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

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On 23.11.12 at 11:37, Daniel Kiper [off-list ref] wrote:

On Fri, Nov 23, 2012 at 09:53:37AM +0000, Jan Beulich wrote:

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On 23.11.12 at 02:56, Andrew Cooper [off-list ref] wrote:

On 23/11/2012 01:38, H. Peter Anvin wrote:

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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.

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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