RE: [Xen-ia64-devel] [PATCH] Fix weird dom0 behavior due to incorrentkr emulation

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

Committed.

I am very sorry that you are finding bugs in my KR code.
These would never have been checked in if we had a running
multiple domain test suite... the existing "compile
Linux many times on domain0" is clearly inadequate.

Fred, any progress on the test suite?

Thanks,
Dan

> -----Original Message-----
> From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf 
> Of Tian, Kevin
> Sent: Tuesday, November 01, 2005 7:31 AM
> To: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-ia64-devel] [PATCH] Fix weird dom0 behavior due 
> to incorrentkr emulation
> 
> Then, this is another easy-fix but hard-won issue which spent 
> me most of
> the day to track down.
> 
> The phenomenon is very weird. Dom0 can run pretty well 
> itself, but once
> creating another domain, I saw dom0 falling into nested fault or panic
> being unable to handle kernel paging request. The worst is, dom0 even
> used user stack like 0x60000ffff... in kernel space. That made me
> confused why dom0 doesn't switch stack though I confirmed 
> vIIP actually
> from user space.
> 
> Finally the cause is intuitive as the attached patch. All writes to
> KR0-7 by guest are pushed to same place (vkr0) in shared page 
> including
> important current pointer. Because domain owns physical KRs, those
> writes will also be updated into physical KRs. If there's no domain
> switch, dom0 always read from physical KRs which contain right values.
> Only after switching back to dom0, last KR patch will try to reload
> physical KRs from shared page and however that memory area contains
> incorrect values. So later execution flow went crazy by checking
> incorrect current pointer.
> 
> Signed-off-by Kevin Tian <Kevin.tian@xxxxxxxxx>
> 
> Thanks,
> Kevin
> 

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