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Re: [PATCH] spapr: Fix VSMT mode when it is not supported by the kernel
From: |
David Gibson |
Subject: |
Re: [PATCH] spapr: Fix VSMT mode when it is not supported by the kernel |
Date: |
Tue, 19 Nov 2019 12:00:12 +1100 |
User-agent: |
Mutt/1.12.1 (2019-06-15) |
On Fri, Nov 08, 2019 at 05:47:59PM +0100, Greg Kurz wrote:
> On Fri, 8 Nov 2019 16:40:35 +0100
> Laurent Vivier <address@hidden> wrote:
>
> > Commit 29cb4187497d sets by default the VSMT to smp_threads,
> > but older kernels (< 4.13) don't support that.
> >
> > We can reasonably restore previous behavior with this kernel
> > to allow to run QEMU as before.
> >
> > If VSMT is not supported, VSMT will be set to MAX(8, smp_threads)
> > as it is done for previous machine types (< pseries-4.2)
> >
>
> It is usually _bad_ to base the machine behavior on host capabilities.
> What happens if we migrate between an older kernel and a recent one ?
Right. We're really trying to remove instaces of such behaviour. I'd
prefer to completely revert Greg's original patch than to re-introduce
host configuration dependency into the guest configuration..
> I understand this is to fix tests/migration-test on older kernels.
> Couldn't this be achieved with migration-test doing some introspection
> and maybe pass vsmt=8 on the QEMU command line ?
..adjusting the test case like this might be a better idea, though.
What's the test setup where we're using the old kernel? I really only
applied the original patch on the guess that we didn't really care
about kernels that old. The fact you've hit this in practice makes me
doubt that assumption.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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- [PATCH] spapr: Fix VSMT mode when it is not supported by the kernel, Laurent Vivier, 2019/11/08
- Re: [PATCH] spapr: Fix VSMT mode when it is not supported by the kernel, Greg Kurz, 2019/11/08
- Re: [PATCH] spapr: Fix VSMT mode when it is not supported by the kernel, Laurent Vivier, 2019/11/08
- Re: [PATCH] spapr: Fix VSMT mode when it is not supported by the kernel,
David Gibson <=
- Re: [PATCH] spapr: Fix VSMT mode when it is not supported by the kernel, David Gibson, 2019/11/19
- Re: [PATCH] spapr: Fix VSMT mode when it is not supported by the kernel, Greg Kurz, 2019/11/20
- Re: [PATCH] spapr: Fix VSMT mode when it is not supported by the kernel, Laurent Vivier, 2019/11/20
- Re: [PATCH] spapr: Fix VSMT mode when it is not supported by the kernel, Laurent Vivier, 2019/11/20
- Re: [PATCH] spapr: Fix VSMT mode when it is not supported by the kernel, David Gibson, 2019/11/20
- Re: [PATCH] spapr: Fix VSMT mode when it is not supported by the kernel, Laurent Vivier, 2019/11/20