Re: PCI passthrough with stubdomain

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

[-- Attachment #1.1: Type: text/plain, Size: 1719 bytes --]

On Fri, Sep 23, 2016 at 04:51:33PM +0200, Samuel Thibault wrote:
> Marek Marczykowski-Górecki, on Fri 23 Sep 2016 16:25:41 +0200, wrote:
> > Toolstack during (stub)domain startup setup two things, mostly
> > asynchronously:
> > 1. pciback/pcifront (through standard xenstore entries)
> > 2. instruct qemu to attach device (by writing "pci-ins" to
> > device-model/xxx/command)
> 
> Ah, since pcifront_watches runs in a separate thread, it may not have
> called init_pcifront before qemu calls libpci, i.e. pcifront_scan.

Yes, exactly.

> I'd say that's where the fix should be: make pcifront_scan wait for
> init_pcifront to be done.  It's however not so simple: we want to make
> pcifront_scan do nothing if no pciback is to be launched. My memory is
> rusty: is there something we are sure will show up in the xenstore when
> a pciback is to be launched?  If so, pcifront_scan could do this: wait
> for pcifront_watches to have checked for the potential presence of
> pciback. If pciback is not to be started, just do nothing; if pciback is
> to be started, wait for init_pcifront to have been called by
> pcifront_watches. Then it will find the devices.

Ok. So, two questions:
1. How to do this? ;) I.e. what synchronization primitives are available
in mini-os? Just pthread_mutex_lock/unlock?

2. Wouldn't the same problem be with other stubdomain implementations?
Like Linux + qemu-xen or rumprun + qemu-xen? At least in Linux case
pcifront driver will also needs some time for initialization...

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 473 bytes --]

[-- Attachment #2: Type: text/plain, Size: 127 bytes --]

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel