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virtio_pci: modern driver

RFC PATCH In review Michael S. Tsirkin 2 participants 10 messages Dec 11, 2014

Subsystems (5)
PCI Library code Generic include/asm header files virtio core +1 more subsystems
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Michael S. Tsirkin

author maintainer
#0 lore raw

cover virtio_pci: modern driver

Based on Rusty's patches.
Coding style and funny jokes are his.
Bugs and a star wars reference (should be easy to spot) are mine. Untested, but useful as basis for beginning the qemu work.

TODO:
= simplify probing: use a common probe function, probe with modern driver
first, if that fails - probe with legacy driver.
BUGS: ATM legacy driver can win and drive a transitional device
Until this is fixed, to test, disable transitional mode in device

More ideas (optional):
= allow disabling legacy driver
= support shared IRQ for config, read ISR
= allocate VQ ring in chunks, good for large rings
= use less meory for small VQ ring in chunks, good for large rings

General TODOs:
= add config generation support
= move alloc_virtqueue_pages to virtio core, reuse in e.g. ccw

Michael S Tsirkin (1):
pci: add pci_iomap_range

Michael S. Tsirkin (2):
virtio_pci: add VIRTIO_PCI_NO_LEGACY
virtio_pci: modern driver

Rusty Russell (2):
virtio-pci: define layout for virtio 1.0
virtio_pci: macros for PCI layout offsets.

 drivers/virtio/virtio_pci_common.h |  23 +-
 include/asm-generic/pci_iomap.h    |   5 +
 include/uapi/linux/virtio_pci.h    | 106 ++++++-
 drivers/virtio/virtio_pci_modern.c | 621 +++++++++++++++++++++++++++++++++++++
 lib/pci_iomap.c                    |  46 ++-
 drivers/virtio/Makefile            |   2 +-
 6 files changed, 788 insertions(+), 15 deletions(-)
 create mode 100644 drivers/virtio/virtio_pci_modern.c
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author maintainer
#1 lore raw

RFC PATCH 1/5 virtio_pci: add VIRTIO_PCI_NO_LEGACY

Add macro to disable all legacy register defines.
Helpful to make sure legacy macros don't leak
through into modern code.

Signed-off-by Michael S. Tsirkin <[email protected]>
---
 include/uapi/linux/virtio_pci.h | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)
include/uapi/linux/virtio_pci.h +10 -5
index e5ec1ca..35b552c 100644
@@ -41,6 +41,8 @@
 
 #include <linux/virtio_config.h>
 
+#ifndef VIRTIO_PCI_NO_LEGACY
+
 /* A 32-bit r/o bitmask of the features supported by the host */
 #define VIRTIO_PCI_HOST_FEATURES	0
 

@@ -67,16 +69,11 @@
  * a read-and-acknowledge. */
 #define VIRTIO_PCI_ISR			19
 
-/* The bit of the ISR which indicates a device configuration change. */
-#define VIRTIO_PCI_ISR_CONFIG		0x2
-
 /* MSI-X registers: only enabled if MSI-X is enabled. */
 /* A 16-bit vector for configuration changes. */
 #define VIRTIO_MSI_CONFIG_VECTOR        20
 /* A 16-bit vector for selected queue notifications. */
 #define VIRTIO_MSI_QUEUE_VECTOR         22
-/* Vector value used to disable MSI for queue */
-#define VIRTIO_MSI_NO_VECTOR            0xffff
 
 /* The remaining space is defined by each driver as the per-driver
  * configuration space */

@@ -94,4 +91,12 @@
 /* The alignment to use between consumer and producer parts of vring.
  * x86 pagesize again. */
 #define VIRTIO_PCI_VRING_ALIGN		4096
+
+#endif /* VIRTIO_PCI_NO_LEGACY */
+
+/* The bit of the ISR which indicates a device configuration change. */
+#define VIRTIO_PCI_ISR_CONFIG		0x2
+/* Vector value used to disable MSI for queue */
+#define VIRTIO_MSI_NO_VECTOR            0xffff
+
 #endif
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author maintainer
#2 lore raw

RFC PATCH 2/5 virtio-pci: define layout for virtio 1.0

In reply to Michael S. Tsirkin

From: Rusty Russell <[email protected]>

Based on patches by Michael S. Tsirkin <[email protected]>, but I found it hard to follow so changed to use structures which are more self-documenting.

