[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [Patch V2] expand x86 arch_shared_info to support linear p2m list
On 01/12/14 10:15, Jan Beulich wrote: >>>> On 01.12.14 at 10:29, <JGross@xxxxxxxx> wrote: >> The x86 struct arch_shared_info field pfn_to_mfn_frame_list_list >> currently contains the mfn of the top level page frame of the 3 level >> p2m tree, which is used by the Xen tools during saving and restoring >> (and live migration) of pv domains and for crash dump analysis. With >> three levels of the p2m tree it is possible to support up to 512 GB of >> RAM for a 64 bit pv domain. >> >> A 32 bit pv domain can support more, as each memory page can hold 1024 >> instead of 512 entries, leading to a limit of 4 TB. >> >> To be able to support more RAM on x86-64 switch to a virtual mapped >> p2m list. >> >> This patch expands struct arch_shared_info with a new p2m list virtual >> address, the root of the page table root and a p2m generation count. >> The new information is indicated by the domain to be valid by storing >> ~0UL into pfn_to_mfn_frame_list_list. The hypervisor indicates >> usability of this feature by a new flag XENFEAT_virtual_p2m. >> >> Right now XENFEAT_virtual_p2m will not be set. This will change when >> the Xen tools support the virtual mapped p2m list. > > This seems wrong: XENFEAT_* only reflect hypervisor capabilities. > I.e. the availability of the new functionality may need to be > advertised another way - xenstore perhaps? Xenstore doesn't work for dom0. Shouldn't this be something the guest kernel reports using a ELF note bit? When building a domain (either in Xen for dom0 or in the tools), the builder may provide a linear p2m iff supported by the guest kernel and then (and only then) can it provide a guest with > 512 GiB. David _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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