|
From: | Avi Kivity |
Subject: | [Qemu-devel] Re: [PATCH] Inter-VM shared memory PCI device |
Date: | Thu, 11 Mar 2010 08:49:08 +0200 |
User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.8) Gecko/20100301 Fedora/3.0.3-1.fc12 Thunderbird/3.0.3 |
On 03/10/2010 06:36 PM, Cam Macdonell wrote:
On Wed, Mar 10, 2010 at 2:21 AM, Avi Kivity<address@hidden> wrote:On 03/09/2010 08:34 PM, Cam Macdonell wrote:On Tue, Mar 9, 2010 at 10:28 AM, Avi Kivity<address@hidden> wrote:On 03/09/2010 05:27 PM, Cam Macdonell wrote:Registers are used for synchronization between guests sharing the same memory object when interrupts are supported (this requires using the shared memory server).How does the driver detect whether interrupts are supported or not?At the moment, the VM ID is set to -1 if interrupts aren't supported, but that may not be the clearest way to do things. With UIO is there a way to detect if the interrupt pin is on?I suggest not designing the device to uio. Make it a good guest-independent device, and if uio doesn't fit it, change it. Why not support interrupts unconditionally? Is the device useful without interrupts?Currently my patch works with or without the shared memory server. If you give the parameter -ivshmem 256,foo then this will create (if necessary) and map /dev/shm/foo as the shared region without interrupt support. Some users of shared memory are using it this way. Going forward we can require the shared memory server and always have interrupts enabled.Can you explain how they synchronize? Polling? Using the network? Using it as a shared cache? If it's a reasonable use case it makes sense to keep it.Do you mean how they synchronize without interrupts? One project I've been contacted about uses the shared region directly for synchronization for simulations running in different VMs that share data in the memory region. In my tests spinlocks in the shared region work between guests.
I see.
If we want to keep the serverless implementation, do we need to support shm_open with -chardev somehow? Something like -chardev shm,name=foo. Right now my qdev implementation just passes the name to the -device option and opens it.
I think using the file name is fine.
Another thing comes to mind - a shared memory ID, in case a guest has multiple cards.Sure, a number that can be passed on the command-line and stored in a register?
Yes. NICs use the MAC address and storage uses the disk serial number, this is the same thing for shared memory.
-- error compiling committee.c: too many arguments to function
[Prev in Thread] | Current Thread | [Next in Thread] |