linux-kernel - Re: [PATCH] xen: Add support for XenServer 6.1 platform device

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Message-ID: <20250225175044.GA511149@bhelgaas>
Date: Tue, 25 Feb 2025 11:50:44 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Frediano Ziglio <frediano.ziglio@...ud.com>
Cc: xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, Juergen Gross <jgross@...e.com>,
	Stefano Stabellini <sstabellini@...nel.org>,
	Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH] xen: Add support for XenServer 6.1 platform device

On Tue, Feb 25, 2025 at 02:03:53PM +0000, Frediano Ziglio wrote:
> On XenServer on Windows machine a platform device with ID 2 instead of
> 1 is used.
> This device is mainly identical to device 1 but due to some Windows
> update behaviour it was decided to use a device with a different ID.
> This causes compatibility issues with Linux which expects, if Xen
> is detected, to find a Xen platform device (5853:0001) otherwise code
> will crash due to some missing initialization (specifically grant
> tables).
> The device 2 is presented by Xapi adding device specification to
> Qemu command line.

Add blank lines between paragraphs.

A crash seems unfortunate.  And it sounds like a user mistake, e.g., a
typo in the Qemu device specification, could also cause a crash?

If the crash is distinctive, a hint here like a dmesg line or two
might help users.

> Signed-off-by: Frediano Ziglio <frediano.ziglio@...ud.com>
> ---
>  drivers/xen/platform-pci.c | 2 ++
>  include/linux/pci_ids.h    | 1 +
>  2 files changed, 3 insertions(+)
> 
> diff --git a/drivers/xen/platform-pci.c b/drivers/xen/platform-pci.c
> index 544d3f9010b9..9cefc7d6bcba 100644
> --- a/drivers/xen/platform-pci.c
> +++ b/drivers/xen/platform-pci.c
> @@ -174,6 +174,8 @@ static int platform_pci_probe(struct pci_dev *pdev,
>  static const struct pci_device_id platform_pci_tbl[] = {
>  	{PCI_VENDOR_ID_XEN, PCI_DEVICE_ID_XEN_PLATFORM,
>  		PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0},
> +	{PCI_VENDOR_ID_XEN, PCI_DEVICE_ID_XEN_PLATFORM_XS61,
> +		PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0},
>  	{0,}
>  };
>  
> diff --git a/include/linux/pci_ids.h b/include/linux/pci_ids.h
> index 1a2594a38199..e4791fd97ee0 100644
> --- a/include/linux/pci_ids.h
> +++ b/include/linux/pci_ids.h
> @@ -3241,6 +3241,7 @@
>  
>  #define PCI_VENDOR_ID_XEN		0x5853
>  #define PCI_DEVICE_ID_XEN_PLATFORM	0x0001
> +#define PCI_DEVICE_ID_XEN_PLATFORM_XS61	0x0002

If this is the only place PCI_DEVICE_ID_XEN_PLATFORM_XS61 is used, we
would put this in platform-pci.c, per the pci_ids.h comment:

 *      Do not add new entries to this file unless the definitions
 *      are shared between multiple drivers.

>  #define PCI_VENDOR_ID_OCZ		0x1b85
>  
> -- 
> 2.48.1
>