linux-kernel - [PATCH v2] xen: Add support for XenServer 6.1 platform device

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Message-ID: <20250227145016.25350-1-frediano.ziglio@cloud.com>
Date: Thu, 27 Feb 2025 14:50:15 +0000
From: Frediano Ziglio <frediano.ziglio@...ud.com>
To: xen-devel@...ts.xenproject.org,
	linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org
Cc: Frediano Ziglio <frediano.ziglio@...ud.com>,
	"Juergen Gross" <jgross@...e.com>,
	"Stefano Stabellini" <sstabellini@...nel.org>,
	"Oleksandr Tyshchenko" <oleksandr_tyshchenko@...m.com>,
	"Bjorn Helgaas" <bhelgaas@...gle.com>
Subject: [PATCH v2] xen: Add support for XenServer 6.1 platform device

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). Specifically from dmesg

    RIP: 0010:gnttab_expand+0x29/0x210
    Code: 90 0f 1f 44 00 00 55 31 d2 48 89 e5 41 57 41 56 41 55 41 89 fd
          41 54 53 48 83 ec 10 48 8b 05 7e 9a 49 02 44 8b 35 a7 9a 49 02
          <8b> 48 04 8d 44 39 ff f7 f1 45 8d 24 06 89 c3 e8 43 fe ff ff
          44 39
    RSP: 0000:ffffba34c01fbc88 EFLAGS: 00010086
    ...

The device 2 is presented by Xapi adding device specification to
Qemu command line.

Signed-off-by: Frediano Ziglio <frediano.ziglio@...ud.com>
---
 drivers/xen/platform-pci.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/xen/platform-pci.c b/drivers/xen/platform-pci.c
index 544d3f9010b9..1db82da56db6 100644
--- a/drivers/xen/platform-pci.c
+++ b/drivers/xen/platform-pci.c
@@ -26,6 +26,8 @@
 
 #define DRV_NAME    "xen-platform-pci"
 
+#define PCI_DEVICE_ID_XEN_PLATFORM_XS61	0x0002
+
 static unsigned long platform_mmio;
 static unsigned long platform_mmio_alloc;
 static unsigned long platform_mmiolen;
@@ -174,6 +176,8 @@ 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,}
 };
 
-- 
2.48.1