linux-kernel - Re: [PATCH V3 2/3] kvm: don't register wildcard MMIO EVENTFD on two buses

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <55E40A6F.5010003@redhat.com>
Date:	Mon, 31 Aug 2015 16:03:59 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
CC:	gleb@...nel.org, pbonzini@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, cornelia.huck@...ibm.com
Subject: Re: [PATCH V3 2/3] kvm: don't register wildcard MMIO EVENTFD on two
 buses



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,

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/