On Mon, Oct 23 2017 at 4:08:28 pm BST, Eric Auger <eric.auger@xxxxxxxxxx> 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, and collection lists are not > freed. > > 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. > > The usual approach for device reset of having userspace write > the reset values of the registers to the kernel via the register > read/write APIs doesn't work for the ITS because it has some > internal state (caches) which is not exposed as registers, > and there is no register interface for "drop cached data without > writing it back to RAM". So we need a KVM API which mimics the > hardware's reset line, to provide the equivalent behaviour to > a "pull the power cord out of the back of the machine" reset. > > Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx> > Reported-by: wanghaibin <wanghaibin.wang@xxxxxxxxxx> > > --- > v4 -> v5: > - some rewording according to Christoffer's comments > > v2 -> v3: > - reword commit message, credit to Peter Maydell. > - take into account Christoffer rewording comments but still > kept details. Added Peter's comment but still kept details. > Peter may disagree. > > v1 -> v2: > - Describe architecturally-defined reset values > --- > Documentation/virtual/kvm/devices/arm-vgic-its.txt | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/Documentation/virtual/kvm/devices/arm-vgic-its.txt b/Documentation/virtual/kvm/devices/arm-vgic-its.txt > index eb06beb..d12d8e9 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 +161,20 @@ 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: > + ---------------- > + > +RESET returns the ITS to the same state that it was when first created and > +initialized. When the RESET command returns, the following things are > +guaranteed: > + > +- The ITS is not enabled and quiescent > + GITS_CTLR.Enabled = 0 .Quiescent=1 > +- There is no internally cached state > +- No collection or device table are used > + GITS_BASER<n>.Valid = 0 > +- The command queue is not allocated: I don't think we should say anything like that. Allocation is a guest thing, and hasn't much to do with the ITS itself. Specifying the state of the various registers should be enough. > + GITS_CBASER = 0, GITS_CREADR = 0, GITS_CWRITER = 0 > +- The ABI version is unchanged and remains the one set when the ITS > + device was first created. Thanks, M. -- Jazz is not dead. It just smells funny.