Signed-off-by Rusty Russell <[email protected]>
Signed-off-by Michael S. Tsirkin <[email protected]>
---
 include/uapi/linux/virtio_pci.h | 62 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
include/uapi/linux/virtio_pci.h +62 -0
index 35b552c..8423764 100644
@@ -99,4 +99,66 @@
 /* Vector value used to disable MSI for queue */
 #define VIRTIO_MSI_NO_VECTOR            0xffff
 
+#ifndef VIRTIO_PCI_NO_MODERN
+
+/* IDs for different capabilities.  Must all exist. */
+
+/* Common configuration */
+#define VIRTIO_PCI_CAP_COMMON_CFG	1
+/* Notifications */
+#define VIRTIO_PCI_CAP_NOTIFY_CFG	2
+/* ISR access */
+#define VIRTIO_PCI_CAP_ISR_CFG		3
+/* Device specific confiuration */
+#define VIRTIO_PCI_CAP_DEVICE_CFG	4
+
+/* This is the PCI capability header: */
+struct virtio_pci_cap {
+	__u8 cap_vndr;		/* Generic PCI field: PCI_CAP_ID_VNDR */
+	__u8 cap_next;		/* Generic PCI field: next ptr. */
+	__u8 cap_len;		/* Generic PCI field: capability length */
+	__u8 type_and_bar;	/* Upper 3 bits: bar.
+				 * Lower 3 is VIRTIO_PCI_CAP_*_CFG. */
+	__le32 offset;		/* Offset within bar. */
+	__le32 length;		/* Length. */
+};
+
+#define VIRTIO_PCI_CAP_BAR_SHIFT	5
+#define VIRTIO_PCI_CAP_BAR_MASK		0x7
+#define VIRTIO_PCI_CAP_TYPE_SHIFT	0
+#define VIRTIO_PCI_CAP_TYPE_MASK	0x7
+
+struct virtio_pci_notify_cap {
+	struct virtio_pci_cap cap;
+	__le32 notify_off_multiplier;	/* Multiplier for queue_notify_off. */
+};
+
+/* Fields in VIRTIO_PCI_CAP_COMMON_CFG: */
+struct virtio_pci_common_cfg {
+	/* About the whole device. */
+	__le32 device_feature_select;	/* read-write */
+	__le32 device_feature;		/* read-only */
+	__le32 guest_feature_select;	/* read-write */
+	__le32 guest_feature;		/* read-write */
+	__le16 msix_config;		/* read-write */
+	__le16 num_queues;		/* read-only */
+	__u8 device_status;		/* read-write */
+	__u8 unused1;
+
+	/* About a specific virtqueue. */
+	__le16 queue_select;		/* read-write */
+	__le16 queue_size;		/* read-write, power of 2. */
+	__le16 queue_msix_vector;	/* read-write */
+	__le16 queue_enable;		/* read-write */
+	__le16 queue_notify_off;	/* read-only */
+	__le32 queue_desc_lo;		/* read-write */
+	__le32 queue_desc_hi;		/* read-write */
+	__le32 queue_avail_lo;		/* read-write */
+	__le32 queue_avail_hi;		/* read-write */
+	__le32 queue_used_lo;		/* read-write */
+	__le32 queue_used_hi;		/* read-write */
+};
+
+#endif /* VIRTIO_PCI_NO_MODERN */
+
 #endif
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author maintainer
#3 lore raw

RFC PATCH 2/5 virtio-pci: define layout for virtio 1.0

In reply to Michael S. Tsirkin

From: Rusty Russell <[email protected]>

Based on patches by Michael S. Tsirkin <[email protected]>, but I found it hard to follow so changed to use structures which are more self-documenting.

