thr3ads.net - Linux Virtualization - [RFC] virtio-mmio: Update the device to OASIS spec version [Dec 2014]

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Pawel Moll

2014-Dec-19 18:38 UTC

[RFC] virtio-mmio: Update the device to OASIS spec version

This patch add a support for second version of the virtio-mmio device,
which follows OASIS "Virtual I/O Device (VIRTIO) Version 1.0"
specification.

Main changes:

1. The control register symbolic names use the new device/driver
   nomenclature rather than the old guest/host one.

2. The driver detect the device version (version 1 is the pre-OASIS
   spec, version 2 is compatible with fist revision of the OASIS spec)
   and drives the device accordingly.

3. New version uses direct addressing (64 bit address split into two
   low/high register) instead of the guest page size based one,
   and addresses each part of the queue (descriptors, available, used)
   separately.

4. The device activity is now explicitly triggered by writing to the
   "queue ready" register.

5. The platform device got a sysfs attribute with the version number.

6. Whole 64 bit features are properly handled now (both ways).

Signed-off-by: Pawel Moll <pawel.moll at arm.com>
---
I had the code typed for months now, but finally (just before
disappearing for the end-of-year break) got time to test it (and
fix the bugs), so I though I'd share it at least as RFC.

It's based on Linus tree still in merge window, but as far as I can
see all virtio changes have been already pulled, so I don't expect
any changes in rc1.

Tested with our custom models (*not* qemu).

Regards and till next year!

Pawel

 drivers/virtio/virtio_mmio.c | 132 +++++++++++++++++++++++++++----------------
 include/linux/virtio_mmio.h  |  46 +++++++++++----
 2 files changed, 120 insertions(+), 58 deletions(-)

diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index 00d115b..d60675a 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -1,7 +1,7 @@
 /*
  * Virtio memory mapped device driver
  *
- * Copyright 2011, ARM Ltd.
+ * Copyright 2011-2014, ARM Ltd.
  *
  * This module allows virtio devices to be used over a virtual, memory mapped
  * platform device.
@@ -50,36 +50,6 @@
  *
  *
  *
- * Registers layout (all 32-bit wide):
- *
- * offset d. name             description
- * ------ -- ---------------- -----------------
- *
- * 0x000  R  MagicValue       Magic value "virt"
- * 0x004  R  Version          Device version (current max. 1)
- * 0x008  R  DeviceID         Virtio device ID
- * 0x00c  R  VendorID         Virtio vendor ID
- *
- * 0x010  R  HostFeatures     Features supported by the host
- * 0x014  W  HostFeaturesSel  Set of host features to access via HostFeatures
- *
- * 0x020  W  GuestFeatures    Features activated by the guest
- * 0x024  W  GuestFeaturesSel Set of activated features to set via
GuestFeatures
- * 0x028  W  GuestPageSize    Size of guest's memory page in bytes
- *
- * 0x030  W  QueueSel         Queue selector
- * 0x034  R  QueueNumMax      Maximum size of the currently selected queue
- * 0x038  W  QueueNum         Queue size for the currently selected queue
- * 0x03c  W  QueueAlign       Used Ring alignment for the current queue
- * 0x040  RW QueuePFN         PFN for the currently selected queue
- *
- * 0x050  W  QueueNotify      Queue notifier
- * 0x060  R  InterruptStatus  Interrupt status register
- * 0x064  W  InterruptACK     Interrupt acknowledge register
- * 0x070  RW Status           Device status register
- *
- * 0x100+ RW                  Device-specific configuration space
- *
  * Based on Virtio PCI driver by Anthony Liguori, copyright IBM Corp. 2007
  *
  * This work is licensed under the terms of the GNU GPL, version 2 or later.
@@ -145,11 +115,16 @@ struct virtio_mmio_vq_info {
 static u64 vm_get_features(struct virtio_device *vdev)
 {
 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
+	u64 features;
+
+	writel(1, vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES_SEL);
+	features = readl(vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES);
+	features <<= 32;
 
-	/* TODO: Features > 32 bits */
-	writel(0, vm_dev->base + VIRTIO_MMIO_HOST_FEATURES_SEL);
+	writel(0, vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES_SEL);
+	features |= readl(vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES);
 
-	return readl(vm_dev->base + VIRTIO_MMIO_HOST_FEATURES);
+	return features;
 }
 
 static int vm_finalize_features(struct virtio_device *vdev)
@@ -159,11 +134,13 @@ static int vm_finalize_features(struct virtio_device
*vdev)
 	/* Give virtio_ring a chance to accept features. */
 	vring_transport_features(vdev);
 
-	/* Make sure we don't have any features > 32 bits! */
-	BUG_ON((u32)vdev->features != vdev->features);
+	writel(1, vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES_SEL);
+	writel((vdev->features >> 32) & 0xffffffff,
+			vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES);
 
