[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] PVHVM drivers in upstream linux kernel

On 12/02/2014 12:36 PM, Ian Campbell wrote:
On Tue, 2014-12-02 at 12:33 +0100, Juergen Gross wrote:
On 12/02/2014 12:05 PM, Ian Campbell wrote:
On Tue, 2014-12-02 at 10:54 +0000, David Vrabel wrote:
On 02/12/14 09:39, Juergen Gross wrote:

looking into the upstream linux sources I realized that the PVHVM
drivers of XEN are only available with the pvops kernel. Is this on
purpose? Shouldn't the frontend drivers, xen/platform-pci.c etc. be
configurable without having to enable CONFIG_PARAVIRT?

I suppose that would be possible but I don't think it's a useful
configuration because you would lose PV spinlocks for example.

IIRC the reason this hasn't been implemented until now is that
refactoring would be required to the various bits of driver code which
assumes PAE + PARAVIRT when they aren't strictly needed, e.g. grant
table code. Whether its worth the churn at this stage is debatable, but
I think the (in)ability to use PV spinlocks is a red-herring.

Adding PV drivers to an HVM guest is a useful thing to do, even without
PV spinlocks. PV IO gets you far more incremental benefit than the locks
do, adding PV IO paths is the number 1 thing which should be done to any

I take this as an "ack" to change this. :-)

It's a best "IMHO being able to do this is a useful thing". I can't ack
the actual final patch, a) I'm not a relevant maintainer and b) I've not
seen the patch.

It was not meant to be taken as an ack for a not yet written patch. :-)

Okay, how do the current config settings regarding Xen look like?

...I'll leave the mechanics down to you and the maintainers to thrash

Yeah, stay tuned. :-)


Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.