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Date: Wed, 23 Nov 2011 11:44:53 +0200
From: Sasha Levin <levinsasha928@...il.com>
To: Rusty Russell <rusty@...tcorp.com.au>
Cc: "Michael S. Tsirkin" <mst@...hat.com>,
lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>,
Alexey Kardashevskiy <aik@...abs.ru>,
Amit Shah <amit.shah@...hat.com>,
Christian Borntraeger <borntraeger@...ibm.com>,
Krishna Kumar <krkumar2@...ibm.com>,
Pawel Moll <pawel.moll@....com>,
Wang Sheng-Hui <shhuiw@...il.com>,
virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org
Subject: Re: [PATCHv3 RFC] virtio-pci: flexible configuration layout
On Wed, 2011-11-23 at 13:02 +1030, Rusty Russell wrote:
> On Tue, 22 Nov 2011 20:36:22 +0200, "Michael S. Tsirkin" <mst@...hat.com> wrote:
> > Here's an updated vesion.
> > I'm alternating between updating the spec and the driver,
> > spec update to follow.
>
> Don't touch the spec yet, we have a long way to go :(
>
> I want the ability for driver to set the ring size, and the device to
> set the alignment. That's a bigger change than you have here. I
> imagine it almost rips the driver into two completely different drivers.
>
> This is the kind of thing I had in mind, for the header. Want me to
> code up the rest?
>
> (I've avoided adding the constants for the new layout: a struct is more
> compact and more descriptive).
>
> Cheers,
> Rusty.
>
> diff --git a/include/linux/virtio_pci.h b/include/linux/virtio_pci.h
> --- a/include/linux/virtio_pci.h
> +++ b/include/linux/virtio_pci.h
> @@ -42,56 +42,74 @@
> #include <linux/virtio_config.h>
>
> /* A 32-bit r/o bitmask of the features supported by the host */
> -#define VIRTIO_PCI_HOST_FEATURES 0
> +#define VIRTIO_PCI_LEGACY_HOST_FEATURES 0
>
> /* A 32-bit r/w bitmask of features activated by the guest */
> -#define VIRTIO_PCI_GUEST_FEATURES 4
> +#define VIRTIO_PCI_LEGACY_GUEST_FEATURES 4
>
> /* A 32-bit r/w PFN for the currently selected queue */
> -#define VIRTIO_PCI_QUEUE_PFN 8
> +#define VIRTIO_PCI_LEGACY_QUEUE_PFN 8
>
> /* A 16-bit r/o queue size for the currently selected queue */
> -#define VIRTIO_PCI_QUEUE_NUM 12
> +#define VIRTIO_PCI_LEGACY_QUEUE_NUM 12
>
> /* A 16-bit r/w queue selector */
> -#define VIRTIO_PCI_QUEUE_SEL 14
> +#define VIRTIO_PCI_LEGACY_QUEUE_SEL 14
>
> /* A 16-bit r/w queue notifier */
> -#define VIRTIO_PCI_QUEUE_NOTIFY 16
> +#define VIRTIO_PCI_LEGACY_QUEUE_NOTIFY 16
>
> /* An 8-bit device status register. */
> -#define VIRTIO_PCI_STATUS 18
> +#define VIRTIO_PCI_LEGACY_STATUS 18
>
> /* An 8-bit r/o interrupt status register. Reading the value will return the
> * current contents of the ISR and will also clear it. This is effectively
> * 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
> +#define VIRTIO_PCI_LEGACY_ISR 19
>
> /* MSI-X registers: only enabled if MSI-X is enabled. */
> /* A 16-bit vector for configuration changes. */
> -#define VIRTIO_MSI_CONFIG_VECTOR 20
> +#define VIRTIO_MSI_LEGACY_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
> +#define VIRTIO_MSI_LEGACY_QUEUE_VECTOR 22
>
> /* The remaining space is defined by each driver as the per-driver
> * configuration space */
> -#define VIRTIO_PCI_CONFIG(dev) ((dev)->msix_enabled ? 24 : 20)
> +#define VIRTIO_PCI_LEGACY_CONFIG(dev) ((dev)->msix_enabled ? 24 : 20)
> +
> +/* How many bits to shift physical queue address written to QUEUE_PFN.
