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Date: Fri, 14 Oct 2016 14:54:56 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Boris Ostrovsky <boris.ostrovsky@...cle.com>, David Vrabel <david.vrabel@...rix.com> Subject: [PATCH 4.7 12/31] xen/x86: Update topology map for PV VCPUs 4.7-stable review patch. If anyone has any objections, please let me know. ------------------ From: Boris Ostrovsky <boris.ostrovsky@...cle.com> commit a6a198bc60e6c980a56eca24d33dc7f29139f8ea upstream. 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]) Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com> Signed-off-by: David Vrabel <david.vrabel@...rix.com> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- arch/x86/xen/smp.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/arch/x86/xen/smp.c +++ b/arch/x86/xen/smp.c @@ -87,6 +87,12 @@ static void cpu_bringup(void) cpu_data(cpu).x86_max_cores = 1; set_cpu_sibling_map(cpu); + /* + * identify_cpu() may have set logical_pkg_id to -1 due + * to incorrect phys_proc_id. Let's re-comupte it. + */ + topology_update_package_map(apic->cpu_present_to_apicid(cpu), cpu); + xen_setup_cpu_clockevents(); notify_cpu_starting(cpu);
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