linux-kernel - Re: [PATCH v6 0/9] vITS Migration fixes and reset

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Date:   Mon, 30 Oct 2017 07:20:32 +0100
From:   Christoffer Dall <cdall@...aro.org>
To:     Eric Auger <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, kvmarm@...ts.cs.columbia.edu,
        marc.zyngier@....com, peter.maydell@...aro.org,
        andre.przywara@....com, wanghaibin.wang@...wei.com,
        wu.wubin@...wei.com, drjones@...hat.com, wei@...hat.com
Subject: Re: [PATCH v6 0/9] vITS Migration fixes and reset

Hi Eric,

On Thu, Oct 26, 2017 at 05:23:02PM +0200, Eric Auger wrote:
> This series fixes various bugs observed when saving/restoring the
> ITS state before the guest writes the ITS registers (on first boot or
> after reset/reboot).
> 
> This is a follow up of Wanghaibin's series [1] plus additional
> patches following additional code review. It also proposes one
> ITS reset implementation.
> 
> Currently, the in-kernel emulated ITS is not reset. After a
> reset/reboot, the ITS register values and caches are left
> unchanged. Registers may point to some tables in guest memory
> which do not exist anymore. If an ITS state backup is initiated
> before the guest re-writes the registers, the save fails
> because inconsistencies are detected. Also restore of data saved
> as such moment is failing.
> 
> Patches [1-4] are fixes of bugs observed during migration at
> early guets boot stage.
> - handle case where all collection, device and ITT entries are
>   invalid on restore (which is not an error)
> - Check the GITS_BASER<n> valid bit before attempting the save
>   any table
> - Check the GITS_BASER<n> and GITS_CBASER are valid before enabling
>   the ITS
> 
> Patches [5-9] allow to empty the caches on reset and implement a
> new ITS reset IOCTL

I applied patches 1-4 to kvmarm/master and included them in a late pull
request to kvm.

I also took the remaining patches with the adjusted comment in
kvmarm/next.

One question:  Don't we have a remaining issue to support saving the
collection table even if the device table is inconsistent and vice
versa?  Are you planning on picking up that work?

Thanks,
-Christoffer