> + * 12 is historical, and due to x86 page size. */
> +#define VIRTIO_PCI_LEGACY_QUEUE_ADDR_SHIFT 12
> +
> +/* The alignment to use between consumer and producer parts of vring.
> + * x86 pagesize again. */
> +#define VIRTIO_PCI_LEGACY_VRING_ALIGN 4096
> +
> +#ifndef __KERNEL__
> +/* Don't break compile of old userspace code. These will go away. */
Maybe wrap it in:
#ifndef VIRTIO_PCI_NO_LEGACY
#warning Please stop using old defines
[...]
> +#define VIRTIO_PCI_HOST_FEATURES VIRTIO_PCI_LEGACY_HOST_FEATURES
> +#define VIRTIO_PCI_GUEST_FEATURES VIRTIO_PCI_LEGACY_GUEST_FEATURES
> +#define VIRTIO_PCI_LEGACY_QUEUE_PFN VIRTIO_PCI_QUEUE_PFN
> +#define VIRTIO_PCI_LEGACY_QUEUE_NUM VIRTIO_PCI_QUEUE_NUM
> +#define VIRTIO_PCI_LEGACY_QUEUE_SEL VIRTIO_PCI_QUEUE_SEL
> +#define VIRTIO_PCI_LEGACY_QUEUE_NOTIFY VIRTIO_PCI_QUEUE_NOTIFY
> +#define VIRTIO_PCI_LEGACY_STATUS VIRTIO_PCI_STATUS
> +#define VIRTIO_PCI_LEGACY_ISR VIRTIO_PCI_ISR
> +#define VIRTIO_MSI_LEGACY_CONFIG_VECTOR VIRTIO_MSI_CONFIG_VECTOR
> +#define VIRTIO_MSI_LEGACY_QUEUE_VECTOR VIRTIO_MSI_QUEUE_VECTOR
> +#define VIRTIO_PCI_LEGACY_CONFIG(dev) VIRTIO_PCI_CONFIG(dev)
> +#define VIRTIO_PCI_LEGACY_QUEUE_ADDR_SHIFT VIRTIO_PCI_QUEUE_ADDR_SHIFT
> +#define VIRTIO_PCI_LEGACY_VRING_ALIGN VIRTIO_PCI_VRING_ALIGN
#endif /* VIRTIO_PCI_NO_LEGACY */
> +#endif /* ...!KERNEL */
>
> /* Virtio ABI version, this must match exactly */
> #define VIRTIO_PCI_ABI_VERSION 0
>
> -/* How many bits to shift physical queue address written to QUEUE_PFN.
> - * 12 is historical, and due to x86 page size. */
> -#define VIRTIO_PCI_QUEUE_ADDR_SHIFT 12
> +/* Vector value used to disable MSI for queue */
> +#define VIRTIO_MSI_NO_VECTOR 0xffff
>
> -/* The alignment to use between consumer and producer parts of vring.
> - * x86 pagesize again. */
> -#define VIRTIO_PCI_VRING_ALIGN 4096
> +/* The bit of the ISR which indicates a device configuration change. */
> +#define VIRTIO_PCI_ISR_CONFIG 0x2
>
> /*
> * Layout for Virtio PCI vendor specific capability (little-endian):
> @@ -133,4 +151,20 @@
> #define VIRTIO_PCI_CAP_CFG_OFF_MASK 0xffffffff
> #define VIRTIO_PCI_CAP_CFG_OFF_SHIFT 0
>
> +/* Fields in VIRTIO_PCI_CAP_COMMON_CFG: */
> +struct virtio_pci_common_cfg {
> + /* About the whole device. */
> + __u64 device_features; /* read-only */
> + __u64 guest_features; /* read-write */
> + __u64 queue_address; /* read-write */
queue address should be in the queue specific fields below
> + __u16 msix_config; /* read-write */
> + __u8 device_status; /* read-write */
> + __u8 unused;
> +
> + /* About a specific virtqueue. */
> + __u16 queue_select; /* read-write */
> + __u16 queue_align; /* read-write, power of 2. */
> + __u16 queue_size; /* read-write, power of 2. */
> + __u16 queue_msix_vector;/* read-write */
Maybe we should reserve a bunch of bytes here for future extensions of
virtqueues. Otherwise, non virtqueue options may be added here which
will cause fragmentation of virtqueue specific features.
> +};
> #endif
>
>
>
--
Sasha.
--
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