Re: [Xen-devel] [PATCH v2 01/11] kexec: introduce kexec_ops struct

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.11.12 at 11:37, Daniel Kiper <daniel.kiper@xxxxxxxxxx> 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@xxxxxxxxxx> 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.

Jan


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