, hvm_dirq_assist, (unsigned long)dpci);
}
bool_t pt_pirq_cleanup_check(struct hvm_pirq_dpci *dpci)
{
- if ( !dpci->flags )
+ if ( !dpci->flags && !pt_pirq_softirq_active(dpci) )
{
- tasklet_kill(&dpci->tasklet);
dpci->dom = NULL;
return 1;
}
@@ -476,8 +623,7 @@ int hvm_do_IRQ_dpci(struct domain *d, struct pirq *pirq)
!(pirq_dpci->flags & HVM_IRQ_DPCI_MAPPED) )
return 0;
- pirq_dpci->masked = 1;
- tasklet_schedule(&pirq_dpci->tasklet);
+ raise_softirq_for(pirq_dpci);
return 1;
}
@@ -531,28 +677,12 @@ void hvm_dpci_msi_eoi(struct domain *d, int vector)
spin_unlock(&d->event_lock);
}
-static void hvm_dirq_assist(unsigned long arg)
+static void hvm_dirq_assist(struct domain *d, struct hvm_pirq_dpci *pirq_dpci)
{
- struct hvm_pirq_dpci *pirq_dpci = (struct hvm_pirq_dpci *)arg;
- struct domain *d = pirq_dpci->dom;
-
- /*
- * We can be racing with 'pt_irq_destroy_bind' - with us being scheduled
- * right before 'pirq_guest_unbind' gets called - but us not yet executed.
- *
- * And '->dom' gets cleared later in the destroy path. We exit and clear
- * 'masked' - which is OK as later in this code we would
- * do nothing except clear the ->masked field anyhow.
- */
- if ( !d )
- {
- pirq_dpci->masked = 0;
- return;
- }
ASSERT(d->arch.hvm_domain.irq.dpci);
spin_lock(&d->event_lock);
- if ( test_and_clear_bool(pirq_dpci->masked) )
+ if ( pirq_dpci->state )
{
struct pirq *pirq = dpci_pirq(pirq_dpci);
const struct dev_intx_gsi_link *digl;
@@ -654,3 +784,81 @@ void hvm_dpci_eoi(struct domain *d, unsigned int guest_gsi,
unlock:
spin_unlock(&d->event_lock);
}
+
+static void dpci_softirq(void)
+{
+ unsigned int cpu = smp_processor_id();
+ LIST_HEAD(our_list);
+
+ local_irq_disable();
+ list_splice_init(&per_cpu(dpci_list, cpu), &our_list);
+ local_irq_enable();
+
+ while ( !list_empty(&our_list) )
+ {
+ struct hvm_pirq_dpci *pirq_dpci;
+ struct domain *d;
+
+ pirq_dpci = list_entry(our_list.next, struct hvm_pirq_dpci,
softirq_list);
+ list_del(&pirq_dpci->softirq_list);
+
+ d = pirq_dpci->dom;
+ smp_mb(); /* 'd' MUST be saved before we set/clear the bits. */
+ if ( test_and_set_bit(STATE_RUN, &pirq_dpci->state) )
+ BUG();
+ /*
+ * The one who clears STATE_SCHED MUST refcount the domain.
+ */
+ if ( test_and_clear_bit(STATE_SCHED, &pirq_dpci->state) )
+ {
+ hvm_dirq_assist(d, pirq_dpci);
+ put_domain(d);
+ }
+ clear_bit(STATE_RUN, &pirq_dpci->state);
+ }
+}
+
+static int cpu_callback(
+ struct notifier_block *nfb, unsigned long action, void *hcpu)
+{
+ unsigned int cpu = (unsigned long)hcpu;
+
+ switch ( action )
+ {
+ case CPU_UP_PREPARE:
+ INIT_LIST_HEAD(&per_cpu(dpci_list, cpu));
+ break;
+ case CPU_UP_CANCELED:
+ case CPU_DEAD:
+ /*
+ * On CPU_DYING this callback is called (on the CPU that is dying)
+ * with an possible HVM_DPIC_SOFTIRQ pending - at which point we can
+ * clear out any outstanding domains (by the virtue of the idle loop
+ * calling the softirq later). In CPU_DEAD case the CPU is deaf and
+ * there are no pending softirqs for us to handle so we can chill.