-	writel(0, vm_dev->base + VIRTIO_MMIO_GUEST_FEATURES_SEL);
-	writel(vdev->features, vm_dev->base + VIRTIO_MMIO_GUEST_FEATURES);
+	writel(0, vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES_SEL);
+	writel(vdev->features & 0xffffffff,
+			vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES);
 
 	return 0;
 }
@@ -275,7 +252,12 @@ static void vm_del_vq(struct virtqueue *vq)
 
 	/* Select and deactivate the queue */
 	writel(index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);
-	writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
+	if (vm_dev->version == 1) {
+		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
+	} else {
+		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
+		WARN_ON(readl(vm_dev->base + VIRTIO_MMIO_QUEUE_READY));
+	}
 
 	size = PAGE_ALIGN(vring_size(info->num, VIRTIO_MMIO_VRING_ALIGN));
 	free_pages_exact(info->queue, size);
@@ -312,7 +294,8 @@ static struct virtqueue *vm_setup_vq(struct virtio_device
*vdev, unsigned index,
 	writel(index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);
 
 	/* Queue shouldn't already be set up. */
-	if (readl(vm_dev->base + VIRTIO_MMIO_QUEUE_PFN)) {
+	if (readl(vm_dev->base + (vm_dev->version == 1 ?
+			VIRTIO_MMIO_QUEUE_PFN : VIRTIO_MMIO_QUEUE_READY))) {
 		err = -ENOENT;
 		goto error_available;
 	}
@@ -358,10 +341,35 @@ static struct virtqueue *vm_setup_vq(struct virtio_device
*vdev, unsigned index,
 
 	/* Activate the queue */
 	writel(info->num, vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
-	writel(VIRTIO_MMIO_VRING_ALIGN,
-			vm_dev->base + VIRTIO_MMIO_QUEUE_ALIGN);
-	writel(virt_to_phys(info->queue) >> PAGE_SHIFT,
-			vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
+	if (vm_dev->version == 1) {
+		writel(VIRTIO_MMIO_VRING_ALIGN,
+				vm_dev->base + VIRTIO_MMIO_QUEUE_ALIGN);
+		writel(virt_to_phys(info->queue) >> PAGE_SHIFT,
+				vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
+	} else {
+		uint64_t addr = virt_to_phys(info->queue);
+
+		writel(addr & 0xffffffff,
+				vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_LOW);
+		writel((addr >> 32) & 0xffffffff,
+				vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_HIGH);
+
+		addr += info->num * sizeof(struct vring_desc);
+		writel(addr & 0xffffffff,
+				vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_LOW);
+		writel((addr >> 32) & 0xffffffff,
+				vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_HIGH);
+
+		addr += sizeof(struct vring_avail) + info->num * sizeof(__u16);
+		addr += VIRTIO_MMIO_VRING_ALIGN - 1;
+		addr &= ~(VIRTIO_MMIO_VRING_ALIGN - 1);
+		writel(addr & 0xffffffff,
+				vm_dev->base + VIRTIO_MMIO_QUEUE_USED_LOW);
+		writel((addr >> 32) & 0xffffffff,
+				vm_dev->base + VIRTIO_MMIO_QUEUE_USED_HIGH);
+
+		writel(1, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
+	}
 
 	/* Create the vring */
 	vq = vring_new_virtqueue(index, info->num, VIRTIO_MMIO_VRING_ALIGN, vdev,
@@ -381,7 +389,12 @@ static struct virtqueue *vm_setup_vq(struct virtio_device
*vdev, unsigned index,
 	return vq;
 
 error_new_virtqueue:
-	writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
+	if (vm_dev->version == 1) {
+		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
+	} else {
+		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
+		WARN_ON(readl(vm_dev->base + VIRTIO_MMIO_QUEUE_READY));
+	}
 	free_pages_exact(info->queue, size);
 error_alloc_pages:
 	kfree(info);
@@ -439,6 +452,18 @@ static const struct virtio_config_ops
virtio_mmio_config_ops = {
 
 /* Platform device */
 
+static ssize_t vm_dev_attr_version_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct virtio_mmio_device *vm_dev = platform_get_drvdata(pdev);
+
+	return snprintf(buf, PAGE_SIZE, "%lu", vm_dev->version);
+}
+
+static struct device_attribute vm_dev_attr_version +		__ATTR(version, S_IRUGO,
vm_dev_attr_version_show, NULL);
+
 static int virtio_mmio_probe(struct platform_device *pdev)
 {
 	struct virtio_mmio_device *vm_dev;
@@ -476,16 +501,26 @@ static int virtio_mmio_probe(struct platform_device *pdev)
 
 	/* Check device version */
 	vm_dev->version = readl(vm_dev->base + VIRTIO_MMIO_VERSION);
-	if (vm_dev->version != 1) {
+	if (vm_dev->version < 1 || vm_dev->version > 2) {
 		dev_err(&pdev->dev, "Version %ld not supported!\n",
 				vm_dev->version);
 		return -ENXIO;
 	}
 
 	vm_dev->vdev.id.device = readl(vm_dev->base + VIRTIO_MMIO_DEVICE_ID);
+	if (vm_dev->vdev.id.device == 0) {
+		/*
+		 * ID 0 means a dummy (placeholder) device, skip quietly
+		 * (as in: no error) with no further actions
+		 */
+		return 0;
+	}
 	vm_dev->vdev.id.vendor = readl(vm_dev->base + VIRTIO_MMIO_VENDOR_ID);
 
