Re: [Xen-devel] [PATCH 3 of 3] KEXEC: Allocate crash structures in low memory

["Jan Beulich" <jbeulich@xxxxxxxx>]

>>> Andrew Cooper <andrew.cooper3@xxxxxxxxxx> 12/31/11 1:12 AM >>>
>The register contents of the pcpus which were running will be available
>in the PR_STATUS notes which are also deliberately allocated in low
>memory by this patch.  To the best of my understanding; to get to the
>dom0 vcpu state, the crashkernel needs access to the domain structs and
>vcpu structs (which I believe are actually allocated below 4GiB) and the

The vCPU ones are, while the domain one isn't.

>Xen page tables which dom0 uses (which inspecting CR3 from the crash
>notes is certainly not in lower memory).  I suspect that there is also
>more which needs to be allocated in lower memory to get a full register
>dump, stack dump, stack trace etc.
>
>The plan is to also have the "all" option from the command line which
>will also allocate the page tables (and other structures where relevant)
>in lower memory, but this is rather more of an overhead than just the
>console ring and crash notes, which will have a more visible impact to
>customers running 32bit PV guests.  This is the reason for separating
>the two via a command line argument.

I'm wondering whether, with much less impact on existing code, and as
already pointed out, restricting the allocation range of
alloc_xenheap_pages() (by way of a command line option) wouldn't get
you what you want.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel