On Mon, Nov 08, 2021 at 12:20:26PM -0500, Boris Ostrovsky wrote:
On 11/8/21 10:11 AM, Peter Zijlstra wrote:
On Tue, Nov 02, 2021 at 07:36:36PM -0400, Boris Ostrovsky wrote:
Commit 66558b730f25 ("sched: Add cluster scheduler level for x86")
introduced cpu_l2c_shared_map mask which is expected to be initialized
by smp_op.smp_prepare_cpus(). That commit only updated
native_smp_prepare_cpus() version but not xen_pv_smp_prepare_cpus().
As result Xen PV guests crash in set_cpu_sibling_map().
While the new mask can be allocated in xen_pv_smp_prepare_cpus() one can
see that both versions of smp_prepare_cpus ops share a number of common
operations that can be factored out. So do that instead.
Fixes: 66558b730f25 ("sched: Add cluster scheduler level for x86")
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Thanks! I'll go stick that somewhere /urgent (I've had another report on
that here:
https://lkml.kernel.org/r/20211105074139.GE174703@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
)
Thank you. (I don't see this message btw)
Urgh, that thread never went to lkml :/
But looking at those functions; there seems to be more spurious
differences. For example, the whole sched_topology thing.
I did look at that and thought this should be benign given that Xen PV
is not really topology-aware. I didn't see anything that would be a
cause for concern but perhaps you can point me to things I missed.
And me not being Xen aware... What does Xen-PV guests see of the CPUID
topology fields? Does it fully sanitize the CPUID data, or is it a clean
pass-through from whatever CPU the vCPU happens to run on at the time?
