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Re: [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask
From: |
Eduardo Habkost |
Subject: |
Re: [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask |
Date: |
Fri, 17 Jun 2016 12:27:37 -0300 |
User-agent: |
Mutt/1.6.1 (2016-04-27) |
On Fri, Jun 17, 2016 at 04:25:57PM +0200, Paolo Bonzini wrote:
>
>
> On 17/06/2016 15:41, Eduardo Habkost wrote:
> > In theory, we should never initialize anything on the machine
> > based on the host we are running. In practice we sometimes do
> > that, and we know it's unsafe. Sending the value on the migration
> > stream is a solution to detect when this breaks something. We did
> > that before, for TSC frequency.
> >
> > I prefer to add a little extra code, than to waste time debugging
> > when that stuff breaks.
>
> Fair enough (but still let's add and strip the 1s in pre_save and
> post_load). It is a good justification for sending configuration over
> the wire, that we initialize things based on the host we're running.
>
> But we shouldn't initialize more things based on the host (e.g. new
> booleans should be "enforce"-style).
Strongly agreed.
> Also I don't really like
> introducing sanity checks for those that aren't based on the host (as in
> the LMCE thread). This code will never trigger in practice, so it's
> just extra cost for no benefit.
Our experience with guest ABI and compatibility code tells me
otherwise. Keeping guest ABI is hard, so I would always support
adding extra code to help us catch mistakes (either in QEMU,
management software, or user mistakes).
--
Eduardo
- Re: [Qemu-devel] [PATCH 2/5] x86: Mask mtrr mask based on CPU physical address limits, (continued)
- [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask, Dr. David Alan Gilbert (git), 2016/06/16
- Re: [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask, Eduardo Habkost, 2016/06/16
- Re: [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask, Paolo Bonzini, 2016/06/17
- Re: [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask, Eduardo Habkost, 2016/06/17
- Re: [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask, Paolo Bonzini, 2016/06/17
- Re: [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask, Eduardo Habkost, 2016/06/17
- Re: [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask, Paolo Bonzini, 2016/06/17
- Re: [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask,
Eduardo Habkost <=
- Re: [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask, Paolo Bonzini, 2016/06/17
- Re: [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask, Eduardo Habkost, 2016/06/17
- Re: [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask, Dr. David Alan Gilbert, 2016/06/17
- Re: [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask, Paolo Bonzini, 2016/06/17
- Re: [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask, Dr. David Alan Gilbert, 2016/06/17
[Qemu-devel] [PATCH 5/5] x86: Set physical address bits based on host, Dr. David Alan Gilbert (git), 2016/06/16
[Qemu-devel] [PATCH 4/5] x86: Allow physical address bits to be set, Dr. David Alan Gilbert (git), 2016/06/16