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[Xen-devel] Re: [PATCH] xen: drop anti-dependency on X86_VISWS
- To: Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>
- From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
- Date: Fri, 08 Apr 2011 08:25:50 -0700
- Cc: "randy.dunlap@xxxxxxxxxx" <randy.dunlap@xxxxxxxxxx>, Jeremy Fitzhardinge <Jeremy.Fitzhardinge@xxxxxxxxxx>, "eric.dumazet@xxxxxxxxx" <eric.dumazet@xxxxxxxxx>, "konrad.wilk@xxxxxxxxxx" <konrad.wilk@xxxxxxxxxx>, David Miller <davem@xxxxxxxxxxxxx>, "mirq-linux@xxxxxxxxxxxx" <mirq-linux@xxxxxxxxxxxx>, "mingo@xxxxxxxxxx" <mingo@xxxxxxxxxx>, "hpa@xxxxxxxxx" <hpa@xxxxxxxxx>, "tglx@xxxxxxxxxxxxx" <tglx@xxxxxxxxxxxxx>, "virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx" <virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx>, "pazke@xxxxxxxxx" <pazke@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
- Delivery-date: Fri, 08 Apr 2011 08:26:27 -0700
- List-id: Xen developer discussion <xen-devel.lists.xensource.com>
On 04/07/2011 11:38 PM, Ian Campbell wrote:
>> Not really. The TSC register is a requirement, but that's going to be
>> present on any CPU which can boot Xen. We don't need any of the
>> kernel's TSC machinery though.
> So why the Kconfig dependency then? In principal a kernel compiled for a
> non-TSC processor (which meets the other requirements for Xen, such as
> PAE support) will run just fine under Xen on a newer piece of hardware.
Not sure where it came from. It was probably never needed, or just
added for some secondary effect we wanted.
> Is there any downside to this patch (is X86_CMPXCHG in the same sort of
> boat?)
Only if we don't use cmpxchg in shared memory with other domains or the
hypervisor. (I don't think it will dynamically switch between real and
emulated cmpxchg depending on availability.)
J
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