Signed-off-by Rusty Russell <[email protected]>
Signed-off-by Michael S. Tsirkin <[email protected]>
---
 include/uapi/linux/virtio_pci.h | 62 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
include/uapi/linux/virtio_pci.h +62 -0
index 35b552c..8423764 100644
@@ -99,4 +99,66 @@
 /* Vector value used to disable MSI for queue */
 #define VIRTIO_MSI_NO_VECTOR            0xffff
 
+#ifndef VIRTIO_PCI_NO_MODERN
+
+/* IDs for different capabilities.  Must all exist. */
+
+/* Common configuration */
+#define VIRTIO_PCI_CAP_COMMON_CFG	1
+/* Notifications */
+#define VIRTIO_PCI_CAP_NOTIFY_CFG	2
+/* ISR access */
+#define VIRTIO_PCI_CAP_ISR_CFG		3
+/* Device specific confiuration */
+#define VIRTIO_PCI_CAP_DEVICE_CFG	4
+
+/* This is the PCI capability header: */
+struct virtio_pci_cap {
+	__u8 cap_vndr;		/* Generic PCI field: PCI_CAP_ID_VNDR */
+	__u8 cap_next;		/* Generic PCI field: next ptr. */
+	__u8 cap_len;		/* Generic PCI field: capability length */
+	__u8 type_and_bar;	/* Upper 3 bits: bar.
+				 * Lower 3 is VIRTIO_PCI_CAP_*_CFG. */
+	__le32 offset;		/* Offset within bar. */
+	__le32 length;		/* Length. */
+};
+
+#define VIRTIO_PCI_CAP_BAR_SHIFT	5
+#define VIRTIO_PCI_CAP_BAR_MASK		0x7
+#define VIRTIO_PCI_CAP_TYPE_SHIFT	0
+#define VIRTIO_PCI_CAP_TYPE_MASK	0x7
+
+struct virtio_pci_notify_cap {
+	struct virtio_pci_cap cap;
+	__le32 notify_off_multiplier;	/* Multiplier for queue_notify_off. */
+};
+
+/* Fields in VIRTIO_PCI_CAP_COMMON_CFG: */
+struct virtio_pci_common_cfg {
+	/* About the whole device. */
+	__le32 device_feature_select;	/* read-write */
+	__le32 device_feature;		/* read-only */
+	__le32 guest_feature_select;	/* read-write */
+	__le32 guest_feature;		/* read-write */
+	__le16 msix_config;		/* read-write */
+	__le16 num_queues;		/* read-only */
+	__u8 device_status;		/* read-write */
+	__u8 unused1;
+
+	/* About a specific virtqueue. */
+	__le16 queue_select;		/* read-write */
+	__le16 queue_size;		/* read-write, power of 2. */
+	__le16 queue_msix_vector;	/* read-write */
+	__le16 queue_enable;		/* read-write */
+	__le16 queue_notify_off;	/* read-only */
+	__le32 queue_desc_lo;		/* read-write */
+	__le32 queue_desc_hi;		/* read-write */
+	__le32 queue_avail_lo;		/* read-write */
+	__le32 queue_avail_hi;		/* read-write */
+	__le32 queue_used_lo;		/* read-write */
+	__le32 queue_used_hi;		/* read-write */
+};
+
+#endif /* VIRTIO_PCI_NO_MODERN */
+
 #endif
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author maintainer
#4 lore raw

RFC PATCH 3/5 pci: add pci_iomap_range

In reply to Michael S. Tsirkin

From: Michael S Tsirkin <[email protected]>

Virtio drivers should map the part of the range they need, not necessarily all of it. They also need non-cacheable mapping even for prefetchable BARs.

Signed-off-by Michael S. Tsirkin <[email protected]>
Signed-off-by Rusty Russell <[email protected]>
---
 include/asm-generic/pci_iomap.h |  5 +++++
 lib/pci_iomap.c                 | 46 +++++++++++++++++++++++++++++++++++------
 2 files changed, 45 insertions(+), 6 deletions(-)
include/asm-generic/pci_iomap.h +5 -0
index ce37349..8777331 100644
@@ -15,6 +15,11 @@ struct pci_dev;
 #ifdef CONFIG_PCI
 /* Create a virtual mapping cookie for a PCI BAR (memory or IO) */
 extern void __iomem *pci_iomap(struct pci_dev *dev, int bar, unsigned long max);
+extern void __iomem *pci_iomap_range(struct pci_dev *dev, int bar,
+				     unsigned offset,
+				     unsigned long minlen,
+				     unsigned long maxlen,
+				     bool force_nocache);
 /* Create a virtual mapping cookie for a port on a given PCI device.
  * Do not call this directly, it exists to make it easier for architectures
  * to override */
lib/pci_iomap.c +40 -6

