Tim Deegan
2010-Feb-16 17:43 UTC
[Xen-devel] AMD extended migration CPU masks: why only on CPU 0?
Hi Travis, In c/s 18402, the CPUID masks are only set once, on CPU 0. Can you explain why this doesn''t have to happen on every core, or at least every socket? The white paper doesn''t discuss it. Cheers, Tim. -- Tim Deegan <Tim.Deegan@citrix.com> Principal Software Engineer, XenServer Engineering Citrix Systems UK Ltd. (Company #02937203, SL9 0BG) _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Wei Huang
2010-Feb-19 20:27 UTC
Re: [Xen-devel] AMD extended migration CPU masks: why only on CPU 0?
Tim, The (extended) CPUID mask MSRs are associated with each core. They need to be updated on each core if migration happens across CPUs. Changset 18402 does update the MSRs for each core. But printk() only happens on core 0. If you move printk() statements below wrmsr(), you will see it been called on each core. It is hard to justify which way is better. I attach the patch anyway, in case Keir or you want it for xen-unstable. Signed-off-by: Wei Huang <wei.huang2@amd.com> Best, -Wei Tim Deegan wrote:> Hi Travis, > > In c/s 18402, the CPUID masks are only set once, on CPU 0. Can you > explain why this doesn''t have to happen on every core, or at least every > socket? The white paper doesn''t discuss it. > > Cheers, > > Tim. > >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Tim Deegan
2010-Feb-22 13:36 UTC
Re: [Xen-devel] AMD extended migration CPU masks: why only on CPU 0?
Hi, At 20:27 +0000 on 19 Feb (1266611232), Wei Huang wrote:> The (extended) CPUID mask MSRs are associated with each core. They need > to be updated on each core if migration happens across CPUs. Changset > 18402 does update the MSRs for each core.Oh, so it does. :) My mistake; sorry for the noise. Cheers, Tim. -- Tim Deegan <Tim.Deegan@citrix.com> Principal Software Engineer, XenServer Engineering Citrix Systems UK Ltd. (Company #02937203, SL9 0BG) _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel