linux-kernel - Re: [RFC PATCH v1 3/4] KVM: arm64: GICv4.1: Restore VLPI's pending state to physical side

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <274dafb2e21f49326a64bb575e668793@kernel.org>
Date:   Tue, 01 Dec 2020 11:50:00 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Shenming Lu <lushenming@...wei.com>
Cc:     James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Eric Auger <eric.auger@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Christoffer Dall <christoffer.dall@....com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kirti Wankhede <kwankhede@...dia.com>,
        Cornelia Huck <cohuck@...hat.com>, Neo Jia <cjia@...dia.com>,
        wanghaibin.wang@...wei.com, yuzenghui@...wei.com
Subject: Re: [RFC PATCH v1 3/4] KVM: arm64: GICv4.1: Restore VLPI's pending
 state to physical side

On 2020-12-01 11:40, Shenming Lu wrote:
> On 2020/12/1 18:55, Marc Zyngier wrote:
>> On 2020-11-30 07:23, Shenming Lu wrote:
>> 
>> Hi Shenming,
>> 
>>> We are pondering over this problem these days, but still don't get a
>>> good solution...
>>> Could you give us some advice on this?
>>> 
>>> Or could we move the restoring of the pending states (include the 
>>> sync
>>> from guest RAM and the transfer to HW) to the GIC VM state change 
>>> handler,
>>> which is completely corresponding to save_pending_tables (more 
>>> symmetric?)
>>> and don't expose GICv4...
>> 
>> What is "the GIC VM state change handler"? Is that a QEMU thing?
> 
> Yeah, it is a a QEMU thing...
> 
>> We don't really have that concept in KVM, so I'd appreciate if you 
>> could
>> be a bit more explicit on this.
> 
> My thought is to add a new interface (to QEMU) for the restoring of
> the pending states, which is completely corresponding to
> KVM_DEV_ARM_VGIC_SAVE_PENDING_TABLES...
> And it is called from the GIC VM state change handler in QEMU, which
> is happening after the restoring (call kvm_vgic_v4_set_forwarding())
> but before the starting (running) of the VFIO device.

Right, that makes sense. I still wonder how much the GIC save/restore
stuff differs from other architectures that implement similar features,
such as x86 with VT-D.

It is obviously too late to change the userspace interface, but I wonder
whether we missed something at the time.

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...