The allocation size of the kvm_irq_routing_table depends on
the number of irq routing entries because they are all
allocated with one kzalloc call.
When the irq routing table gets bigger this requires high
order allocations which fail from time to time:
qemu-kvm: page allocation failure: order:4, mode:0xd0
This patch fixes this issue by breaking up the allocation of
the table and its entries into individual kzalloc calls.
These could all be satisfied with order-0 allocations, which
are less likely to fail.
The downside of this change is the lower performance, because
of more calls to kzalloc. But given how often kvm_set_irq_routing
is called in the lifetime of a guest, it doesn't really
matter much.
Signed-off-by: Joerg Roedel <jroedel@suse.de>
[Avoid sparse warning through rcu_access_pointer. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This moves the functions kvm_irq_has_notifier(), kvm_notify_acked_irq(),
kvm_register_irq_ack_notifier() and kvm_unregister_irq_ack_notifier()
from irqchip.c to eventfd.c. The reason for doing this is that those
functions are used in connection with IRQFDs, which are implemented in
eventfd.c. In future we will want to use IRQFDs on platforms that
don't implement the GSI routing implemented in irqchip.c, so we won't
be compiling in irqchip.c, but we still need the irq notifiers. The
implementation is unchanged.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Tested-by: Eric Auger <eric.auger@linaro.org>
Tested-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Now that struct _irqfd does not keep a reference to storage pointed
to by the irq_routing field of struct kvm, we can move the statement
that updates it out from under the irqfds.lock and put it in
kvm_set_irq_routing() instead. That means we then have to take a
srcu_read_lock on kvm->irq_srcu around the irqfd_update call in
kvm_irqfd_assign(), since holding the kvm->irqfds.lock no longer
ensures that that the routing can't change.
Combined with changing kvm_irq_map_gsi() and kvm_irq_map_chip_pin()
to take a struct kvm * argument instead of the pointer to the routing
table, this allows us to to move all references to kvm->irq_routing
into irqchip.c. That in turn allows us to move the definition of the
kvm_irq_routing_table struct into irqchip.c as well.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Tested-by: Eric Auger <eric.auger@linaro.org>
Tested-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This provides accessor functions for the KVM interrupt mappings, in
order to reduce the amount of code that accesses the fields of the
kvm_irq_routing_table struct, and restrict that code to one file,
virt/kvm/irqchip.c. The new functions are kvm_irq_map_gsi(), which
maps from a global interrupt number to a set of IRQ routing entries,
and kvm_irq_map_chip_pin, which maps from IRQ chip and pin numbers to
a global interrupt number.
This also moves the update of kvm_irq_routing_table::chip[][]
into irqchip.c, out of the various kvm_set_routing_entry
implementations. That means that none of the kvm_set_routing_entry
implementations need the kvm_irq_routing_table argument anymore,
so this removes it.
This does not change any locking or data lifetime rules.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Tested-by: Eric Auger <eric.auger@linaro.org>
Tested-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When starting lots of dataplane devices the bootup takes very long on
Christian's s390 with irqfd patches. With larger setups he is even
able to trigger some timeouts in some components. Turns out that the
KVM_SET_GSI_ROUTING ioctl takes very long (strace claims up to 0.1 sec)
when having multiple CPUs. This is caused by the synchronize_rcu and
the HZ=100 of s390. By changing the code to use a private srcu we can
speed things up. This patch reduces the boot time till mounting root
from 8 to 2 seconds on my s390 guest with 100 disks.
Uses of hlist_for_each_entry_rcu, hlist_add_head_rcu, hlist_del_init_rcu
are fine because they do not have lockdep checks (hlist_for_each_entry_rcu
uses rcu_dereference_raw rather than rcu_dereference, and write-sides
do not do rcu lockdep at all).
Note that we're hardly relying on the "sleepable" part of srcu. We just
want SRCU's faster detection of grace periods.
Testing was done by Andrew Theurer using netperf tests STREAM, MAERTS
and RR. The difference between results "before" and "after" the patch
has mean -0.2% and standard deviation 0.6%. Using a paired t-test on the
data points says that there is a 2.5% probability that the patch is the
cause of the performance difference (rather than a random fluctuation).
(Restricting the t-test to RR, which is the most likely to be affected,
changes the numbers to respectively -0.3% mean, 0.7% stdev, and 8%
probability that the numbers actually say something about the patch.
The probability increases mostly because there are fewer data points).
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com> # s390
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Setting up IRQ routes is nothing IOAPIC specific. Extract everything
that really is generic code into irqchip.c and only leave the ioapic
specific bits to irq_comm.c.
Signed-off-by: Alexander Graf <agraf@suse.de>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
The current irq_comm.c file contains pieces of code that are generic
across different irqchip implementations, as well as code that is
fully IOAPIC specific.
Split the generic bits out into irqchip.c.
Signed-off-by: Alexander Graf <agraf@suse.de>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Joerg Roedel
Kevin Mulvey
Paul Mackerras
Christian Borntraeger
Alexander Graf