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    SubjectRe: [PATCH v2 09/10] KVM: arm/arm64: Document KVM_DEV_ARM_ITS_CTRL_RESET
    Hi Eric,

    On Wed, Sep 27, 2017 at 03:28:39PM +0200, Eric Auger wrote:
    > At the moment, the in-kernel emulated ITS is not properly reset.
    > On guest restart/reset some registers keep their old values and
    > internal structures like device, ITE, collection lists are not freed.

    , and collection ...
    >
    > This may lead to various bugs. Among them, we can have incorrect state
    > backup or failure when saving the ITS state at early guest boot stage.
    >
    > This patch documents a new attribute, KVM_DEV_ARM_ITS_CTRL_RESET in
    > the KVM_DEV_ARM_VGIC_GRP_CTRL group.
    >
    > Upon this action, we can reset registers and especially those
    > pointing to tables previously allocated by the guest and free
    > the internal data structures storing the list of devices, collections
    > and lpis.
    >
    > Signed-off-by: Eric Auger <eric.auger@redhat.com>
    > Reported-by: wanghaibin <wanghaibin.wang@huawei.com>
    >
    > ---
    >
    > v1 -> v2:
    > - Describe architecturally-defined reset values
    > ---
    > Documentation/virtual/kvm/devices/arm-vgic-its.txt | 16 ++++++++++++++++
    > 1 file changed, 16 insertions(+)
    >
    > diff --git a/Documentation/virtual/kvm/devices/arm-vgic-its.txt b/Documentation/virtual/kvm/devices/arm-vgic-its.txt
    > index eb06beb..047358c 100644
    > --- a/Documentation/virtual/kvm/devices/arm-vgic-its.txt
    > +++ b/Documentation/virtual/kvm/devices/arm-vgic-its.txt
    > @@ -33,6 +33,10 @@ Groups:
    > request the initialization of the ITS, no additional parameter in
    > kvm_device_attr.addr.
    >
    > + KVM_DEV_ARM_ITS_CTRL_RESET
    > + reset the ITS, no additional parameter in kvm_device_attr.addr.
    > + See "ITS Reset State" section.
    > +
    > KVM_DEV_ARM_ITS_SAVE_TABLES
    > save the ITS table data into guest RAM, at the location provisioned
    > by the guest in corresponding registers/table entries.
    > @@ -157,3 +161,15 @@ Then vcpus can be started.
    > - pINTID is the physical LPI ID; if zero, it means the entry is not valid
    > and other fields are not meaningful.
    > - ICID is the collection ID
    > +
    > + ITS Reset State:
    > + ----------------

    Are the bullet points below the state after the device has been reset
    (after KVM_DEV_ARM_ITS_CTRL_RESET returns) or ? I think this should be
    clarified.

    > +
    > +- the ITS is not enabled and quiescent:

    The

    > + GITS_CTLR.Enabled = 0 .Quiescent=1
    > +- caches are empty
    Caches (would it make more sense to say that there is no
    internally cached state?)
    > +- No collection or device table is provisionned

    are used:

    > + GITS_BASER<n>.Valid = 0
    > +- the command queue is not allocated:

    The

    > + GITS_CBASER = 0, GITS_CREADR = 0, GITS_CWRITER = 0
    > +- The ABI version corresponds to the one set before reset

    Do you mean that resetting the ITS cannot change the ABI version used
    for save/restore, and therefore remains the same as it the version
    configured when the device was first created ?

    > --
    > 2.5.5
    >

    Thanks, (and sorry for being pedantic about ABI wordings)
    -Christoffer

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