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[Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device
From: |
Cam Macdonell |
Subject: |
[Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device |
Date: |
Thu, 25 Mar 2010 17:05:38 -0600 |
On Thu, Mar 25, 2010 at 3:10 PM, Avi Kivity <address@hidden> wrote:
> On 03/25/2010 08:17 PM, Cam Macdonell wrote:
>>
>>>> I had a hunch it was probably considered. That explains why irqfd
>>>> doesn't have a datamatch field. I guess supporting multiple MSI
>>>> vectors with one doorbell per guest isn't possible if one 1 bit of
>>>> information can be communicated.
>>>>
>>>>
>>>
>>> Actually you can have one doorbell supporting multiple vectors and
>>> guests,
>>> simply divide the data value into two bit fields, one for the vector and
>>> one
>>> for the guest. A single write gets both values into the host, which can
>>> then use datamatch to trigger the correct eventfd (which is wired to an
>>> irqfd in another guest).
>>>
>>
>> At 4-bits per guest, a single write is then limited to 8 guests (with
>> 32-bit registers), we could got to 64-bit.
>>
>
> I meant a unicast doorbell: 16 bits for guest ID, 16 bits for vector number.
Ah, yes. Who knew "two bit registers" is an ambiguous term. Do you
strongly prefer the one doorbell design?
- [Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device, (continued)
- [Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device, Michael S. Tsirkin, 2010/03/25
- [Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device, Markus Armbruster, 2010/03/25
- [Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device, Cam Macdonell, 2010/03/25
- [Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device, Avi Kivity, 2010/03/25
- [Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device, Cam Macdonell, 2010/03/25
- [Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device, Avi Kivity, 2010/03/25
- [Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device, Cam Macdonell, 2010/03/25
- [Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device, Avi Kivity, 2010/03/25
- [Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device,
Cam Macdonell <=
- [Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device, Avi Kivity, 2010/03/26
- Re: [Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device, Jamie Lokier, 2010/03/25
- Re: [Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device, Cam Macdonell, 2010/03/26