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#5 lore raw

Re: [PATCH RFC 3/5] pci: add pci_iomap_range

lib/pci_iomap.c line 56

Quoted 7 lines · On Thursday 11 December 2014 21:37:34 Michael S. Tsirkin wrote:
        if (flags & IORESOURCE_MEM) {
lib/pci_iomap.c +1 -1
-               if (flags & IORESOURCE_CACHEABLE)
+               if (!force_nocache && (flags & IORESOURCE_CACHEABLE))
                        return ioremap(start, len);
                return ioremap_nocache(start, len);
        }

ioremap is the same as ioremap_nocache, so this doesn't really make any sense. IORESOURCE_CACHEABLE is practically only set for ROM bars, which we rarely map.

Arnd

author maintainer
#6 lore raw

Re: [PATCH RFC 3/5] pci: add pci_iomap_range

Quoted 9 lines · Arnd Bergmann

lib/pci_iomap.c line 56

Quoted 7 lines · On Thursday 11 December 2014 21:37:34 Michael S. Tsirkin wrote:
        if (flags & IORESOURCE_MEM) {
lib/pci_iomap.c +1 -1
-               if (flags & IORESOURCE_CACHEABLE)
+               if (!force_nocache && (flags & IORESOURCE_CACHEABLE))
                        return ioremap(start, len);
                return ioremap_nocache(start, len);
        }
Quoted 5 lines

ioremap is the same as ioremap_nocache, so this doesn't really make any sense. IORESOURCE_CACHEABLE is practically only set for ROM bars, which we rarely map.

Arnd

Hmm I think you are right.
It's an old patch - I think at one point in time we did set it when we now set IORESOURCE_PREFETCH.
I'll drop this parameter.

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#7 lore raw

RFC PATCH 3/5 pci: add pci_iomap_range

In reply to Michael S. Tsirkin

From: Michael S Tsirkin <[email protected]>

Virtio drivers should map the part of the range they need, not necessarily all of it. They also need non-cacheable mapping even for prefetchable BARs.

Signed-off-by Michael S. Tsirkin <[email protected]>
Signed-off-by Rusty Russell <[email protected]>
---
 include/asm-generic/pci_iomap.h |  5 +++++
 lib/pci_iomap.c                 | 46 +++++++++++++++++++++++++++++++++++------
 2 files changed, 45 insertions(+), 6 deletions(-)
include/asm-generic/pci_iomap.h +5 -0
index ce37349..8777331 100644
@@ -15,6 +15,11 @@ struct pci_dev;
 #ifdef CONFIG_PCI
 /* Create a virtual mapping cookie for a PCI BAR (memory or IO) */
 extern void __iomem *pci_iomap(struct pci_dev *dev, int bar, unsigned long max);
+extern void __iomem *pci_iomap_range(struct pci_dev *dev, int bar,
+				     unsigned offset,
+				     unsigned long minlen,
+				     unsigned long maxlen,
+				     bool force_nocache);
 /* Create a virtual mapping cookie for a port on a given PCI device.
  * Do not call this directly, it exists to make it easier for architectures
  * to override */
lib/pci_iomap.c +40 -6

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#8 lore raw

RFC PATCH 4/5 virtio_pci: modern driver

In reply to Michael S. Tsirkin

It compiles! Must be perfect.

Signed-off-by Michael S. Tsirkin <[email protected]>
---
 drivers/virtio/virtio_pci_common.h |  23 +-
 include/uapi/linux/virtio_pci.h    |  29 ++
 drivers/virtio/virtio_pci_modern.c | 560 +++++++++++++++++++++++++++++++++++++
 drivers/virtio/Makefile            |   2 +-
 4 files changed, 610 insertions(+), 4 deletions(-)
 create mode 100644 drivers/virtio/virtio_pci_modern.c
drivers/virtio/virtio_pci_common.h +20 -3
index 38d99ad..1567531 100644
@@ -53,12 +53,29 @@ struct virtio_pci_device {
 	struct virtio_device vdev;
 	struct pci_dev *pci_dev;
 
+	/* In legacy mode, these two point to within ->legacy. */
+	/* Where to read and clear interrupt */
+	u8 __iomem *isr;
+
+	/* Modern only fields */
+	/* The IO mapping for the PCI config space (non-legacy mode) */
+	struct virtio_pci_common_cfg __iomem *common;
+	/* Device-specific data (non-legacy mode)  */
+	void __iomem *device;
+	/* Base of vq notifications (non-legacy mode). */
+	void __iomem *notify_base;
+
+	/* So we can sanity-check accesses. */
+	size_t notify_len;
+	size_t device_len;
+
+	/* Multiply queue_notify_off by this value. (non-legacy mode). */
+	u32 notify_offset_multiplier;
+
+	/* Legacy only field */
 	/* the IO mapping for the PCI config space */
 	void __iomem *ioaddr;
 
-	/* the IO mapping for ISR operation */
-	void __iomem *isr;
-
 	/* a list of queues so we can dispatch IRQs */
 	spinlock_t lock;
 	struct list_head virtqueues;
include/uapi/linux/virtio_pci.h +29 -0
index 8423764..601c66b 100644
@@ -159,6 +159,35 @@ struct virtio_pci_common_cfg {
 	__le32 queue_used_hi;		/* read-write */
 };
 
+/* Macro versions of offsets for the Old Timers! */
+#define VIRTIO_PCI_CAP_VNDR		0
+#define VIRTIO_PCI_CAP_NEXT		1
+#define VIRTIO_PCI_CAP_LEN		2
+#define VIRTIO_PCI_CAP_TYPE_AND_BAR	3
+#define VIRTIO_PCI_CAP_OFFSET		4
+#define VIRTIO_PCI_CAP_LENGTH		8
+
+#define VIRTIO_PCI_NOTIFY_CAP_MULT	12
+
+#define VIRTIO_PCI_COMMON_DFSELECT	0
+#define VIRTIO_PCI_COMMON_DF		4
+#define VIRTIO_PCI_COMMON_GFSELECT	8
+#define VIRTIO_PCI_COMMON_GF		12
+#define VIRTIO_PCI_COMMON_MSIX		16
+#define VIRTIO_PCI_COMMON_NUMQ		18
+#define VIRTIO_PCI_COMMON_STATUS	20
+#define VIRTIO_PCI_COMMON_Q_SELECT	22
+#define VIRTIO_PCI_COMMON_Q_SIZE	24
+#define VIRTIO_PCI_COMMON_Q_MSIX	26
+#define VIRTIO_PCI_COMMON_Q_ENABLE	28
+#define VIRTIO_PCI_COMMON_Q_NOFF	30
+#define VIRTIO_PCI_COMMON_Q_DESCLO	32
+#define VIRTIO_PCI_COMMON_Q_DESCHI	36
+#define VIRTIO_PCI_COMMON_Q_AVAILLO	40
+#define VIRTIO_PCI_COMMON_Q_AVAILHI	44
+#define VIRTIO_PCI_COMMON_Q_USEDLO	48
+#define VIRTIO_PCI_COMMON_Q_USEDHI	52
+
 #endif /* VIRTIO_PCI_NO_MODERN */
 
 #endif
drivers/virtio/virtio_pci_modern.c new file +560 -0

560 lines not on this page · raw message

drivers/virtio/Makefile +1 -1
index bf5104b..bd230d1 100644
@@ -1,5 +1,5 @@
 obj-$(CONFIG_VIRTIO) += virtio.o virtio_ring.o
 obj-$(CONFIG_VIRTIO_MMIO) += virtio_mmio.o
 obj-$(CONFIG_VIRTIO_PCI) += virtio_pci.o
-virtio_pci-y := virtio_pci_legacy.o virtio_pci_common.o
+virtio_pci-y := virtio_pci_modern.o virtio_pci_legacy.o virtio_pci_common.o
 obj-$(CONFIG_VIRTIO_BALLOON) += virtio_balloon.o
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#9 lore raw

RFC PATCH 5/5 virtio_pci: macros for PCI layout offsets.

