[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v4 0/9] toolstack-based approach to pvhvm guest kexec
On Wed, Dec 03, 2014 at 06:16:12PM +0100, Vitaly Kuznetsov wrote: > Changes from RFCv3: > This is the first non-RFC series as no major concerns were expressed. I'm > trying > to address Jan's comments. Changes are: > - Move from XEN_DOMCTL_set_recipient to XEN_DOMCTL_devour (I don't really like > the name but nothing more appropriate came to my mind) which incorporates > former XEN_DOMCTL_set_recipient and XEN_DOMCTL_destroydomain to prevent > original domain from changing its allocations during transfer procedure. > - Check in free_domheap_pages() that assign_pages() succeeded. > - Change printk() in free_domheap_pages(). > - DOMDYING_locked state was introduced to support XEN_DOMCTL_devour. > - xc_domain_soft_reset() got simplified a bit. Now we just wait for the > original > domain to die or loose all its pages. > - rebased on top of current master branch. > > Changes from RFC/WIPv2: > > Here is a slightly different approach to memory reassignment. Instead of > introducing new (and very doubtful) XENMEM_transfer operation introduce > simple XEN_DOMCTL_set_recipient operation and do everything in > free_domheap_pages() > handler utilizing normal domain destroy path. This is better because: > - The approach is general-enough > - All memory pages are usually being freed when the domain is destroyed > - No special grants handling required > - Better supportability > > With regards to PV: > Though XEN_DOMCTL_set_recipient works for both PV and HVM this patchset does > not > bring PV kexec/kdump support. xc_domain_soft_reset() is limited to work with > HVM > domains only. The main reason for that is: it is (in theory) possible to save > p2m > and rebuild them with the new domain but that would only allow us to resume > execution > from where we stopped. If we want to execute new kernel we need to build the > same > kernel/initrd/bootstrap_pagetables/... structure we build to boot PV domain > initially. > That however would destroy the original domain's memory thus making kdump > impossible. > To make everything work additional support from kexec userspace/linux kernel > is > required and I'm not sure it makes sense to implement all this stuff in the > light of > PVH. > What would happen if you soft reset a PV guest? At the very least soft reset should be explicitly forbidden in PV case. > Original description: > > When a PVHVM linux guest performs kexec there are lots of things which > require taking care of: > - shared info, vcpu_info > - grants > - event channels > - ... Is there a complete list? > Instead of taking care of all these things we can rebuild the domain > performing kexec from scratch doing so-called soft-reboot. > > The idea was suggested by David Vrabel, Jan Beulich, and Konrad Rzeszutek > Wilk. > As this approach requires toolstack do complex interaction with hypervisor and preserve / throw away a bunch of states. I think the whole procedure should be documented. It would also be helpful if you link to previous discussions in your cover letter. Wei. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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