[Qemu-devel] virtio documentation or BSD licensed driver?

[Qemu-devel] virtio documentation or BSD licensed driver?

[higepon]

Hi.

I'm developer of Mona OS (http://www.monaos.org).
Mona OS is testd and ran on QEMU.

We have a plan to implement virtio_net driver for our OS.
Since Mona OS is MIT/X license, we can't use or see Linux's virtio drivers.

Is there any
- interface documentation for virtio?
- BSD licensed drivers?

Best regards,

---
MINOWA Taro(Higepon)

http://www.monaos.org/
http://code.google.com/p/mosh-scheme/
http://www.facebook.com/people/Taro_Minowa_Higepon/649065487
http://friendfeed.com/higepon

Re: [Qemu-devel] virtio documentation or BSD licensed driver?

[Brian Jackson]

There's some on the Documents page of the kvm wiki. The virtio code  
walkthrough actually doesn't have any code in it. The other docs do.  
The ACM pdf is actually very informative, but does include some code  
snippets from the headers. I don't know what license the header code  
is under.

Fwiw, I don't know how much virtio will buy you over the e1000  
emulation.



On May 3, 2009, at 11:05 PM, higepon wrote:

> Hi.
>
> I'm developer of Mona OS (http://www.monaos.org).
> Mona OS is testd and ran on QEMU.
>
> We have a plan to implement virtio_net driver for our OS.
> Since Mona OS is MIT/X license, we can't use or see Linux's virtio  
> drivers.
>
> Is there any
> - interface documentation for virtio?
> - BSD licensed drivers?
>
> Best regards,
>
> ---
> MINOWA Taro(Higepon)
>
> http://www.monaos.org/
> http://code.google.com/p/mosh-scheme/
> http://www.facebook.com/people/Taro_Minowa_Higepon/649065487
> http://friendfeed.com/higepon
>
>

Re: [Qemu-devel] virtio documentation or BSD licensed driver?

[higepon]

Hi. Thank you.

> There's some on the Documents page of the kvm wiki.

I found this page and attached pdf.
http://www.linux-kvm.org/page/Virtio

But not enough.

> The ACM
> pdf is actually very informative, but does include some code snippets from
> the headers. I don't know what license the header code is under.

It's good document.
And as far as I know Linux's virio headers are BSD licensed.

> Fwiw, I don't know how much virtio will buy you over the e1000 emulation.

Sure.
I want to compare and choose which to use and implement.

I still need more documents, if anybody knows please let me know.

Cheers.


On Mon, May 4, 2009 at 1:21 PM, Brian Jackson <iggy@theiggy.com> wrote:
> There's some on the Documents page of the kvm wiki. The virtio code
> walkthrough actually doesn't have any code in it. The other docs do. The ACM
> pdf is actually very informative, but does include some code snippets from
> the headers. I don't know what license the header code is under.
>
> Fwiw, I don't know how much virtio will buy you over the e1000 emulation.
>
>
>
> On May 3, 2009, at 11:05 PM, higepon wrote:
>
>> Hi.
>>
>> I'm developer of Mona OS (http://www.monaos.org).
>> Mona OS is testd and ran on QEMU.
>>
>> We have a plan to implement virtio_net driver for our OS.
>> Since Mona OS is MIT/X license, we can't use or see Linux's virtio
>> drivers.
>>
>> Is there any
>> - interface documentation for virtio?
>> - BSD licensed drivers?
>>
>> Best regards,
>>
>> ---
>> MINOWA Taro(Higepon)
>>
>> http://www.monaos.org/
>> http://code.google.com/p/mosh-scheme/
>> http://www.facebook.com/people/Taro_Minowa_Higepon/649065487
>> http://friendfeed.com/higepon
>>
>>
>
>

Re: [Qemu-devel] virtio documentation or BSD licensed driver?

[Pantelis Koukousoulas]

>>> Is there any
>>> - interface documentation for virtio?
>>> - BSD licensed drivers?

Virtio was designed as a Linux API AFAIK (nothing prevents it from
being ported of course).
So, the most useful info should be in the (BSD Licensed) headers. The
actual virtio-net driver
code will not be very helpful to someone unfamilliar with the way
Linux does things (e.g.,
skbs, ethernet operations etc etc). If you want to port virtio-net to
another OS though, you
will have to provide the infrastructure too, so you have 2 choices:

1) Implement it like in Linux in 4 layers: virtio_pci, virtio_ring,
virtio (virtqueues etc), virtio_net.

2) Think of virtio-net as just another (sophisticated) PCI driver and
look at its implemenation
in qemu. Although qemu is not BSD licensed, your work is unlikely to
be considered a derivative
of qemu since you are implementing a driver for that virtual
"hardware", not another copy it.

The BSD virtio headers, the paper and the virtio-net qemu
implementation should be enough to
allow you to write a driver for your OS imho (it is already more info
than you typically get for
real hardware)

Pantelis

P.S., in practice I believe several developers for other OSes look at
the sources of linux drivers
as sort of a really good documentation for hardware, even if the
license of their OS is incompatible.
IANAL and all that, but I 'd be really suprised if you got sued for
porting virtio-net to your hobby OS :)

(E.g., there are currently closed-source windows virtio-net drivers
and nobody cared to request an
audit whether they are a derivative of the Linux drivers or not).

Re: [Qemu-devel] virtio documentation or BSD licensed driver?

[higepon]

Hi.

I really appreciate your help. Thanks.
That's what I want to know about.

> 2) Think of virtio-net as just another (sophisticated) PCI driver and
> look at its implemenation
> in qemu. Although qemu is not BSD licensed, your work is unlikely to
> be considered a derivative
> of qemu since you are implementing a driver for that virtual
> "hardware", not another copy it.

Maybe this is suitable for my OS.

> The BSD virtio headers, the paper and the virtio-net qemu
> implementation should be enough to
> allow you to write a driver for your OS imho (it is already more info
> than you typically get for
> real hardware)

Okay I will start from reading the paper.

> P.S., in practice I believe several developers for other OSes look at
> the sources of linux drivers
> as sort of a really good documentation for hardware, even if the
> license of their OS is incompatible.
> IANAL and all that, but I 'd be really suprised if you got sued for
> porting virtio-net to your hobby OS :)

Interesting and resonable.
But Since Mona OS is my life work, i want to avoid from license problems.


Cheers.

Re: [Qemu-devel] virtio documentation or BSD licensed driver?

[higepon]

Hi.

With your kind advice,
finally I succeeded in writing to virtio-console on QEMU from my OS.

But there are a few things I don't understand about vring_avail struct.
On Rusty Russell's article "virtio: Towards a De-Facto Standard For
Virtual I/O Devices".

He explained like following.

struct vring_avail
{
__u16 flags;
__u16 idx;
__u16 ring[NUM];
};

> The available ring consists of a free-running index, an interrupt
> suppression flag, and an array of indices into the
> descriptor table (representing the heads of buffers).

(1) What does it mean "free-running index"?
    And what value guest should set to idx? The index of head of
available descriptor?

(2) What value guest should set to ring[NUM].

I've Googled these things, but there are few documents about them.

Here is my whole code.
If I did something wrong, I appreciate your pointing me out.

int main(int argc, char* argv[])
{
    // 1. Device probe
    PciInf pciInf;
    Pci pci;
    pci.CheckPciExist(PCI_VENDOR_ID_REDHAT_QUMRANET,
PCI_DEVICE_ID_VIRTIO_CONSOLE, &pciInf);

    if (!pciInf.isExist) {
        printf("device not found\n");
        exit(-1);
    }

    printf("device found\n");
    printf("baseAdress=%x\n", pciInf.baseAdress);
    printf("irqLine=%x\n", pciInf.irqLine);

    const uintptr_t baseAddress = pciInf.baseAdress & ~1;

    // 2. reset the device
    outp8(baseAddress + VIRTIO_PCI_STATUS, 0); // 0: reset
    printf("[virtio] isr=%x\n", inp8(baseAddress + VIRTIO_PCI_ISR));
// clear ISR.

    // 3. IRQ receiver
    monapi_set_irq(pciInf.irqLine, MONAPI_TRUE, MONAPI_TRUE);
    syscall_set_irq_receiver(pciInf.irqLine, SYS_MASK_INTERRUPT);

    // 4. Select the queue to use
    outp16(baseAddress + VIRTIO_PCI_QUEUE_SEL, 1); // 0: read queue,
1: write queue

    // 5. how many descriptors do the queue have?
    const int numberOfDesc = inp16(baseAddress + VIRTIO_PCI_QUEUE_NUM);
    printf("[virtio] numberOfDesc=%d\n", numberOfDesc);
    ASSERT(numberOfDesc > 0);

    // 6. Check wheter the queue is already set vring (necessary?).
    uint16_t pfn = inp16(baseAddress + VIRTIO_PCI_QUEUE_PFN);
    if (pfn != 0) {
        printf("[virtio] pfn=%x\n", pfn);
        exit(-1);
    }

    // 7. setup vring
    const int MAX_QUEUE_SIZE = PAGE_MASK + vring_size(MAX_QUEUE_NUM);
    printf("[virtio] MAX_QUEUE_SIZE=%d\n", MAX_QUEUE_SIZE);
    uint8_t queueData[MAX_QUEUE_SIZE];
    memset(queueData, 0, MAX_QUEUE_SIZE);

    struct vring vring;
    vring.num = numberOfDesc;

