lkml.org 
[lkml]   [2015]   [Sep]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH V4 0/4] Fast MMIO eventfd fixes
On Fri, Sep 11, 2015 at 11:17:33AM +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. 2 is fixed by ignore
> the actual length if the length of iodev is zero in kvm_io_bus_cmp().
>
> Please review.

I think we should add a capability for fast mmio.
This way, userspace can avoid crashing buggy kernels.

> Changes from V3:
>
> - Don't do search on two buses when trying to do write on
> KVM_MMIO_BUS. This fixes a small regression found by vmexit.flat.
> - Since we don't do search on two buses, change kvm_io_bus_cmp() to
> let it can find zero length iodevs.
> - Fix the unnecessary lines in tracepoint patch.
>
> Changes from V2:
> - Tweak styles and comment suggested by Cornelia.
>
> Changes from v1:
> - change ioeventfd_bus_from_flags() to return KVM_FAST_MMIO_BUS when
> needed to save lots of unnecessary changes.
>
> Jason Wang (4):
> kvm: factor out core eventfd assign/deassign logic
> kvm: fix double free for fast mmio eventfd
> kvm: fix zero length mmio searching
> kvm: add tracepoint for fast mmio
>
> arch/x86/kvm/trace.h | 18 ++++++++
> arch/x86/kvm/vmx.c | 1 +
> arch/x86/kvm/x86.c | 1 +
> virt/kvm/eventfd.c | 124 ++++++++++++++++++++++++++++++---------------------
> virt/kvm/kvm_main.c | 4 +-
> 5 files changed, 96 insertions(+), 52 deletions(-)
>
> --
> 2.1.4


\
 
 \ /
  Last update: 2015-09-11 10:21    [W:0.089 / U:0.044 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site