Messages in this thread | | | Subject | Re: [Xen-devel] [PATCH] xen/x86: Update topology map for PV VCPUs | From | David Vrabel <> | Date | Thu, 6 Oct 2016 15:12:04 +0100 |
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On 05/10/16 18:09, Boris Ostrovsky wrote: > Early during boot topology_update_package_map() computes > logical_pkg_ids for all present processors. > > Later, when processors are brought up, identify_cpu() updates > these values based on phys_pkg_id which is a function of > initial_apicid. On PV guests the latter may point to a > non-existing node, causing logical_pkg_ids to be set to -1. > > Intel's RAPL uses logical_pkg_id (as topology_logical_package_id()) > to index its arrays and therefore in this case will point to index > 65535 (since logical_pkg_id is a u16). This could lead to either a > crash or may actually access random memory location. > > As a workaround, we recompute topology during CPU bringup to reset > logical_pkg_id to a valid value. > > (The reason for initial_apicid being bogus is because it is > initial_apicid of the processor from which the guest is launched. > This value is CPUID(1).EBX[31:24])
Applied to for-linus-4.9, thanks.
David
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