>From efdfbd66b4f0ff6f005f9d30891adb8bd3f3eefa Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Mon, 10 Jun 2013 16:48:09 -0400 Subject: [PATCH] xen/pci: Deal with toolstack missing an 'XenbusStateClosing'. There are two tool-stack that can instruct the Xen PCI frontend and backend to change states: 'xm' (Python code with a daemon), and 'xl' (C library - does not keep state changes). With the 'xm', the path to disconnect a PCI device (xm pci-detach )is: 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)-> 4(Connected)->5(Closing*). The * is for states that the tool-stack sets. For 'xl', it is similar: 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)-> 4(Connected) Both of them also tear down the XenBus structure, so the backend state ends up going in the 3(Initialised) and calls pcifront_xenbus_remove. When a PCI device is plugged in (xm pci-attach ) both of them follow the same pattern: 2(InitWait*), 3(Initialized*), 4(Connected*)->4(Connected). [xen-pcifront ignores the 2,3 state changes and only acts when 4 (Connected) has been reached] The problem is that git commit 3d925320e9e2de162bd138bf97816bda8c3f71be ("xen/pcifront: Use Xen-SWIOTLB when initting if required") introduced a mechanism to initialize the SWIOTLB when the Xen PCI front moves to Connected state. It also had some aggressive seatbelt code check that would warn the user if one tried to change to Connected state without hitting first the Closing state: pcifront pci-0: PCI frontend already installed! However, that code can be relaxed and we can continue on working even if the frontend is instructed to be the 'Connected' state with no devices and then gets tickled to be in 'Connected' state again. In other words, this 4(Connected)->5(Closing)->4(Connected) state was expected, while 4(Connected)->.... anything but 5(Closing)->4(Connected) was not. This patch removes that aggressive check and allows Xen pcifront to work with the 'xl' toolstack. Cc: Bjorn Helgaas Cc: linux-pci@vger.kernel.org Cc: stable@vger.kernel.org Signed-off-by: Konrad Rzeszutek Wilk --- drivers/pci/xen-pcifront.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c index ac99515..cc46e253 100644 --- a/drivers/pci/xen-pcifront.c +++ b/drivers/pci/xen-pcifront.c @@ -675,10 +675,9 @@ static int pcifront_connect_and_init_dma(struct pcifront_device *pdev) if (!pcifront_dev) { dev_info(&pdev->xdev->dev, "Installing PCI frontend\n"); pcifront_dev = pdev; - } else { - dev_err(&pdev->xdev->dev, "PCI frontend already installed!\n"); + } else err = -EEXIST; - } + spin_unlock(&pcifront_dev_lock); if (!err && !swiotlb_nr_tbl()) { @@ -846,7 +845,7 @@ static int pcifront_try_connect(struct pcifront_device *pdev) goto out; err = pcifront_connect_and_init_dma(pdev); - if (err) { + if (err && err != -EEXIST) { xenbus_dev_fatal(pdev->xdev, err, "Error setting up PCI Frontend"); goto out; -- 1.8.1.4