-	writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE);
+	if (vm_dev->version == 1)
+		writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE);
+
+	device_create_file(&pdev->dev, &vm_dev_attr_version);
 
 	platform_set_drvdata(pdev, vm_dev);
 
@@ -496,7 +531,8 @@ static int virtio_mmio_remove(struct platform_device *pdev)
 {
 	struct virtio_mmio_device *vm_dev = platform_get_drvdata(pdev);
 
-	unregister_virtio_device(&vm_dev->vdev);
+	if (vm_dev)
+		unregister_virtio_device(&vm_dev->vdev);
 
 	return 0;
 }
diff --git a/include/linux/virtio_mmio.h b/include/linux/virtio_mmio.h
index 5c7b6f0..d5f3634 100644
--- a/include/linux/virtio_mmio.h
+++ b/include/linux/virtio_mmio.h
@@ -51,21 +51,22 @@
 /* Virtio vendor ID - Read Only */
 #define VIRTIO_MMIO_VENDOR_ID		0x00c
 
-/* Bitmask of the features supported by the host
+/* Bitmask of the features supported by the device (host)
  * (32 bits per set) - Read Only */
-#define VIRTIO_MMIO_HOST_FEATURES	0x010
+#define VIRTIO_MMIO_DEVICE_FEATURES	0x010
 
-/* Host features set selector - Write Only */
-#define VIRTIO_MMIO_HOST_FEATURES_SEL	0x014
+/* Device (host) features set selector - Write Only */
+#define VIRTIO_MMIO_DEVICE_FEATURES_SEL	0x014
 
-/* Bitmask of features activated by the guest
+/* Bitmask of features activated by the driver (guest)
  * (32 bits per set) - Write Only */
-#define VIRTIO_MMIO_GUEST_FEATURES	0x020
+#define VIRTIO_MMIO_DRIVER_FEATURES	0x020
 
 /* Activated features set selector - Write Only */
-#define VIRTIO_MMIO_GUEST_FEATURES_SEL	0x024
+#define VIRTIO_MMIO_DRIVER_FEATURES_SEL	0x024
 
-/* Guest's memory page size in bytes - Write Only */
+/* Guest's memory page size in bytes - Write Only
+ * LEGACY DEVICES ONLY! */
 #define VIRTIO_MMIO_GUEST_PAGE_SIZE	0x028
 
 /* Queue selector - Write Only */
@@ -77,12 +78,18 @@
 /* Queue size for the currently selected queue - Write Only */
 #define VIRTIO_MMIO_QUEUE_NUM		0x038
 
-/* Used Ring alignment for the currently selected queue - Write Only */
+/* Used Ring alignment for the currently selected queue - Write Only
+ * LEGACY DEVICES ONLY! */
 #define VIRTIO_MMIO_QUEUE_ALIGN		0x03c
 
-/* Guest's PFN for the currently selected queue - Read Write */
+/* Guest's PFN for the currently selected queue - Read Write
+ * LEGACY DEVICES ONLY! */
 #define VIRTIO_MMIO_QUEUE_PFN		0x040
 
+/* Ready bit for the currently selected queue - Read Write
+ * NOT FOR LEGACY DEVICES! */
+#define VIRTIO_MMIO_QUEUE_READY		0x044
+
 /* Queue notifier - Write Only */
 #define VIRTIO_MMIO_QUEUE_NOTIFY	0x050
 
@@ -95,6 +102,25 @@
 /* Device status register - Read Write */
 #define VIRTIO_MMIO_STATUS		0x070
 
+/* Selected queue's Descriptor Table address, 64 bits in two halves
+ * NOT FOR LEGACY DEVICES! */
+#define VIRTIO_MMIO_QUEUE_DESC_LOW	0x080
+#define VIRTIO_MMIO_QUEUE_DESC_HIGH	0x084
+
+/* Selected queue's Available Ring address, 64 bits in two halves
+ * NOT FOR LEGACY DEVICES! */
+#define VIRTIO_MMIO_QUEUE_AVAIL_LOW	0x090
+#define VIRTIO_MMIO_QUEUE_AVAIL_HIGH	0x094
+
+/* Selected queue's Used Ring address, 64 bits in two halves
+ * NOT FOR LEGACY DEVICES! */
+#define VIRTIO_MMIO_QUEUE_USED_LOW	0x0a0
+#define VIRTIO_MMIO_QUEUE_USED_HIGH	0x0a4
+
+/* Configuration atomicity value
+ * NOT FOR LEGACY DEVICES! */
+#define VIRTIO_MMIO_CONFIG_GENERATION	0x0fc
+
 /* The config space is defined by each driver as
  * the per-driver configuration space - Read Write */
 #define VIRTIO_MMIO_CONFIG		0x100
-- 
2.1.0

