linux-kernel - Re: [RFC 2/2] PCI: acpiphp: slowdown hotplug if hotplugging multiple devices at a time

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Date:   Wed, 13 Dec 2023 10:47:34 +0100
From:   Fiona Ebner <f.ebner@...xmox.com>
To:     Igor Mammedov <imammedo@...hat.com>, linux-kernel@...r.kernel.org
Cc:     Dongli Zhang <dongli.zhang@...cle.com>, linux-acpi@...r.kernel.org,
        linux-pci@...r.kernel.org, mst@...hat.com, rafael@...nel.org,
        lenb@...nel.org, bhelgaas@...gle.com,
        mika.westerberg@...ux.intel.com, boris.ostrovsky@...cle.com,
        joe.jin@...cle.com, stable@...r.kernel.org,
        Thomas Lamprecht <t.lamprecht@...xmox.com>
Subject: Re: [RFC 2/2] PCI: acpiphp: slowdown hotplug if hotplugging multiple
 devices at a time

Am 13.12.23 um 01:36 schrieb Igor Mammedov:
> previous commit ("PCI: acpiphp: enable slot only if it hasn't been enabled already"
> introduced a workaround to avoid a race between SCSI_SCAN_ASYNC job and
> bridge reconfiguration in case of single HBA hotplug.
> However in virt environment it's possible to pause machine hotplug several
> HBAs and let machine run. That can hit the same race when 2nd hotplugged
> HBA will start re-configuring bridge.
> Do the same thing as SHPC and throttle down hotplug of 2nd and up
> devices within single hotplug event.
> 
> Signed-off-by: Igor Mammedov <imammedo@...hat.com>

With only the first patch applied, I could reproduce the issue described
here, i.e. pausing the vCPUs while doing multiple hotplugs and this
patch makes that scenario work too:

Tested-by: Fiona Ebner <f.ebner@...xmox.com>