linux-kernel - Re: [PATCH] PCI/PM: Print the pci config space of devices before suspend

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Date:   Mon, 13 Jan 2020 15:45:10 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     linux-pci@...r.kernel.org, "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI/PM: Print the pci config space of devices before
 suspend

On Mon, Jan 13, 2020 at 02:07:24PM +0800, Chen Yu wrote:
> The pci config space was found to be insane during resume
> from hibernation(S4, or suspend to disk) on a VM:
> 
>  serial 0000:00:16.3: restoring config space at offset 0x14
>  (was 0x9104e000, writing 0xffffffff)
> 
> Either the snapshot on the disk has been scribbled or the pci
> config space becomes invalid before suspend. To narrow down
> and benefit future debugging, print the pci config space
> being saved before suspend, which is symmetric to the log
> in pci_restore_config_dword().
> 
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Len Brown <lenb@...nel.org>
> Cc: linux-pci@...r.kernel.org
> Cc: linux-pm@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Chen Yu <yu.c.chen@...el.com>

Applied to pci/pm for v5.6, thanks!

> ---
>  drivers/pci/pci.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index e87196cc1a7f..34cde70440c3 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1372,8 +1372,11 @@ int pci_save_state(struct pci_dev *dev)
>  {
>  	int i;
>  	/* XXX: 100% dword access ok here? */
> -	for (i = 0; i < 16; i++)
> +	for (i = 0; i < 16; i++) {
>  		pci_read_config_dword(dev, i * 4, &dev->saved_config_space[i]);
> +		pci_dbg(dev, "saving config space at offset %#x (reading %#x)\n",
> +			i * 4, dev->saved_config_space[i]);
> +	}
>  	dev->state_saved = true;
>  
>  	i = pci_save_pcie_state(dev);
> -- 
> 2.17.1
>