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Re: Feedback on multi-process QEMU muser prototype
From: |
Stefan Hajnoczi |
Subject: |
Re: Feedback on multi-process QEMU muser prototype |
Date: |
Mon, 20 Jan 2020 10:41:03 +0000 |
On Wed, Jan 15, 2020 at 10:58:38AM +0000, Felipe Franciosi wrote:
> > On Jan 14, 2020, at 3:22 PM, Stefan Hajnoczi <address@hidden> wrote:
> >
> > I haven't seen the link to the muser prototype shared on the list yet,
> > so I'm taking the liberty of posting it for discussion:
> > https://github.com/oracle/qemu/tree/multi-process-qemu-v0.4.1-muser
> >
> > Great that a lot of the multi-process patch series is no longer
> > necessary. The muser approach requires less code in QEMU.
> >
> > The following points came to mind:
> >
> > 1. Configure PCI configuration space, BARs, and MSI/IRQs based on the
> > PCIDevice
> > instead of hard-coding the LSI SCSI controller's specifics. That way any
> > PCIDevice can run as an muser device.
> >
> > 2. Integrate with QEMU's event loop instead of spawning threads and calling
> > lm_ctx_run(). The event loop should monitor the muser fd for activity
> > using
> > aio_set_fd_handler() and then call into libmuser to handle the event.
> > This
> > will avoid thread model problems in the future and also allow true
> > multi-threading (IOThreads).
>
> Allowing muser to be used like that is in our to-do list.
>
> (+ Thanos / Swapnil).
>
> We have to extend muser.ko to allow the device file descriptor to be
> "pollable". Let me know how soon you want to see that so we can
> prioritise accordingly or assist someone in doing the work.
Last I talked with the multi-process QEMU team the discussion was about
moving forward with the existing QEMU patches and then moving to
VFIO-over-socket. libmuser makes a nice library API for device emulator
programs and I think it will be revisited when VFIO-over-socket
integration begins.
This makes the pollable fd less of a priority for QEMU at the moment.
Stefan
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