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Re: [Qemu-devel] [PATCH] Introduce -accel command option.
From: |
Alexander Graf |
Subject: |
Re: [Qemu-devel] [PATCH] Introduce -accel command option. |
Date: |
Tue, 16 Nov 2010 18:32:13 +0100 |
On 16.11.2010, at 18:27, Anthony Liguori wrote:
> On 11/16/2010 11:24 AM, Alexander Graf wrote:
>> On 16.11.2010, at 18:20, Anthony Liguori wrote:
>>
>>
>>> On 11/16/2010 10:59 AM, Alexander Graf wrote:
>>>
>>>>
>>>>> Surely, only if it is running on a Xen Dom0. If you use -M xenpv on a KVM
>>>>> host, then -M xenpv should imply -machine accel=kvm (ie it would be using
>>>>> xenner)
>>>>>
>>>>>
>>>> Actually, it should imply -machine accel=kvm,tcg :). Accelerators really
>>>> are not a machine property. In an ideal world, -M pc would just work with
>>>> xen hvm if -accel xen is given.
>>>>
>>>>
>>> No, an accelerator is both a CPU selection and a machine characteristic.
>>> For KVM, we overload -cpu to modify both the KVM CPU and the TCG CPU both
>>> this won't work with accel=xen. We probably shouldn't do this with KVM
>>> either because there's a significant different between trying to do cpuid
>>> masking with KVM and modifying the TCG cpu emulation support.
>>>
>>> Both KVM and Xen have other impacts on the platform devices though. KVM
>>> does not support SMM so it disables that in the i440fx. KVM prefers to use
>>> it's own in-kernel local APIC (and IOAPIC). That makes it a property of
>>> the machine.
>>>
>> So you're saying the machine should define an accel mask of accels it
>> supports?
>>
>> However all this ends up internally, giving the user an easy option to
>> choose accels would still be nice. Users don't use -device or -machine. They
>> want shortcuts :).
>>
>
> User's want things to just work.
>
> That's why -M xenpv should imply -machine accel=xen.
No, it should imply -machine accel=xen,kvm,tcg. Which should be the default
anyways. For machines that don't work with specific accels, I'd agree that a
machine should be able to mask those out. But in general, we'll always get back
to defaulting to xen,kvm,tcg.
> A user should never have to specify and accelerator option IMHO.
If things don't work out, he should be able to do things like -no-kvm for bug
hunting. In normal use cases, I tend to agree. Things should just work
automatically.
Alex
- [Qemu-devel] [PATCH] Introduce -accel command option., anthony . perard, 2010/11/15
- Re: [Qemu-devel] [PATCH] Introduce -accel command option., Anthony Liguori, 2010/11/15
- Re: [Qemu-devel] [PATCH] Introduce -accel command option., Anthony PERARD, 2010/11/16
- Re: [Qemu-devel] [PATCH] Introduce -accel command option., Anthony Liguori, 2010/11/16
- Re: [Qemu-devel] [PATCH] Introduce -accel command option., Daniel P. Berrange, 2010/11/16
- Re: [Qemu-devel] [PATCH] Introduce -accel command option., Alexander Graf, 2010/11/16
- Re: [Qemu-devel] [PATCH] Introduce -accel command option., Anthony Liguori, 2010/11/16
- Re: [Qemu-devel] [PATCH] Introduce -accel command option., Alexander Graf, 2010/11/16
- Re: [Qemu-devel] [PATCH] Introduce -accel command option., Anthony Liguori, 2010/11/16
- Re: [Qemu-devel] [PATCH] Introduce -accel command option.,
Alexander Graf <=
- Re: [Qemu-devel] [PATCH] Introduce -accel command option., Anthony PERARD, 2010/11/16
- Re: [Qemu-devel] [PATCH] Introduce -accel command option., Alexander Graf, 2010/11/16
- Re: [Qemu-devel] [PATCH] Introduce -accel command option., Anthony Liguori, 2010/11/16
- Re: [Qemu-devel] [PATCH] Introduce -accel command option., Anthony Liguori, 2010/11/16