linux-kernel - Re: [PATCH] PCI: pciehp: Fix system hang on resume after hot-unplug during suspend

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Message-ID: <ZvvXDQSBRZMEI2EX@wunner.de>
Date: Tue, 1 Oct 2024 13:03:41 +0200
From: Lukas Wunner <lukas@...ner.de>
To: AceLan Kao <acelan.kao@...onical.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: pciehp: Fix system hang on resume after hot-unplug
 during suspend

On Tue, Oct 01, 2024 at 01:02:46PM +0200, Lukas Wunner wrote:
> On Mon, Sep 30, 2024 at 09:31:53AM +0800, AceLan Kao wrote:
> > Lukas Wunner <lukas@...ner.de> 2024 9 28 8:51:
> > > -       if (pci_get_dsn(pdev) != ctrl->dsn)
> > > +       dsn = pci_get_dsn(pdev);
> > > +       if (!PCI_POSSIBLE_ERROR(dsn) &&
> > > +           dsn != ctrl->dsn)
> > >                 return true;
> > 
> > In my case, the pciehp_device_replaced() returns true from this final check.
> > And these are the values I got
> > dsn = 0x00000000, ctrl->dsn = 0x7800AA00
> > dsn = 0x00000000, ctrl->dsn = 0x21B7D000
> 
> Ah because pci_get_dsn() returns 0 if the device is gone.
> Below is a modified patch which returns false in that case.

Sorry, forgot to include the patch:

-- >8 --

diff --git a/drivers/pci/hotplug/pciehp_core.c b/drivers/pci/hotplug/pciehp_core.c
index ff458e6..957c320 100644
--- a/drivers/pci/hotplug/pciehp_core.c
+++ b/drivers/pci/hotplug/pciehp_core.c
@@ -287,24 +287,32 @@ static int pciehp_suspend(struct pcie_device *dev)
 static bool pciehp_device_replaced(struct controller *ctrl)
 {
 	struct pci_dev *pdev __free(pci_dev_put);
+	u64 dsn;
 	u32 reg;
 
 	pdev = pci_get_slot(ctrl->pcie->port->subordinate, PCI_DEVFN(0, 0));
 	if (!pdev)
+		return false;
+
+	if (pci_read_config_dword(pdev, PCI_VENDOR_ID, &reg) == 0 &&
+	    !PCI_POSSIBLE_ERROR(reg) &&
+	    reg != (pdev->vendor | (pdev->device << 16)))
 		return true;
 
-	if (pci_read_config_dword(pdev, PCI_VENDOR_ID, &reg) ||
-	    reg != (pdev->vendor | (pdev->device << 16)) ||
-	    pci_read_config_dword(pdev, PCI_CLASS_REVISION, &reg) ||
+	if (pci_read_config_dword(pdev, PCI_CLASS_REVISION, &reg) == 0 &&
+	    !PCI_POSSIBLE_ERROR(reg) &&
 	    reg != (pdev->revision | (pdev->class << 8)))
 		return true;
 
 	if (pdev->hdr_type == PCI_HEADER_TYPE_NORMAL &&
-	    (pci_read_config_dword(pdev, PCI_SUBSYSTEM_VENDOR_ID, &reg) ||
-	     reg != (pdev->subsystem_vendor | (pdev->subsystem_device << 16))))
+	    pci_read_config_dword(pdev, PCI_SUBSYSTEM_VENDOR_ID, &reg) == 0 &&
+	    !PCI_POSSIBLE_ERROR(reg) &&
+	    reg != (pdev->subsystem_vendor | (pdev->subsystem_device << 16)))
 		return true;
 
-	if (pci_get_dsn(pdev) != ctrl->dsn)
+	if ((dsn = pci_get_dsn(pdev)) &&
+	    !PCI_POSSIBLE_ERROR(dsn) &&
+	    dsn != ctrl->dsn)
 		return true;
 
 	return false;