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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
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.)
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