Re: [PATCH for-4.20 v3 0/5] xen/x86: prevent local APIC errors at shutdown

["Roger Pau Monné" <roger.pau@citrix.com>]

On Wed, Feb 12, 2025 at 09:51:16AM +0100, Jan Beulich wrote:
> On 12.02.2025 09:33, Oleksii Kurochko wrote:
> > 
> > On 2/11/25 7:39 PM, Roger Pau Monné wrote:
> >> On Tue, Feb 11, 2025 at 12:02:04PM +0100, Roger Pau Monne wrote:
> >>> Hello,
> >>>
> >>> The following series aims to prevent local APIC errors from stalling the
> >>> shtudown process.  On XenServer testing we have seen reports of AMD
> >>> boxes sporadically getting stuck in a spam of:
> >>>
> >>> APIC error on CPU0: 00(08), Receive accept error
> >>>
> >>> Messages during shutdown, as a result of device interrupts targeting
> >>> CPUs that are offline (and have the local APIC disabled).
> >>>
> >>> First patch strictly solves the issue of shutdown getting stuck, further
> >>> patches aim to quiesce interrupts from all devices (known by Xen) as an
> >>> attempt to prevent a spurious "APIC error on CPU0: 00(00)" plus also
> >>> make kexec more reliable.
> >>>
> >>> Thanks, Roger.
> >>>
> >>> Roger Pau Monne (5):
> >>>    x86/shutdown: offline APs with interrupts disabled on all CPUs
> >>>    x86/irq: drop fixup_irqs() parameters
> >>>    x86/smp: perform disabling on interrupts ahead of AP shutdown
> >>>    x86/pci: disable MSI(-X) on all devices at shutdown
> >>>    x86/iommu: disable interrupts at shutdown
> >> This is now fully reviewed, can I get your opinion (and
> >> release-acked-by) on which patches we should take for 4.20?
> > 
> > If my understanding is correct to unblock shutdown process, it is enough just
> > to have only first patch merged, correct? So the first patch should be merged.
> > 
> > As second patch doesn't have functional changes, IMO, it could be merged to
> > despite of the fact we have Hard code freeze period.
> > 
> > All other patches, I would like to ask additional opinion (as I am an expert in x86),
> > at first glance it looks like an absence of these patches in staging branch will
> > lead only to triggering "Receive accept error" which I believe won't block shutdown
> > process, so these patches could be postponed until 4.21. On other side, if it is
> > low-risk fixes then we could consider to merge them now.

I expect the following patches might make kexec'ing from Xen a bit
more reliable, as the kexec'ed kernel should find an environment with
interrupts from all Xen known devices quiesced.

> I'm not Roger, but as a data point: While I'm uncertain about patch 2, all
> others in this series will very likely be backported anyway.

I plan to backport the series to the XenServer patch queue also when it
goes in.

Thanks, Roger.