From: Auger Eric <eric.auger@redhat.com>
To: Christoffer Dall <cdall@linaro.org>
Cc: kvm@vger.kernel.org, marc.zyngier@arm.com,
andre.przywara@arm.com, linux-kernel@vger.kernel.org,
kvmarm@lists.cs.columbia.edu, wu.wubin@huawei.com,
eric.auger.pro@gmail.com
Subject: Re: [PATCH v6 0/9] vITS Migration fixes and reset
Date: Mon, 30 Oct 2017 08:59:36 +0100 [thread overview]
Message-ID: <cd3ef7af-38c1-fa3a-0ebc-5b731857865b@redhat.com> (raw)
In-Reply-To: <20171030062032.GL2166@lvm>
Hi Christoffer,
On 30/10/2017 07:20, Christoffer Dall wrote:
> 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.
OK Thanks.
>
> 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?
Actually to make it clear, patches 1-4 don't fix all failures but we
discussed at KVM forum that we shouldn't try to fix all of them without
a proper ITS reset implementation. So indeed even with patches 1-4 you
can get the migration failing as the save can happen after a reset,
in-between the collection creation and the PCIe device MSI registration.
This happens because the caches are not void and the L1 device table
entries are not valid. In that case the device table save fails and we
get no chance to save the collection as we abort the save immediately.
So on restore, guest will not work properly.
But on top of kvmarm/next, caches are void and we shouldn't face this
issue anymore. So in case the device table save fails, I think it still
makes sense to return an error.
But this means that the migration of ITS at early guest boot stage only
is fixed on kvmarm/next.
Thanks
Eric
>
> Thanks,
> -Christoffer
>
next prev parent reply other threads:[~2017-10-30 7:58 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-26 15:23 [PATCH v6 0/9] vITS Migration fixes and reset Eric Auger
2017-10-26 15:23 ` [PATCH v6 1/9] KVM: arm/arm64: vgic-its: Fix return value for device table restore Eric Auger
2017-10-26 15:23 ` [PATCH v6 2/9] KVM: arm/arm64: vgic-its: Fix vgic_its_restore_collection_table returned value Eric Auger
2017-11-02 5:50 ` Christoffer Dall
2017-10-26 15:23 ` [PATCH v6 3/9] KVM: arm/arm64: vgic-its: Check CBASER/BASER validity before enabling the ITS Eric Auger
2017-10-26 15:23 ` [PATCH v6 4/9] KVM: arm/arm64: vgic-its: Check GITS_BASER Valid bit before saving tables Eric Auger
2017-10-26 15:23 ` [PATCH v6 5/9] KVM: arm/arm64: vgic-its: Remove kvm_its_unmap_device Eric Auger
2017-10-30 2:49 ` Marc Zyngier
2017-10-26 15:23 ` [PATCH v6 6/9] KVM: arm/arm64: vgic-its: New helper functions to free the caches Eric Auger
2017-10-30 3:20 ` Marc Zyngier
2017-10-26 15:23 ` [PATCH v6 7/9] KVM: arm/arm64: vgic-its: Free caches when GITS_BASER Valid bit is cleared Eric Auger
2017-10-30 3:19 ` Marc Zyngier
2017-10-30 6:05 ` Christoffer Dall
2017-10-26 15:23 ` [PATCH v6 8/9] KVM: arm/arm64: Document KVM_DEV_ARM_ITS_CTRL_RESET Eric Auger
2017-10-30 3:21 ` Marc Zyngier
2017-10-30 6:06 ` Christoffer Dall
2017-10-26 15:23 ` [PATCH v6 9/9] KVM: arm/arm64: vgic-its: Implement KVM_DEV_ARM_ITS_CTRL_RESET Eric Auger
2017-10-30 3:22 ` Marc Zyngier
2017-10-30 6:11 ` Christoffer Dall
2017-10-30 6:20 ` [PATCH v6 0/9] vITS Migration fixes and reset Christoffer Dall
2017-10-30 7:59 ` Auger Eric [this message]
2017-10-31 6:43 ` Christoffer Dall
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=cd3ef7af-38c1-fa3a-0ebc-5b731857865b@redhat.com \
--to=eric.auger@redhat.com \
--cc=andre.przywara@arm.com \
--cc=cdall@linaro.org \
--cc=eric.auger.pro@gmail.com \
--cc=kvm@vger.kernel.org \
--cc=kvmarm@lists.cs.columbia.edu \
--cc=linux-kernel@vger.kernel.org \
--cc=marc.zyngier@arm.com \
--cc=wu.wubin@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox