On 07/24/2011 09:15 AM, Sasha Levin wrote:
Currently the method of dealing with an IO operation on a bus (PIO/MMIO)
is to call the read or write callback for each device registered
on the bus until we find a device which handles it.
Since the number of devices on a bus can be significant due to ioeventfds
and coalesced MMIO zones, this leads to a lot of overhead on each IO
operation.
Instead of registering devices, we now register ranges which points to
a device. Lookup is done using an efficient bsearch instead of a linear
search.
Performance test was conducted by comparing exit count per second with
200 ioeventfds created on one byte and the guest is trying to access a
different byte continuously (triggering usermode exits).
Before the patch the guest has achieved 259k exits per second, after the
patch the guest does 274k exits per second.
diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index efad723..094e057 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -713,14 +713,15 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags)
kvm_register_irq_mask_notifier(kvm, 0,&pit->mask_notifier);
kvm_iodevice_init(&pit->dev,&pit_dev_ops);
- ret = kvm_io_bus_register_dev(kvm, KVM_PIO_BUS,&pit->dev);
+ ret = kvm_io_bus_register_dev(kvm, KVM_PIO_BUS, KVM_PIT_BASE_ADDRESS, KVM_PIT_MEM_LENGTH,&pit->dev);
Long line.
-static inline struct kvm_pic *to_pic(struct kvm_io_device *dev)
+static inline struct kvm_pic *to_pic(struct kvm_io_device *dev, gpa_t addr)
{
- return container_of(dev, struct kvm_pic, dev);
+ switch (addr) {
+ case 0x20:
+ case 0x21:
+ return container_of(dev, struct kvm_pic, dev_master);
+ case 0xa0:
+ case 0xa1:
+ return container_of(dev, struct kvm_pic, dev_slave);
+ case 0x4d0:
+ case 0x4d1:
+ return container_of(dev, struct kvm_pic, dev_eclr);
+ }
+
+ return NULL;
}
Somewhat ugly. I think
int picdev_write_master(...)
{
return pcidev_write(container_of(...), ...);
}
is nicer, no?
@@ -560,16 +572,36 @@ struct kvm_pic *kvm_create_pic(struct kvm *kvm)
/*
* Initialize PIO device
*/
- kvm_iodevice_init(&s->dev,&picdev_ops);
+ kvm_iodevice_init(&s->dev_master,&picdev_ops);
+ kvm_iodevice_init(&s->dev_slave,&picdev_ops);
+ kvm_iodevice_init(&s->dev_eclr,&picdev_ops);
mutex_lock(&kvm->slots_lock);
- ret = kvm_io_bus_register_dev(kvm, KVM_PIO_BUS,&s->dev);
+ ret = kvm_io_bus_register_dev(kvm, KVM_PIO_BUS, 0x20, 2,&s->dev_master);
+ if (ret< 0)
+ goto fail_unlock;
+
+ ret = kvm_io_bus_register_dev(kvm, KVM_PIO_BUS, 0xa0, 2,&s->dev_slave);
+ if (ret< 0)
+ goto fail_unlock;
+
+ ret = kvm_io_bus_register_dev(kvm, KVM_PIO_BUS, 0x4d0, 2,&s->dev_eclr);
+ if (ret< 0)
+ goto fail_unlock;
+
mutex_unlock(&kvm->slots_lock);
- if (ret< 0) {
- kfree(s);
- return NULL;
- }
return s;
+
+fail_unlock:
+
+ mutex_unlock(&kvm->slots_lock);
+ kvm_io_bus_unregister_dev(kvm, KVM_PIO_BUS,&s->dev_master);
+ kvm_io_bus_unregister_dev(kvm, KVM_PIO_BUS,&s->dev_slave);
+ kvm_io_bus_unregister_dev(kvm, KVM_PIO_BUS,&s->dev_eclr);
+
+ kfree(s);
+
+ return NULL;
}
You're unregistering devices that were never registered. It may work
now, but it's fragile.
if (ret< 0)
goto out_free_dev;
list_add_tail(&dev->list,&kvm->coalesced_zones);
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 73358d2..f59c1e8 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -586,7 +586,8 @@ kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
kvm_iodevice_init(&p->dev,&ioeventfd_ops);
- ret = kvm_io_bus_register_dev(kvm, bus_idx,&p->dev);
+ ret = kvm_io_bus_register_dev(kvm, bus_idx, p->addr, p->length,
+ &p->dev);
Should this be p->length or 1?
#include<asm/processor.h>
#include<asm/io.h>
@@ -2391,24 +2393,94 @@ static void kvm_io_bus_destroy(struct kvm_io_bus *bus)
int i;
for (i = 0; i< bus->dev_count; i++) {
- struct kvm_io_device *pos = bus->devs[i];
+ struct kvm_io_device *pos = bus->range[i].dev;
This will call the destructor three times for the PIC. Is this safe?
--
error compiling committee.c: too many arguments to function
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