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Re: [PATCH] x86/smp: Factor out parts of native_smp_prepare_cpus()
- To: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
- From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
- Date: Mon, 8 Nov 2021 12:20:26 -0500
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- Delivery-date: Mon, 08 Nov 2021 17:21:45 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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)
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.
Should we re-architect this whole smp_prepare_cpus() thing instead? Have
a common function and a guest function? HyperV for instance seems to
call native_smp_prepare_cpus() and then does something extra (as does
xen_hvm).
Something like
void smp_prepare_cpus()
{
// Code that this patch moved to smp_prepare_cpus_common();
smp_ops.smp_prepare_cpus(); // Including baremetal
}
?
XenHVM and hyperV will need to call native smp_op too. Not sure this will be
prettier than what it is now?
-boris
-boris
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