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Re: [Qemu-devel] [PATCH 3/3] e1000: Old machine types, turn new subsecti
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH 3/3] e1000: Old machine types, turn new subsection off |
Date: |
Tue, 27 Mar 2018 19:01:16 +0100 |
User-agent: |
Mutt/1.9.2 (2017-12-15) |
* Paolo Bonzini (address@hidden) wrote:
> On 27/03/2018 18:47, Dr. David Alan Gilbert wrote:
> >> So if the subsection is absent you
> >> have to migrate either tx.tso_props or tx.props, depending on s->tx.cptse.
> > Do you mean when sending you have to decide which set to send in the
> > non-subsection data? And with cptse true that means use tso_props?
>
> Yes.
>
> >> Likewise if you migrate from older versions: if s->tx.props.tse &&
> >> s->tx.cptse, you have to copy s->tx.props to s->tx.tso_props and clear
> >> s->tx.props.
> >
> > I don't see any equivalent code in the existing non-subsection postload to
> > do this; so I'm guessing there are some cases of 2.11->2.12 that will
> > break at the moment?
>
> Yes, I think so.
OK, so we'd better fix that for 2.12.
> >> My understanding is that s->tx.tso_props.tse will be 1 if
> >> and only if the source sent s->tx.tso_props.
> > I don't see anything in the current code that migrates tso_props.tse -
> > where does it come from?
>
> Ouch... The tse field is more or less dead in current code AFAICS, but
> it was used in the previous version. What's the best way then to find
> if the subsection was transmitted? Do we have anything like a post_load
> callback in the subsection itself?
Yes, if I just add a .post_load field in the subsection it should get
called.
> To find out which "props" to transmit to older QEMU, you can add a
> tp->use_tso_for_migration = tp->cptse just before "if (!(txd_lower &
> E1000_TXD_CMD_EOP))" in process_tx_desc...
OK.
> >> This seems most easily done with a new field (e.g. vmstate_fixed_props)
> >> that is written in pre_save and set in post_load.
> > It might need a VMSTATE_WITH_TMP to be able to do the saving part;
> > when saving we can't change the current state when migrating
> > to an old destination in case the migration fails and we just continue.
>
> Perhaps you can just copy props/tso_props to a new field, and change all the
>
> VMSTATE_UINT8(tx.props.ipcss, E1000State),
> VMSTATE_UINT8(tx.props.ipcso, E1000State),
> VMSTATE_UINT16(tx.props.ipcse, E1000State),
>
> to
>
> VMSTATE_UINT8(tx_legacy_vmstate_props.ipcss, E1000State),
> ...
>
> and then add tx.props to the subsection together with tso.props.
>
> New->old migration will place tx_legacy_vmstate_props in tx.props on the
> destination; new->new will realize the subsection was transmitted and
> ignore the tx_legacy_vmstate_props; old->new will not find data from the
> subsection and copy the tx_legacy_vmstate_props into one of tx.props and
> tx.tso_props.
Yeh, adding a legacy_props field should do it; although we never need
to transmit more than 2 copies.
I'll look at this more tomorrow; I am a bit worried about testing it
though.
Dave
> Paolo
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- [Qemu-devel] [PATCH 0/3] e1000 migration changes for 2.12, Dr. David Alan Gilbert (git), 2018/03/27
- [Qemu-devel] [PATCH 3/3] e1000: Old machine types, turn new subsection off, Dr. David Alan Gilbert (git), 2018/03/27
- Re: [Qemu-devel] [PATCH 3/3] e1000: Old machine types, turn new subsection off, Paolo Bonzini, 2018/03/27
- Re: [Qemu-devel] [PATCH 3/3] e1000: Old machine types, turn new subsection off, Dr. David Alan Gilbert, 2018/03/27
- Re: [Qemu-devel] [PATCH 3/3] e1000: Old machine types, turn new subsection off, Paolo Bonzini, 2018/03/27
- Re: [Qemu-devel] [PATCH 3/3] e1000: Old machine types, turn new subsection off,
Dr. David Alan Gilbert <=
- Re: [Qemu-devel] [PATCH 3/3] e1000: Old machine types, turn new subsection off, Paolo Bonzini, 2018/03/27
- Re: [Qemu-devel] [PATCH 3/3] e1000: Old machine types, turn new subsection off, Ed Swierk, 2018/03/27
[Qemu-devel] [PATCH 2/3] e1000: wire new subsection to property, Dr. David Alan Gilbert (git), 2018/03/27
[Qemu-devel] [PATCH 1/3] e1000: Convert v3 fields to subsection, Dr. David Alan Gilbert (git), 2018/03/27
Re: [Qemu-devel] [PATCH 0/3] e1000 migration changes for 2.12, Jason Wang, 2018/03/27
Re: [Qemu-devel] [PATCH 0/3] e1000 migration changes for 2.12, Juan Quintela, 2018/03/27