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From: | Alexander Graf |
Subject: | Re: [Qemu-devel] [PATCH 3/3] S390: Enable -cpu help and QMP query-cpu-definitions |
Date: | Wed, 12 Dec 2012 19:23:17 +0100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:10.0.3) Gecko/20120306 Thunderbird/10.0.3 |
On 12/12/2012 05:28 PM, Andreas Färber wrote:
Am 12.12.2012 16:05, schrieb Viktor Mihajlovski:On 12/12/2012 02:51 PM, Andreas Färber wrote:+ (*cpu_fprintf)(f, "s390 %16s\n", "[host]");Note that the square-bracket notation was specific to x86 when it distinguished between built-in and config-based models.OK, since libvirt capable of dealing with s390 cpu models will never see this, we can change it any way that is wanted. So, host without brackets?Yes, but see below...
Yes, and with #ifdef CONFIG_KVM :). That way the TCG behavior stays untouched.
"host" only makes sense for KVM, not for TCG. So we would need one other placeholder model for libvirt.see my reply to Alex' comment: the placeholder name must be chosen carefully, i.e. future-proofOn further thoughts, didn't we discuss that the issue libvirt wants to address is that migration from z10 to z9 must fail? That's not solved with -cpu host, we would need two other models then. IMO ideally -cpu host should have the same semantics as on x86, that is passing the host features through mostly 1:1. IIUC there is currently no way to not do so?
That is another problem that we need to solve, but one thing at a time.
What about future-wise having -cpu host not be a subclass and instead behaving like Alex' -cpu best, given the above semantics? What I am just worried about with this patch is cementing the use of -cpu host into libvirt when that is not a mid-term solution.
I think on s390 we can get away with the same method as ppc for -cpu host, which basically is -cpu best without fuzziness.
Alex
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