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From:   Rich Persaud <persaur@gmail.com>
Mime-Version: 1.0 (1.0)
Subject: Re: [PATCH] xen-pcifront: Handle missed Connected state
Date:   Wed, 31 Aug 2022 22:35:06 -0400
Message-Id: <31F127F6-A096-4991-9D4C-1B2E032689A1@gmail.com>
References: <20220829151536.8578-1-jandryuk@gmail.com>
Cc:     Juergen Gross <jgross@suse.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Oleksandr Tyshchenko <Oleksandr_Tyshchenko@epam.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        xen-devel@lists.xenproject.org, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org
In-Reply-To: <20220829151536.8578-1-jandryuk@gmail.com>
To:     Jason Andryuk <jandryuk@gmail.com>
Precedence: bulk

On Aug 29, 2022, at 11:16 AM, Jason Andryuk <jandryuk@gmail.com> wrote:
>=20
> =EF=BB=BFAn 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.)
>=20
> 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

Is there a state machine doc/flowchart for LibXL and Xen PCI device passthro=
ugh to Linux? This would be a valuable addition to Xen's developer docs, eve=
n as a whiteboard photo in this thread.

Rich=