Re: [PATCH V6 0/6] Fast mmio eventfd fixes
From: Jason Wang
Date: Sun Nov 08 2015 - 23:36:34 EST
On 11/09/2015 01:11 AM, Michael S. Tsirkin wrote:
> On Tue, Sep 15, 2015 at 02:41:53PM +0800, Jason Wang wrote:
>> 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
>> 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?
>> Changes from V4:
>> - move the location of kvm_assign_ioeventfd() in patch 1 which reduce
>> the change set.
>> - commit log typo fixes
>> - switch to use kvm_deassign_ioeventfd_id) when fail to register to
>> fast mmio bus
>> - change kvm_io_bus_cmp() as Paolo's suggestions
>> - introduce a new capability to avoid new userspace crash old kernel
>> - add a new patch that only try to register mmio eventfd on fast mmio
>> 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 (6):
>> kvm: don't try to register to KVM_FAST_MMIO_BUS for non mmio eventfd
>> 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
>> kvm: add fast mmio capabilitiy
>> Documentation/virtual/kvm/api.txt | 7 ++-
>> arch/x86/kvm/trace.h | 18 ++++++
>> arch/x86/kvm/vmx.c | 1 +
>> arch/x86/kvm/x86.c | 1 +
>> include/uapi/linux/kvm.h | 1 +
>> virt/kvm/eventfd.c | 124 ++++++++++++++++++++++----------------
>> virt/kvm/kvm_main.c | 20 +++++-
>> 7 files changed, 118 insertions(+), 54 deletions(-)
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