+ */
+ ASSERT(list_empty(&per_cpu(dpci_list, cpu)));
+ break;
+ default:
+ break;
+ }
+
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block cpu_nfb = {
+ .notifier_call = cpu_callback,
+};
+
+static int __init setup_dpci_softirq(void)
+{
+ unsigned int cpu;
+
+ for_each_online_cpu(cpu)
+ INIT_LIST_HEAD(&per_cpu(dpci_list, cpu));
+
+ open_softirq(HVM_DPCI_SOFTIRQ, dpci_softirq);
+ register_cpu_notifier(&cpu_nfb);
+ return 0;
+}
+__initcall(setup_dpci_softirq);
diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
index 81e8a3a..8631473 100644
--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -767,40 +767,51 @@ static int pci_clean_dpci_irq(struct domain *d,
xfree(digl);
}
- tasklet_kill(&pirq_dpci->tasklet);
-
- return 0;
+ return pt_pirq_softirq_active(pirq_dpci) ? -ERESTART : 0;
}
-static void pci_clean_dpci_irqs(struct domain *d)
+static int pci_clean_dpci_irqs(struct domain *d)
{
struct hvm_irq_dpci *hvm_irq_dpci = NULL;
if ( !iommu_enabled )
- return;
+ return -ENODEV;
if ( !is_hvm_domain(d) )
- return;
+ return -EINVAL;
spin_lock(&d->event_lock);
hvm_irq_dpci = domain_get_irq_dpci(d);
if ( hvm_irq_dpci != NULL )
{
- pt_pirq_iterate(d, pci_clean_dpci_irq, NULL);
+ int ret = pt_pirq_iterate(d, pci_clean_dpci_irq, NULL);
+
+ if ( ret )
+ {
+ spin_unlock(&d->event_lock);
+ return ret;
+ }
d->arch.hvm_domain.irq.dpci = NULL;
free_hvm_irq_dpci(hvm_irq_dpci);
}
spin_unlock(&d->event_lock);
+ return 0;
}
-void pci_release_devices(struct domain *d)
+int pci_release_devices(struct domain *d)
{
struct pci_dev *pdev;
u8 bus, devfn;
+ int ret;
spin_lock(&pcidevs_lock);
- pci_clean_dpci_irqs(d);
+ ret = pci_clean_dpci_irqs(d);
+ if ( ret == -ERESTART )
+ {
+ spin_unlock(&pcidevs_lock);
+ return ret;
+ }
while ( (pdev = pci_get_pdev_by_domain(d, -1, -1, -1)) )
{
bus = pdev->bus;
@@ -811,6 +822,8 @@ void pci_release_devices(struct domain *d)
PCI_SLOT(devfn), PCI_FUNC(devfn));
}
spin_unlock(&pcidevs_lock);
+
+ return 0;
}
#define PCI_CLASS_BRIDGE_HOST 0x0600
diff --git a/xen/include/asm-x86/softirq.h b/xen/include/asm-x86/softirq.h
index 7225dea..ec787d6 100644
--- a/xen/include/asm-x86/softirq.h
+++ b/xen/include/asm-x86/softirq.h
@@ -7,7 +7,8 @@
#define MACHINE_CHECK_SOFTIRQ (NR_COMMON_SOFTIRQS + 3)
#define PCI_SERR_SOFTIRQ (NR_COMMON_SOFTIRQS + 4)
-#define NR_ARCH_SOFTIRQS 5
+#define HVM_DPCI_SOFTIRQ (NR_COMMON_SOFTIRQS + 5)
+#define NR_ARCH_SOFTIRQS 6
bool_t arch_skip_send_event_check(unsigned int cpu);
diff --git a/xen/include/xen/hvm/irq.h b/xen/include/xen/hvm/irq.h
index 94a550a..1db45b2 100644
--- a/xen/include/xen/hvm/irq.h
+++ b/xen/include/xen/hvm/irq.h
@@ -93,13 +93,14 @@ struct hvm_irq_dpci {
/* Machine IRQ to guest device/intx mapping. */
struct hvm_pirq_dpci {
uint32_t flags;
- bool_t masked;
+ unsigned int state;
+ int cpu;
uint16_t pending;
struct list_head digl_list;
struct domain *dom;
struct hvm_gmsi_info gmsi;
struct timer timer;
- struct tasklet tasklet;
+ struct list_head softirq_list;
};
void pt_pirq_init(struct domain *, struct hvm_pirq_dpci *);
@@ -109,6 +110,7 @@ int pt_pirq_iterate(struct domain *d,
struct hvm_pirq_dpci *, void *arg),
void *arg);
+bool_t pt_pirq_softirq_active(struct hvm_pirq_dpci *);
/* Modify state of a PCI INTx wire. */
void hvm_pci_intx_assert(
struct domain *d, unsigned int device, unsigned int intx);
diff --git a/xen/include/xen/pci.h b/xen/include/xen/pci.h
index 91520bc..5f295f3 100644
--- a/xen/include/xen/pci.h
+++ b/xen/include/xen/pci.h
@@ -99,7 +99,7 @@ struct pci_dev *pci_lock_domain_pdev(
void setup_hwdom_pci_devices(struct domain *,
int (*)(u8 devfn, struct pci_dev *));
-void pci_release_devices(struct domain *d);
+int pci_release_devices(struct domain *d);
int pci_add_segment(u16 seg);
const unsigned long *pci_get_ro_map(u16 seg);
int pci_add_device(u16 seg, u8 bus, u8 devfn, const struct pci_dev_info *);
--
1.8.0.1
Attachment:
0001-dpci-Replace-tasklet-with-an-softirq-v10.patch _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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