Michael S. Tsirkin

2015-Jan-15 16:51 UTC

head link

[RFC] virtio-mmio: Update the device to OASIS spec version

On Fri, Dec 19, 2014 at 06:38:04PM +0000, Pawel Moll
wrote:> This patch add a support for second version of the virtio-mmio device,
> which follows OASIS "Virtual I/O Device (VIRTIO) Version 1.0"
> specification.
> 
> Main changes:
> 
> 1. The control register symbolic names use the new device/driver
>    nomenclature rather than the old guest/host one.
> 
> 2. The driver detect the device version (version 1 is the pre-OASIS
>    spec, version 2 is compatible with fist revision of the OASIS spec)
>    and drives the device accordingly.
> 
> 3. New version uses direct addressing (64 bit address split into two
>    low/high register) instead of the guest page size based one,
>    and addresses each part of the queue (descriptors, available, used)
>    separately.
> 
> 4. The device activity is now explicitly triggered by writing to the
>    "queue ready" register.
> 
> 5. The platform device got a sysfs attribute with the version number.
> 
> 6. Whole 64 bit features are properly handled now (both ways).
> 
> Signed-off-by: Pawel Moll <pawel.moll at arm.com>
> ---
> I had the code typed for months now, but finally (just before
> disappearing for the end-of-year break) got time to test it (and
> fix the bugs), so I though I'd share it at least as RFC.
> 
> It's based on Linus tree still in merge window, but as far as I can
> see all virtio changes have been already pulled, so I don't expect
> any changes in rc1.
> 
> Tested with our custom models (*not* qemu).
> 
> Regards and till next year!
> 
> Pawel
> 
>  drivers/virtio/virtio_mmio.c | 132
+++++++++++++++++++++++++++----------------
>  include/linux/virtio_mmio.h  |  46 +++++++++++----
>  2 files changed, 120 insertions(+), 58 deletions(-)
Thanks!  Looks good overall. Some comments below.

> diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> index 00d115b..d60675a 100644
> --- a/drivers/virtio/virtio_mmio.c
> +++ b/drivers/virtio/virtio_mmio.c
> @@ -1,7 +1,7 @@
>  /*
>   * Virtio memory mapped device driver
>   *
> - * Copyright 2011, ARM Ltd.
> + * Copyright 2011-2014, ARM Ltd.
>   *
>   * This module allows virtio devices to be used over a virtual, memory
mapped
>   * platform device.
> @@ -50,36 +50,6 @@
>   *
>   *
>   *
> - * Registers layout (all 32-bit wide):
> - *
> - * offset d. name             description
> - * ------ -- ---------------- -----------------
> - *
> - * 0x000  R  MagicValue       Magic value "virt"
> - * 0x004  R  Version          Device version (current max. 1)
> - * 0x008  R  DeviceID         Virtio device ID
> - * 0x00c  R  VendorID         Virtio vendor ID
> - *
> - * 0x010  R  HostFeatures     Features supported by the host
> - * 0x014  W  HostFeaturesSel  Set of host features to access via
HostFeatures
> - *
> - * 0x020  W  GuestFeatures    Features activated by the guest
> - * 0x024  W  GuestFeaturesSel Set of activated features to set via
GuestFeatures
> - * 0x028  W  GuestPageSize    Size of guest's memory page in bytes
> - *
> - * 0x030  W  QueueSel         Queue selector
> - * 0x034  R  QueueNumMax      Maximum size of the currently selected queue
> - * 0x038  W  QueueNum         Queue size for the currently selected queue
> - * 0x03c  W  QueueAlign       Used Ring alignment for the current queue
> - * 0x040  RW QueuePFN         PFN for the currently selected queue
> - *
> - * 0x050  W  QueueNotify      Queue notifier
> - * 0x060  R  InterruptStatus  Interrupt status register
> - * 0x064  W  InterruptACK     Interrupt acknowledge register
> - * 0x070  RW Status           Device status register
> - *
> - * 0x100+ RW                  Device-specific configuration space
> - *
>   * Based on Virtio PCI driver by Anthony Liguori, copyright IBM Corp. 2007
>   *
>   * This work is licensed under the terms of the GNU GPL, version 2 or
later.
> @@ -145,11 +115,16 @@ struct virtio_mmio_vq_info {
>  static u64 vm_get_features(struct virtio_device *vdev)
>  {
>  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
> +	u64 features;
> +
> +	writel(1, vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES_SEL);
> +	features = readl(vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES);
> +	features <<= 32;
>  
> -	/* TODO: Features > 32 bits */
> -	writel(0, vm_dev->base + VIRTIO_MMIO_HOST_FEATURES_SEL);
> +	writel(0, vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES_SEL);
> +	features |= readl(vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES);
>  
> -	return readl(vm_dev->base + VIRTIO_MMIO_HOST_FEATURES);
> +	return features;
>  }
>  
>  static int vm_finalize_features(struct virtio_device *vdev)
> @@ -159,11 +134,13 @@ static int vm_finalize_features(struct virtio_device
*vdev)
>  	/* Give virtio_ring a chance to accept features. */
>  	vring_transport_features(vdev);
>  
> -	/* Make sure we don't have any features > 32 bits! */
> -	BUG_ON((u32)vdev->features != vdev->features);
> +	writel(1, vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES_SEL);
> +	writel((vdev->features >> 32) & 0xffffffff,
> +			vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES);
>  
> -	writel(0, vm_dev->base + VIRTIO_MMIO_GUEST_FEATURES_SEL);
> -	writel(vdev->features, vm_dev->base + VIRTIO_MMIO_GUEST_FEATURES);
> +	writel(0, vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES_SEL);
> +	writel(vdev->features & 0xffffffff,
> +			vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES);
>  
>  	return 0;
>  }
> @@ -275,7 +252,12 @@ static void vm_del_vq(struct virtqueue *vq)
>  
>  	/* Select and deactivate the queue */
>  	writel(index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);
> -	writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
> +	if (vm_dev->version == 1) {
> +		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
> +	} else {
> +		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
> +		WARN_ON(readl(vm_dev->base + VIRTIO_MMIO_QUEUE_READY));
> +	}
>  
>  	size = PAGE_ALIGN(vring_size(info->num, VIRTIO_MMIO_VRING_ALIGN));
>  	free_pages_exact(info->queue, size);
> @@ -312,7 +294,8 @@ static struct virtqueue *vm_setup_vq(struct
virtio_device *vdev, unsigned index,
>  	writel(index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);
>  
>  	/* Queue shouldn't already be set up. */
> -	if (readl(vm_dev->base + VIRTIO_MMIO_QUEUE_PFN)) {
> +	if (readl(vm_dev->base + (vm_dev->version == 1 ?
> +			VIRTIO_MMIO_QUEUE_PFN : VIRTIO_MMIO_QUEUE_READY))) {
>  		err = -ENOENT;
>  		goto error_available;
>  	}
> @@ -358,10 +341,35 @@ static struct virtqueue *vm_setup_vq(struct
virtio_device *vdev, unsigned index,
>  
>  	/* Activate the queue */
>  	writel(info->num, vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
> -	writel(VIRTIO_MMIO_VRING_ALIGN,
> -			vm_dev->base + VIRTIO_MMIO_QUEUE_ALIGN);
> -	writel(virt_to_phys(info->queue) >> PAGE_SHIFT,
> -			vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
> +	if (vm_dev->version == 1) {
> +		writel(VIRTIO_MMIO_VRING_ALIGN,
> +				vm_dev->base + VIRTIO_MMIO_QUEUE_ALIGN);
> +		writel(virt_to_phys(info->queue) >> PAGE_SHIFT,
> +				vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
> +	} else {
> +		uint64_t addr = virt_to_phys(info->queue);
Kernel normally uses u64 for this type.
> +
> +		writel(addr & 0xffffffff,
> +				vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_LOW);
> +		writel((addr >> 32) & 0xffffffff,
> +				vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_HIGH);
> +
> +		addr += info->num * sizeof(struct vring_desc);
> +		writel(addr & 0xffffffff,
> +				vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_LOW);
> +		writel((addr >> 32) & 0xffffffff,
> +				vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_HIGH);
0xffffffff isn't really needed, is it?
> +
> +		addr += sizeof(struct vring_avail) + info->num * sizeof(__u16);
> +		addr += VIRTIO_MMIO_VRING_ALIGN - 1;
> +		addr &= ~(VIRTIO_MMIO_VRING_ALIGN - 1);

Host no longer knows the alignment, so why is it needed?
In fact, I notice that 4.3.2.3 Virtqueue Layout seems completely wrong:
it corresponds to legacy devices, and it does not
say what "align" is.

I think you shouldn't use VIRTIO_MMIO_VRING_ALIGN in non-legacy code:
it's a legacy thing.



