linux-kernel - Re: [PATCH V6 0/6] Fast mmio eventfd fixes

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Date:	Tue, 10 Nov 2015 14:25:26 +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 V6 0/6] Fast mmio eventfd fixes



On 11/10/2015 04:19 AM, Michael S. Tsirkin wrote:
> On Mon, Nov 09, 2015 at 12:35:45PM +0800, Jason Wang wrote:
>> > 
>> > 
>> > On 11/09/2015 01:11 AM, Michael S. Tsirkin wrote:
>>> > > On Tue, Sep 15, 2015 at 02:41:53PM +0800, Jason Wang wrote:
>>>> > >> Hi:
>>>> > >>
>>>> > >> This series fixes two issues of fast mmio eventfd:
>>>> > >>
>>>> > >> 1) A single iodev instance were registerd on two buses: KVM_MMIO_BUS
>>>> > >>    and KVM_FAST_MMIO_BUS. This will cause double in
>>>> > >>    ioeventfd_destructor()
>>>> > >> 2) A zero length iodev on KVM_MMIO_BUS will never be found but
>>>> > >>    kvm_io_bus_cmp(). This will lead e.g the eventfd will be trapped by
>>>> > >>    qemu instead of host.
>>>> > >>
>>>> > >> 1 is fixed by allocating two instances of iodev and introduce a new
>>>> > >> capability for userspace. 2 is fixed by ignore the actual length if
>>>> > >> the length of iodev is zero in kvm_io_bus_cmp().
>>>> > >>
>>>> > >> Please review.
>>>> > >> Changes from V5:
>>>> > >> - move patch of explicitly checking for KVM_MMIO_BUS to patch 1 and
>>>> > >>   remove the unnecessary checks
>>>> > >> - even more grammar and typo fixes
>>>> > >> - rabase to kvm.git
>>>> > >> - document KVM_CAP_FAST_MMIO
>>> > > What's up with userspace using this capability?
>> > 
>> > It was renamed to KVM_CAP_IOEVENTFD_ANY_LENGTH.
>> > 
>>> > > Did patches ever get posted?
>> > 
>> > See https://lkml.org/lkml/2015/9/28/208
> Talking about userspace here.
> QEMU freeze is approaching, it really should
> use this to avoid regressions.
>

The patches were posted at
http://lists.gnu.org/archive/html/qemu-devel/2015-11/msg01276.html

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