[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Re: breakage with c/s 19950
>>> Christoph Egger <Christoph.Egger@xxxxxxx> 21.07.09 16:49 >>> >In c/s 19950, you disable the GART TLB walk error of the northbridge >as a workaround for AMD K8 CPUs. The comment says, it happens with IOMMU & >3ware & Cerberus. > >There's a Linux/Dom0 boot problem with this: > >The Linux/Dom0 kernel also has this workaround which leads to a #GP in the >guest because in Xen mce.c:mce_wrmsr() returns -1. > >The question is, is the workaround really really necessary ? >IOMMU is not yet on market and if there will be AMD K8 machines with >an IOMMU is very questionable. The code has been in Linux for quite some time, and given it relates to K8 *and* disables some GART functionality I'd suppose the IOMMU talked about here is the old GART one, not the not-yet-on-the-market-one. >If the workaround is not needed, please remove it from both Linux and Xen. >If the workaround is valid, then mce.c:mce_wrmsr() needs a special check >for this workaround to NOT return -1. I'd rather say this handling is supposed to happen only in the hypervisor, i.e. Dom0 should not even try to do it (which would, without mce_wrmsr(), have no effect anyway due to the white-listing of MSRs being writable by domains). Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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