> +		writel(addr & 0xffffffff,
> +				vm_dev->base + VIRTIO_MMIO_QUEUE_USED_LOW);
> +		writel((addr >> 32) & 0xffffffff,
> +				vm_dev->base + VIRTIO_MMIO_QUEUE_USED_HIGH);
> +
> +		writel(1, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
> +	}
>  
>  	/* Create the vring */
>  	vq = vring_new_virtqueue(index, info->num, VIRTIO_MMIO_VRING_ALIGN,
vdev,
> @@ -381,7 +389,12 @@ static struct virtqueue *vm_setup_vq(struct
virtio_device *vdev, unsigned index,
>  	return vq;
>  
>  error_new_virtqueue:
> -	writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
> +	if (vm_dev->version == 1) {
> +		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
> +	} else {
> +		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
> +		WARN_ON(readl(vm_dev->base + VIRTIO_MMIO_QUEUE_READY));
> +	}
>  	free_pages_exact(info->queue, size);
>  error_alloc_pages:
>  	kfree(info);
> @@ -439,6 +452,18 @@ static const struct virtio_config_ops
virtio_mmio_config_ops = {
>  
>  /* Platform device */
>  
> +static ssize_t vm_dev_attr_version_show(struct device *dev,
> +		struct device_attribute *attr, char *buf)
> +{
> +	struct platform_device *pdev = to_platform_device(dev);
> +	struct virtio_mmio_device *vm_dev = platform_get_drvdata(pdev);
> +
> +	return snprintf(buf, PAGE_SIZE, "%lu", vm_dev->version);
> +}
> +
> +static struct device_attribute vm_dev_attr_version > +		__ATTR(version,
S_IRUGO, vm_dev_attr_version_show, NULL);
> +
>  static int virtio_mmio_probe(struct platform_device *pdev)
>  {
>  	struct virtio_mmio_device *vm_dev;
We already expose feature bits - this one really necessary?
> @@ -476,16 +501,26 @@ static int virtio_mmio_probe(struct platform_device
*pdev)
>  
>  	/* Check device version */
>  	vm_dev->version = readl(vm_dev->base + VIRTIO_MMIO_VERSION);
> -	if (vm_dev->version != 1) {
> +	if (vm_dev->version < 1 || vm_dev->version > 2) {
>  		dev_err(&pdev->dev, "Version %ld not supported!\n",
>  				vm_dev->version);
>  		return -ENXIO;
>  	}
>  
>  	vm_dev->vdev.id.device = readl(vm_dev->base +
VIRTIO_MMIO_DEVICE_ID);
> +	if (vm_dev->vdev.id.device == 0) {
> +		/*
> +		 * ID 0 means a dummy (placeholder) device, skip quietly
> +		 * (as in: no error) with no further actions
> +		 */
> +		return 0;
Necessary?
We don't have drivers for this id anyway.
> +	}
Need to also
	1. validate that feature bit VIRTIO_1 is set
	2. validate that ID is not for a legacy device

otherwise device specific drivers might get invoked
on future devices (e.g. when we update balloon for 1.0)
and they not do the right thing.

>  	vm_dev->vdev.id.vendor = readl(vm_dev->base +
VIRTIO_MMIO_VENDOR_ID);
>  
> -	writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE);
> +	if (vm_dev->version == 1)
> +		writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE);
> +
> +	device_create_file(&pdev->dev, &vm_dev_attr_version);
>  
>  	platform_set_drvdata(pdev, vm_dev);
>  
> @@ -496,7 +531,8 @@ static int virtio_mmio_remove(struct platform_device
*pdev)
>  {
>  	struct virtio_mmio_device *vm_dev = platform_get_drvdata(pdev);
>  
> -	unregister_virtio_device(&vm_dev->vdev);
> +	if (vm_dev)
> +		unregister_virtio_device(&vm_dev->vdev);
>  
Will remove ever be called if probe fails?
>  	return 0;
>  }
> diff --git a/include/linux/virtio_mmio.h b/include/linux/virtio_mmio.h
> index 5c7b6f0..d5f3634 100644
> --- a/include/linux/virtio_mmio.h
> +++ b/include/linux/virtio_mmio.h
> @@ -51,21 +51,22 @@
>  /* Virtio vendor ID - Read Only */
>  #define VIRTIO_MMIO_VENDOR_ID		0x00c
>  
> -/* Bitmask of the features supported by the host
> +/* Bitmask of the features supported by the device (host)
>   * (32 bits per set) - Read Only */
> -#define VIRTIO_MMIO_HOST_FEATURES	0x010
> +#define VIRTIO_MMIO_DEVICE_FEATURES	0x010
>  
> -/* Host features set selector - Write Only */
> -#define VIRTIO_MMIO_HOST_FEATURES_SEL	0x014
> +/* Device (host) features set selector - Write Only */
> +#define VIRTIO_MMIO_DEVICE_FEATURES_SEL	0x014
>  
> -/* Bitmask of features activated by the guest
> +/* Bitmask of features activated by the driver (guest)
>   * (32 bits per set) - Write Only */
> -#define VIRTIO_MMIO_GUEST_FEATURES	0x020
> +#define VIRTIO_MMIO_DRIVER_FEATURES	0x020
>  
>  /* Activated features set selector - Write Only */
> -#define VIRTIO_MMIO_GUEST_FEATURES_SEL	0x024
> +#define VIRTIO_MMIO_DRIVER_FEATURES_SEL	0x024
>  
> -/* Guest's memory page size in bytes - Write Only */
> +/* Guest's memory page size in bytes - Write Only
> + * LEGACY DEVICES ONLY! */
This is not the preferred style for multi-line comments :)
Also - maybe add a flag to selectively disable legacy
or modern macros?
Might be clearer than comments that, after all, never compile.
>  #define VIRTIO_MMIO_GUEST_PAGE_SIZE	0x028
>  
>  /* Queue selector - Write Only */
> @@ -77,12 +78,18 @@
>  /* Queue size for the currently selected queue - Write Only */
>  #define VIRTIO_MMIO_QUEUE_NUM		0x038
>  
> -/* Used Ring alignment for the currently selected queue - Write Only */
> +/* Used Ring alignment for the currently selected queue - Write Only
> + * LEGACY DEVICES ONLY! */
>  #define VIRTIO_MMIO_QUEUE_ALIGN		0x03c
>  
> -/* Guest's PFN for the currently selected queue - Read Write */
> +/* Guest's PFN for the currently selected queue - Read Write
> + * LEGACY DEVICES ONLY! */
>  #define VIRTIO_MMIO_QUEUE_PFN		0x040
>  
> +/* Ready bit for the currently selected queue - Read Write
> + * NOT FOR LEGACY DEVICES! */
> +#define VIRTIO_MMIO_QUEUE_READY		0x044
> +
>  /* Queue notifier - Write Only */
>  #define VIRTIO_MMIO_QUEUE_NOTIFY	0x050
>  
> @@ -95,6 +102,25 @@
>  /* Device status register - Read Write */
>  #define VIRTIO_MMIO_STATUS		0x070
>  
> +/* Selected queue's Descriptor Table address, 64 bits in two halves
> + * NOT FOR LEGACY DEVICES! */
> +#define VIRTIO_MMIO_QUEUE_DESC_LOW	0x080
> +#define VIRTIO_MMIO_QUEUE_DESC_HIGH	0x084
> +
> +/* Selected queue's Available Ring address, 64 bits in two halves
> + * NOT FOR LEGACY DEVICES! */
> +#define VIRTIO_MMIO_QUEUE_AVAIL_LOW	0x090
> +#define VIRTIO_MMIO_QUEUE_AVAIL_HIGH	0x094
> +
> +/* Selected queue's Used Ring address, 64 bits in two halves
> + * NOT FOR LEGACY DEVICES! */
> +#define VIRTIO_MMIO_QUEUE_USED_LOW	0x0a0
> +#define VIRTIO_MMIO_QUEUE_USED_HIGH	0x0a4
> +
> +/* Configuration atomicity value
> + * NOT FOR LEGACY DEVICES! */
> +#define VIRTIO_MMIO_CONFIG_GENERATION	0x0fc
> +
>  /* The config space is defined by each driver as
>   * the per-driver configuration space - Read Write */
>  #define VIRTIO_MMIO_CONFIG		0x100
> -- 
> 2.1.0
> 
> _______________________________________________
> Virtualization mailing list
> Virtualization at lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/virtualization

