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    SubjectRe: [PATCH v2 01/11] kexec: introduce kexec_ops struct
    On Fri, Nov 23, 2012 at 10:51:55AM +0000, Jan Beulich wrote:
    > >>> On 23.11.12 at 11:37, Daniel Kiper <daniel.kiper@oracle.com> wrote:
    > > On Fri, Nov 23, 2012 at 09:53:37AM +0000, Jan Beulich wrote:
    > >> >>> On 23.11.12 at 02:56, Andrew Cooper <andrew.cooper3@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.
    >
    > Even if so, there's no fundamental reason why that kernel image
    > can't be put into Xen controlled space instead.

    Yep, but we must change Xen kexec interface and/or its behavior first.
    If we take that option then we could also move almost all needed things
    from dom0 kernel to Xen. This way we could simplify Linux Kernel
    kexec/kdump infrastructure needed to run on Xen.

    Daniel


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