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Re: [Qemu-devel] Would virtio support 64 bit address for vring virtqueue
From: |
Anthony Liguori |
Subject: |
Re: [Qemu-devel] Would virtio support 64 bit address for vring virtqueue? |
Date: |
Wed, 28 Aug 2013 16:28:38 -0500 |
On Wed, Aug 28, 2013 at 4:02 PM, H. Peter Anvin <address@hidden> wrote:
> On 08/28/2013 10:35 AM, Anthony Liguori wrote:
>> Yes, it was originally designed with the 16TB limit in mind.
>>
>> PCI doesn't support 64-bit PIO operations so it would have required a
>> high/low register and additional magic.
>>
>
> s/PCI/x86/
Ack. Although I wonder if there is a device out there that actually
expects 64-bit writes to a register in an PIO region...
> "Additional magic" is needed only if atomic changes are necessary, but
> in this case this is stuff that is set up during early configuration and
> so isn't an issue. The "additional magic" needed in that case is latch
> logic - the write to the low part doesn't actually take effect until the
> high part is written.
Well in this case, writing to the PFN is what causes the queue to be
initialized, there isn't a separate status register for this purpose.
Since it's a PIO region, we tried hard to keep the common case within
a 32-byte region and since config space is after the virtio-pci
registers, we tried to keep it as small as possible to maximize
available config space.
Regards,
Anthony Liguori
>
> -hpa
>
- [Qemu-devel] Would virtio support 64 bit address for vring virtqueue?, Xie, Huawei, 2013/08/27
- Re: [Qemu-devel] Would virtio support 64 bit address for vring virtqueue?, Stefan Hajnoczi, 2013/08/28
- Re: [Qemu-devel] Would virtio support 64 bit address for vring virtqueue?, Xie, Huawei, 2013/08/28
- Re: [Qemu-devel] Would virtio support 64 bit address for vring virtqueue?, Laszlo Ersek, 2013/08/28
- Re: [Qemu-devel] Would virtio support 64 bit address for vring virtqueue?, Christian Borntraeger, 2013/08/28
- Re: [Qemu-devel] Would virtio support 64 bit address for vring virtqueue?, Xie, Huawei, 2013/08/28
- Re: [Qemu-devel] Would virtio support 64 bit address for vring virtqueue?, Anthony Liguori, 2013/08/28
- Re: [Qemu-devel] Would virtio support 64 bit address for vring virtqueue?, H. Peter Anvin, 2013/08/28
- Re: [Qemu-devel] Would virtio support 64 bit address for vring virtqueue?,
Anthony Liguori <=
- Re: [Qemu-devel] Would virtio support 64 bit address for vring virtqueue?, Richard Henderson, 2013/08/28
Re: [Qemu-devel] Would virtio support 64 bit address for vring virtqueue?, Xie, Huawei, 2013/08/28