From: Jason Wang <jasowang@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: gleb@kernel.org, pbonzini@redhat.com, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, cornelia.huck@de.ibm.com
Subject: Re: [PATCH V3 2/3] kvm: don't register wildcard MMIO EVENTFD on two buses
Date: Mon, 31 Aug 2015 16:03:59 +0800 [thread overview]
Message-ID: <55E40A6F.5010003@redhat.com> (raw)
In-Reply-To: <20150831102838-mutt-send-email-mst@redhat.com>
On 08/31/2015 03:29 PM, Michael S. Tsirkin wrote:
>>>>> Thinking more about this, invoking the 0-length write after
>>>>> > >> > the != 0 length one would be better: it would mean we only
>>>>> > >> > handle the userspace MMIO like this.
>>> > > Right.
>>> > >
>> >
>> > Using current unittest. This patch is about 2.9% slower than before, and
>> > invoking 0-length write after is still 1.1% slower (mmio-datamatch-eventfd).
>> >
>> > /patch/result/-+%/
>> > /base/2957/0/
>> > /V3/3043/+2.9%/
>> > /V3+invoking != 0 length first/2990/+1.1%/
>> >
>> > So looks like the best method is not searching KVM_FAST_MMIO_BUS during
>> > KVM_MMIO_BUS. Instead, let userspace to register both datamatch and
>> > wildcard in this case. Does this sound good to you?
> No - we can't change userspace.
Actually, the change was as simple as following. So I don't get the
reason why.
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 9935029..42ee986 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -288,6 +288,8 @@ static int
virtio_pci_set_host_notifier_internal(VirtIOPCIProxy *proxy,
if (modern) {
memory_region_add_eventfd(modern_mr, modern_addr, 2,
true, n, notifier);
+ memory_region_add_eventfd(modern_mr, modern_addr, 0,
+ false, n, notifier);
}
if (legacy) {
memory_region_add_eventfd(legacy_mr, legacy_addr, 2,
@@ -297,6 +299,8 @@ static int
virtio_pci_set_host_notifier_internal(VirtIOPCIProxy *proxy,
if (modern) {
memory_region_del_eventfd(modern_mr, modern_addr, 2,
true, n, notifier);
+ memory_region_del_eventfd(modern_mr, modern_addr, 0,
+ false, n, notifier);
}
if (legacy) {
memory_region_del_eventfd(legacy_mr, legacy_addr, 2,
next prev parent reply other threads:[~2015-08-31 8:04 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-25 9:05 [PATCH V3 1/3] kvm: use kmalloc() instead of kzalloc() during iodev register/unregister Jason Wang
2015-08-25 9:05 ` [PATCH V3 2/3] kvm: don't register wildcard MMIO EVENTFD on two buses Jason Wang
2015-08-25 10:24 ` Cornelia Huck
2015-08-25 11:37 ` Michael S. Tsirkin
2015-08-25 11:51 ` Michael S. Tsirkin
2015-08-26 5:10 ` Jason Wang
2015-08-31 3:12 ` Jason Wang
2015-08-31 7:29 ` Michael S. Tsirkin
2015-08-31 8:03 ` Jason Wang [this message]
2015-08-31 11:33 ` Michael S. Tsirkin
2015-09-01 3:33 ` Jason Wang
2015-09-01 4:31 ` Michael S. Tsirkin
2015-09-01 4:47 ` Jason Wang
2015-09-01 6:54 ` Michael S. Tsirkin
2015-09-01 8:22 ` Jason Wang
2015-09-01 8:32 ` Michael S. Tsirkin
2015-08-25 9:05 ` [PATCH V3 3/3] kvm: add tracepoint for fast mmio Jason Wang
2015-08-25 11:36 ` Michael S. Tsirkin
2015-09-07 10:33 ` [PATCH V3 1/3] kvm: use kmalloc() instead of kzalloc() during iodev register/unregister Paolo Bonzini
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