In reply to Michael S. Tsirkin

From: Rusty Russell <[email protected]>

QEMU wants it, so why not? Trust, but verify.

Signed-off-by Rusty Russell <[email protected]>
---
 drivers/virtio/virtio_pci_modern.c | 61 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
drivers/virtio/virtio_pci_modern.c +61 -0
index e6e65e1..19568da 100644
@@ -406,6 +406,65 @@ static void __iomem *map_capability(struct pci_dev *dev, int off, size_t minlen,
 	return p;
 }
 
+/* This is part of the ABI.  Don't screw with it. */
+static inline void check_offsets(void)
+{
+	/* Note: disk space was harmed in compilation of this function. */
+	BUILD_BUG_ON(VIRTIO_PCI_CAP_VNDR !=
+		     offsetof(struct virtio_pci_cap, cap_vndr));
+	BUILD_BUG_ON(VIRTIO_PCI_CAP_NEXT !=
+		     offsetof(struct virtio_pci_cap, cap_next));
+	BUILD_BUG_ON(VIRTIO_PCI_CAP_LEN !=
+		     offsetof(struct virtio_pci_cap, cap_len));
+	BUILD_BUG_ON(VIRTIO_PCI_CAP_TYPE_AND_BAR !=
+		     offsetof(struct virtio_pci_cap, type_and_bar));
+	BUILD_BUG_ON(VIRTIO_PCI_CAP_OFFSET !=
+		     offsetof(struct virtio_pci_cap, offset));
+	BUILD_BUG_ON(VIRTIO_PCI_CAP_LENGTH !=
+		     offsetof(struct virtio_pci_cap, length));
+	BUILD_BUG_ON(VIRTIO_PCI_NOTIFY_CAP_MULT !=
+		     offsetof(struct virtio_pci_notify_cap,
+			      notify_off_multiplier));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_DFSELECT !=
+		     offsetof(struct virtio_pci_common_cfg,
+			      device_feature_select));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_DF !=
+		     offsetof(struct virtio_pci_common_cfg, device_feature));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_GFSELECT !=
+		     offsetof(struct virtio_pci_common_cfg,
+			      guest_feature_select));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_GF !=
+		     offsetof(struct virtio_pci_common_cfg, guest_feature));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_MSIX !=
+		     offsetof(struct virtio_pci_common_cfg, msix_config));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_NUMQ !=
+		     offsetof(struct virtio_pci_common_cfg, num_queues));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_STATUS !=
+		     offsetof(struct virtio_pci_common_cfg, device_status));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_SELECT !=
+		     offsetof(struct virtio_pci_common_cfg, queue_select));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_SIZE !=
+		     offsetof(struct virtio_pci_common_cfg, queue_size));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_MSIX !=
+		     offsetof(struct virtio_pci_common_cfg, queue_msix_vector));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_ENABLE !=
+		     offsetof(struct virtio_pci_common_cfg, queue_enable));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_NOFF !=
+		     offsetof(struct virtio_pci_common_cfg, queue_notify_off));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_DESCLO !=
+		     offsetof(struct virtio_pci_common_cfg, queue_desc_lo));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_DESCHI !=
+		     offsetof(struct virtio_pci_common_cfg, queue_desc_hi));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_AVAILLO !=
+		     offsetof(struct virtio_pci_common_cfg, queue_avail_lo));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_AVAILHI !=
+		     offsetof(struct virtio_pci_common_cfg, queue_avail_hi));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_USEDLO !=
+		     offsetof(struct virtio_pci_common_cfg, queue_used_lo));
+	BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_USEDHI !=
+		     offsetof(struct virtio_pci_common_cfg, queue_used_hi));
+}
+
 /* the PCI probing function */
 static int virtio_pci_probe(struct pci_dev *pci_dev,
 			    const struct pci_device_id *id)

@@ -413,6 +472,8 @@ static int virtio_pci_probe(struct pci_dev *pci_dev,
 	struct virtio_pci_device *vp_dev;
 	int err, common, isr, notify, device;
 
+	check_offsets();
+
 	/* We only own devices >= 0x1000 and <= 0x107f: leave the rest. */
 	if (pci_dev->device < 0x1000 || pci_dev->device > 0x107f)
 		return -ENODEV;
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