On Fri, Nov 23, 2012 at 09:53:37AM +0000, Jan Beulich wrote: > >>> On 23.11.12 at 02:56, Andrew Cooper <andrew.cooper3 at citrix.com> wrote: > > On 23/11/2012 01:38, H. Peter Anvin wrote: > >> I still don't really get why it can't be isolated from dom0, which would > > make more sense to me, even for a Xen crash. > >> > > > > The crash region (as specified by crashkernel= on the Xen command line) > > is isolated from dom0. > > > > dom0 (using the kexec utility etc) has the task of locating the Xen > > crash notes (using the kexec hypercall interface), constructing a binary > > blob containing kernel, initram and gubbins, and asking Xen to put this > > blob in the crash region (again, using the kexec hypercall interface). > > > > I do not see how this is very much different from the native case > > currently (although please correct me if I am misinformed). Linux has > > extra work to do by populating /proc/iomem with the Xen crash regions > > boot (so the kexec utility can reference their physical addresses when > > constructing the blob), and should just act as a conduit between the > > kexec system call and the kexec hypercall to load the blob. > > But all of this _could_ be done completely independent of the > Dom0 kernel's kexec infrastructure (i.e. fully from user space, > invoking the necessary hypercalls through the privcmd driver). No, this is impossible. kexec/kdump image lives in dom0 kernel memory until execution. That is why privcmd driver itself is not a solution in this case. > It's just that parts of the kexec infrastructure can be re-used > (and hence that mechanism probably seemed the easier approach > to the implementer of the original kexec-on-Xen). If the kernel > folks dislike that re-use (quite understandably looking at how > much of it needs to be re-done), that shouldn't prevent us from > looking into the existing alternatives. This is last resort option. First I think we should try to find good solution which reuses existing code as much as possible. Daniel