    // page align is required
    const uintptr_t physicalAddress =
syscall_get_physical_address((uintptr_t)queueData, NULL);
    printf("[virtio] physicalAddress=%x\n", physicalAddress);
    const uintptr_t alignedAddress = (physicalAddress + PAGE_MASK) & ~PAGE_MASK;
    printf("[virtio] alignedAddress=%x\n", alignedAddress);

    ASSERT((alignedAddress % PAGE_SIZE) == 0);

    // vring.desc is page aligned
    vring.desc = (struct vring_desc*)(queueData + alignedAddress -
physicalAddress);

    // make linked ring
    for (uintptr_t i = 0; i < vring.num; i++) {
        vring.desc[i].next = i + 1;
    }
    vring.desc[vring.num - 1].next = 0;

    // vring.avail is follow after the array of desc
    vring.avail = (struct vring_avail *)&vring.desc[numberOfDesc];

    // vring.used is also page aligned
    const uintptr_t usedPhysicalAddress =
syscall_get_physical_address((uintptr_t)&(vring.avail->ring[numberOfDesc]),
NULL);
    const uintptr_t usedAligendAddress = (usedPhysicalAddress +
PAGE_MASK) & ~PAGE_MASK;
    ASSERT((usedAligendAddress % PAGE_SIZE) == 0);
    vring.used = (struct
vring_used*)((uintptr_t)&(vring.avail->ring[numberOfDesc]) +
usedAligendAddress - usedPhysicalAddress);

    // 9. set up pfn
    printf("[virtio] set up PFN\n");
    outp32(baseAddress + VIRTIO_PCI_QUEUE_PFN,
syscall_get_physical_address((uintptr_t)vring.desc, NULL) >> 12);

    // 10. prepare the data to write
    uint8_t data[PAGE_SIZE * 2];
    const uintptr_t phys = syscall_get_physical_address((uintptr_t)data, NULL);
    const uintptr_t aphys = (phys+ PAGE_MASK) & ~PAGE_MASK;
    char* p = (char*) (data + aphys - phys);
    strcpy(p, "Hello, World");

    // 11. set the data to vring
    vring.desc[0].flags = 0; // no next
    vring.desc[0].addr = syscall_get_physical_address((uintptr_t)p, NULL);
    vring.desc[0].len = strlen(p) + 1;
    vring.avail->idx = 1; // ??????

    // 12. Notify!
    printf("[virtio] vring.used->idx = %d \n", vring.used->idx);
    outp16(baseAddress + VIRTIO_PCI_QUEUE_NOTIFY, 1);

    // 13. wait notification from host
    MessageInfo msg;
    Message::receive(&msg);

    switch (msg.header)
    {
    case MSG_INTERRUPTED:
    {
        printf("[virtio] Interrupt comes\n");
        // clear ISR.
        const uint8_t isr = inp8(baseAddress + VIRTIO_PCI_ISR);
        printf("[virtio] isr=%x\n", isr);
        monapi_set_irq(pciInf.irqLine, MONAPI_TRUE, MONAPI_TRUE);
        break;
    }
    default:
        printf("[virtio] uknown message\n");
        break;
    }

    // if data is written, idx 0 => 1
    printf("[virtio] vring.used->idx = %d \n", vring.used->idx);
}

Cheers.


On Mon, May 4, 2009 at 7:36 PM, higepon <higepon@gmail.com> wrote:
> Hi.
>
> I really appreciate your help. Thanks.
> That's what I want to know about.
>
>> 2) Think of virtio-net as just another (sophisticated) PCI driver and
>> look at its implemenation
>> in qemu. Although qemu is not BSD licensed, your work is unlikely to
>> be considered a derivative
>> of qemu since you are implementing a driver for that virtual
>> "hardware", not another copy it.
>
> Maybe this is suitable for my OS.
>
>> The BSD virtio headers, the paper and the virtio-net qemu
>> implementation should be enough to
>> allow you to write a driver for your OS imho (it is already more info
>> than you typically get for
>> real hardware)
>
> Okay I will start from reading the paper.
>
>> P.S., in practice I believe several developers for other OSes look at
>> the sources of linux drivers
>> as sort of a really good documentation for hardware, even if the
>> license of their OS is incompatible.
>> IANAL and all that, but I 'd be really suprised if you got sued for
>> porting virtio-net to your hobby OS :)
>
> Interesting and resonable.
> But Since Mona OS is my life work, i want to avoid from license problems.
>
>
> Cheers.
>