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Message-ID: <ee16518a-69a6-d3bc-2581-61b37b803af8@suse.com>
Date: Thu, 6 Oct 2022 07:12:08 +0200
From: Juergen Gross <jgross@...e.com>
To: Jason Andryuk <jandryuk@...il.com>,
Stefano Stabellini <sstabellini@...nel.org>,
Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
Bjorn Helgaas <bhelgaas@...gle.com>
Cc: xen-devel@...ts.xenproject.org, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xen-pcifront: Handle missed Connected state
On 29.08.22 17:15, Jason Andryuk wrote:
> An HVM guest with linux stubdom and 2 PCI devices failed to start as
> libxl timed out waiting for the PCI devices to be added. It happens
> intermittently but with some regularity. libxl wrote the two xenstore
> entries for the devices, but then timed out waiting for backend state 4
> (Connected) - the state stayed at 7 (Reconfiguring). (PCI passthrough
> to an HVM with stubdomain is PV passthrough to the stubdomain and then
> HVM passthrough with the QEMU inside the stubdomain.)
>
> The stubdom kernel never printed "pcifront pci-0: Installing PCI
> frontend", so it seems to have missed state 4 which would have
> called pcifront_try_connect -> pcifront_connect_and_init_dma
>
> Have pcifront_detach_devices special-case state Initialised and call
> pcifront_connect_and_init_dma. Don't use pcifront_try_connect because
> that sets the xenbus state which may throw off the backend. After
> connecting, skip the remainder of detach_devices since none have been
> initialized yet. When the backend switches to Reconfigured,
> pcifront_attach_devices will pick them up again.
>
> Signed-off-by: Jason Andryuk <jandryuk@...il.com>
Pushed to xen/tip.git for-linus-6.1
Juergen
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