Michael S. Tsirkin

2015-Jan-15 17:12 UTC

head link

[RFC] virtio-mmio: Update the device to OASIS spec version

On Thu, Jan 15, 2015 at 06:51:01PM +0200, Michael S. Tsirkin
wrote:> Host no longer knows the alignment, so why is it needed?
> In fact, I notice that 4.3.2.3 Virtqueue Layout seems completely wrong:
> it corresponds to legacy devices, and it does not
> say what "align" is.
I created
https://issues.oasis-open.org/browse/VIRTIO-129
to track this. Can you write up a patch please?

-- 
MST

Pawel Moll

2015-Jan-15 17:32 UTC

head link

[RFC] virtio-mmio: Update the device to OASIS spec version

On Thu, 2015-01-15 at 16:51 +0000, Michael S. Tsirkin
wrote:> > +             uint64_t addr = virt_to_phys(info->queue);
> 
> Kernel normally uses u64 for this type.
Sure, well spotted.
> > +
> > +             writel(addr & 0xffffffff,
> > +                             vm_dev->base +
VIRTIO_MMIO_QUEUE_DESC_LOW);
> > +             writel((addr >> 32) & 0xffffffff,
> > +                             vm_dev->base +
VIRTIO_MMIO_QUEUE_DESC_HIGH);
> > +
> > +             addr += info->num * sizeof(struct vring_desc);
> > +             writel(addr & 0xffffffff,
> > +                             vm_dev->base +
VIRTIO_MMIO_QUEUE_AVAIL_LOW);
> > +             writel((addr >> 32) & 0xffffffff,
> > +                             vm_dev->base +
VIRTIO_MMIO_QUEUE_AVAIL_HIGH);
> 
> 0xffffffff isn't really needed, is it?
I admit I'm never sure what are the narrowing side effects. You are
probably right that u64 >> 32 will be always 32 bit.
> > +
> > +             addr += sizeof(struct vring_avail) + info->num *
sizeof(__u16);
> > +             addr += VIRTIO_MMIO_VRING_ALIGN - 1;
> > +             addr &= ~(VIRTIO_MMIO_VRING_ALIGN - 1);
> 
> 
> Host no longer knows the alignment, so why is it needed?
[skipped the spec reference, it's a separate discussion]
> I think you shouldn't use VIRTIO_MMIO_VRING_ALIGN in non-legacy code:
> it's a legacy thing.
But I still need to pass something to vring_new_virtqueue() below, don't
I? And it will allocate the queue based on some alignment value. I can't
see anything that would create the layout for me, neither in mainline
nor in next. Have I missed something? (wouldn't be surprised if I have)
> > +             writel(addr & 0xffffffff,
> > +                             vm_dev->base +
VIRTIO_MMIO_QUEUE_USED_LOW);
> > +             writel((addr >> 32) & 0xffffffff,
> > +                             vm_dev->base +
VIRTIO_MMIO_QUEUE_USED_HIGH);
> > +
> > +             writel(1, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
> > +     }
> >
> >       /* Create the vring */
> >       vq = vring_new_virtqueue(index, info->num,
VIRTIO_MMIO_VRING_ALIGN, vdev,
[...]
> > +static struct device_attribute vm_dev_attr_version > > +       
__ATTR(version, S_IRUGO, vm_dev_attr_version_show, NULL);
> > +
> >  static int virtio_mmio_probe(struct platform_device *pdev)
> >  {
> >       struct virtio_mmio_device *vm_dev;
> 
> We already expose feature bits - this one really necessary?
Necessary? Of course not, just a debugging feature, really, to see what
version of control registers are available. Useful - I strongly believe
so.
> > @@ -476,16 +501,26 @@ static int virtio_mmio_probe(struct
platform_device *pdev)
> >
> >       /* Check device version */
> >       vm_dev->version = readl(vm_dev->base +
VIRTIO_MMIO_VERSION);
> > -     if (vm_dev->version != 1) {
> > +     if (vm_dev->version < 1 || vm_dev->version > 2) {
> >               dev_err(&pdev->dev, "Version %ld not
supported!\n",
> >                               vm_dev->version);
> >               return -ENXIO;
> >       }
> >
> >       vm_dev->vdev.id.device = readl(vm_dev->base +
VIRTIO_MMIO_DEVICE_ID);
> > +     if (vm_dev->vdev.id.device == 0) {
> > +             /*
> > +              * ID 0 means a dummy (placeholder) device, skip quietly
> > +              * (as in: no error) with no further actions
> > +              */
> > +             return 0;
> 
> Necessary?
> We don't have drivers for this id anyway.
I'm not sure if you are joking or not, after the battle we fought over
it.

The short answer is: yes. Necessary.

"4.2.2 MMIO Device Register Layout

[...]

Virtio Subsystem Device ID
See 5 Device Types for possible values. Value zero (0x0) is used to de-
fine a system memory map with placeholder devices at static, well known
addresses, assigning functions to them depending on user?s needs.

[...]

4.2.2.2 Driver Requirements: MMIO Device Register Layout

The driver MUST ignore a device with DeviceID 0x0, but MUST NOT report
any error."
> > +     }
> 
> Need to also
>         1. validate that feature bit VIRTIO_1 is set
>         2. validate that ID is not for a legacy device
> 
> otherwise device specific drivers might get invoked
> on future devices (e.g. when we update balloon for 1.0)
> and they not do the right thing.
I'm not following you, but I admit I haven't though this problem
thoroughly. If you can volunteer an example of things going on, it would
be useful. Either way, I'll think about it again.
> @@ -496,7 +531,8 @@ static int virtio_mmio_remove(struct platform_device
*pdev)
> >  {
> >       struct virtio_mmio_device *vm_dev = platform_get_drvdata(pdev);
> >
> > -     unregister_virtio_device(&vm_dev->vdev);
> > +     if (vm_dev)
> > +             unregister_virtio_device(&vm_dev->vdev);
> >
> 
> Will remove ever be called if probe fails?
No.
> > -/* Guest's memory page size in bytes - Write Only */
> > +/* Guest's memory page size in bytes - Write Only
> > + * LEGACY DEVICES ONLY! */
> 
> This is not the preferred style for multi-line comments :)
Fact. Will fix.
> Also - maybe add a flag to selectively disable legacy
> or modern macros?
> Might be clearer than comments that, after all, never compile.
As in, a bunch of #ifdefs disabling the legacy lines of code? Doable,
although I'm not sure how beautiful would that be. Will have a look, but
it probably would only make sense with CONFIG_VIRTIO_MMIO_LEGACY option.

Pawe?

Michael S. Tsirkin

2015-Jan-15 18:39 UTC

head link

[RFC] virtio-mmio: Update the device to OASIS spec version

On Fri, Dec 19, 2014 at 06:38:04PM +0000, Pawel Moll
wrote:> Tested with our custom models (*not* qemu).
Could you look into updating qemu as well please?
I'd like to make sure patches are widely testable
before pushing them, to reduce the chances of
finding issues after kernel is released.

You can find draft patches for pci and s390 here:
git://git.kernel.org/pub/scm/virt/kvm/mst/qemu.git virtio-1.0

-- 
MST

Pawel Moll

2015-Jan-15 18:51 UTC

head link

[RFC] virtio-mmio: Update the device to OASIS spec version

On Thu, 2015-01-15 at 18:39 +0000, Michael S. Tsirkin
wrote:> On Fri, Dec 19, 2014 at 06:38:04PM +0000, Pawel Moll wrote:
> > Tested with our custom models (*not* qemu).
> 
> Could you look into updating qemu as well please?
No, sorry. I'm officially not allowed to touch qemu, due to some legal
issues.

I'll talk to Peter Maydell.

Pawe?

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