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Re: [Xen-devel] ACPI-Tables corrupted?
On 07/28/2010 02:45 PM, Keir Fraser wrote:
On 28/07/2010 13:13, "Juergen Gross"<juergen.gross@xxxxxxxxxxxxxx> wrote:As Dom0 is a pv-kernel, it should be able to ignore this entry. The crash kernel OTOH should not panic due to the trashed entry! What is the correct solution here?Could provide a cmdline option to not nobble the DMAR?That's a possibility. I wonder whether it wouldn't be better to let dom0 decide not to use it if running under xen. This would remove the requirement for zapping the ACPI table. IMO it's always a bad idea to change data of a deeper layer...If we don't zap the DMAR then every existing dom0 kernel will fail with new hypervisor. We could gate it on a new elfnote, or rename to XMAR and have dom0 rename it back, or just have a flag day.
The really clean solution would be to virtualize the ACPI table for dom0 and remove the DMAR entry in this version. This would require some major work, I guess (clone at least the BIOS page containing the ACPI anchor and present a modified version to dom0).
The crash kernel expects a valid DMAR entry, as following code in enable_IR_x2apic() suggests:I don't know what that function does, nor how the error path below depends on DMAR. DMAR isn't mentioned in the below code.Sorry, here a larger fragment (source arch/x86/kernel/apic/apic.c): /* IR is required if there is APIC ID> 255 even when running * under KVM */ if (max_physical_apicid> 255 || !kvm_para_available()) goto nox2apic;The if stmt is confusing. Also, what would happen if this kernel was booted on a system without VT-d (and hence no DMAR)? Presumably it *can* boot in a DMAR-less environment -- there must be something odd going on for it to end on this path for us.
Yeah, that puzzled me, too. Juergen -- Juergen Gross Principal Developer Operating Systems TSP ES&S SWE OS6 Telephone: +49 (0) 89 3222 2967 Fujitsu Technology Solutions e-mail: juergen.gross@xxxxxxxxxxxxxx Domagkstr. 28 Internet: ts.fujitsu.com D-80807 Muenchen Company details: ts.fujitsu.com/imprint.html _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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