Re: [Xen-ia64-devel] pv_ops: entry.S simplification

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

Oh, I misunderstood your patch.
I thought it just revert entry.S to original state. But it
paravirtualized conver and rfi with running_on_xen check.
Now I'm convinced that your patch works. Only one comment on
the patch itself is, 
#ifdef CONFIG_XEN is necessary for !CONFIG_XEN case.


Then the left issue is 'if the patch is acceptable for the upstream'.
The purpose of reducing the total patch size is eventually
to make ia64/xen domU patches more acceptable for the upstream.
However with the patch you reintroduced running_on_xen check which
we have eliminted. That contradicts with the pv_ops principle.
It's a trade off between the patch size and the patch cleanness.

Eventually those running_on_xen checks should be removed somehow.
Are you just thinking that the multi compile with binary patching
should be introduced after the first merge?
Or do you have any idea other than the multi compile with binary patching?


Anyway it's linux-ia64 people that finally determines what way is
better. To be honest I'm not sure which way is more acceptable.
So let's discuss with linux-ia64. 


On Thu, Mar 27, 2008 at 05:04:21PM +0800, Dong, Eddie wrote:
> Isaku Yamahata wrote:
> > Hi Eddie.
> > 
> > I looked into entry.S closely.
> > Unfortunately I found that ia64_leave_syscall() and
> > ia64_leave_kernel() includes invirtualizable instructions,
> > cover instruction with psr.ic = 0 so that those paravirtualization
> > is inevitable. (ia64_switch_to() doesn't need paravirtualization
> > though.) 
> 
> Yes there 2 kind of instructions we must modify, one is cover when
> psr.ic=0, another one is RFI which can;t be handled by Xen today.
> 
> But I temply put running on xen for now, I am working on using 
> indirect function call pv_ops now.
> 
> Or do you mean there are still missed "cover" instruction?
> 
> > 
> > Does it really work? Probably "just seeing login prompt test" doesn't
> > reveal the issues.
> > 
> > thanks,
> > 
> 
> I can login and do minimal ops, I didn't take stress test.
> But in my coding time, if a cover with PSR.ic=0 is missed,
> or RFI is missed, guest will soon die.
> 
> Thanks, eddie
> 
> _______________________________________________
> Xen-ia64-devel mailing list
> Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-ia64-devel
> 

-- 
yamahata

_______________________________________________
Xen-ia64-devel mailing list
Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-ia64-devel