[Xen-devel] Re: [PATCH 01/04] Kexec / Kdump: Generic code

[Horms <horms@xxxxxxxxxxxx>]

On Wed, Oct 18, 2006 at 08:15:45AM +0100, Keir Fraser wrote:
> On 18/10/06 2:00 am, "Horms" <horms@xxxxxxxxxxxx> wrote:
> 
> >> Yes please. This isn't performance critical. Folding will make the 
> >> interface
> >> better match other hypercalls.
> > 
> > The main thing that I am concerned about is, that in the
> > case that dom0 panics, and we are asking the hypercall to take a dump
> > for us, do we really want a copy_from guest in that path?
> > It seems to me that its best to have that path as simple as possible.
> > But I do argree that it comes at the expense of making the interface
> > a bit unclean.
> 
> We need to assume that kernel address space hasn't been too badly
> compromised, or we couldn't execute as far as making the hypercall. A failed
> copy_from_guest() in the crash hypercall could simply cause you to use the
> guest_cpu_user_regs() instead. So you still crash, but the crash site is now
> the hypercall call site.

Indeed, that is true. I do think there is some value in avoiding
guest_cpu_user_regs(), but its theoretical at best. Magnus and I will
fold the arguments as you requested.

-- 
Horms
  H: http://www.vergenet.net/~horms/
  W: http://www.valinux.co.jp/en/


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