[EXTERNAL] Re: [RFC PATCH v1] powerpc/prom_init: disable XIVE in Secure VM.

Greg Kurz groug at kaod.org
Wed Mar 4 19:34:44 AEDT 2020


On Tue, 3 Mar 2020 20:18:18 +0100
Cédric Le Goater <clg at kaod.org> wrote:

> >> **** BTW: I figured, I dont need this intermin patch to disable xive for
> >> secure VM.  Just doing "svm=on xive=off" on the kernel command line is
> >> sufficient for now. *****
> >>
> > 
> > No it is not. If the hypervisor doesn't propose XIVE (ie. ic-mode=xive
> > on the QEMU command line), the kernel simply ignores "xive=off".
> 

Ah... sorry for the typo... "doesn't propose XICS" of course :)

> If I am correct, with the option ic-mode=xive, the hypervisor will 
> propose only 'xive' in OV5 and not both 'xive' and 'xics'. But the
> result is the same because xive can not be turned off and "xive=off" 
> is ignored.
> 
> Anyway, it's not the most common case of usage of the QEMU command
> like. I think it's OK to use "xive=off" on the kernel command line 
> for now.
> 

Sure, I just wanted to make things clear. Like you said it's a chicken
switch introduced for distro testing. I think it should not be used
to do anything else. If "svm=1" needs to enforce supported.xive == false
as a temporary workaround, it should do it explicitly.

> C.



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