[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [Draft A] Boot ABI for HVM guests without a device-model
On Thu, Jun 11, 2015 at 08:18:27AM +0100, Jan Beulich wrote: > >>> On 10.06.15 at 20:55, <konrad.wilk@xxxxxxxxxx> wrote: > > On Wed, Jun 10, 2015 at 02:34:00PM +0200, Roger Pau Monné wrote: > >> The first three notes contain information about the guest kernel and > >> the Xen hypercall ABI version. The following notes are of special > >> interest: > >> > >> * XEN_ELFNOTE_PADDR_OFFSET: the offset of the ELF paddr field from the > >> actual required physical address. > >> * XEN_ELFNOTE_PADDR_ENTRY: the 32bit entry point into the kernel. > > > > Is 'P' suppose to be 'physical' ? > > > > I am not sure how this will work with an ELF 64-bit binary like > > the Linux kernel. Usually we use the virtual address but with > > us starting in 32-bit mode with an 64-bit virtual address won't work. > > So first you correctly decode the 'P' as physical, and then you're > concerned about _virtual_ addresses? The Linux ELF PHDR has > perfectly valid virtual _and_ physical addresses in it afaict. > > >> Note that the boot protocol resembles the multiboot1 specification, > >> this is done so OSes with multiboot1 entry points can reuse those if > >> desired. Also note that the processor starts with paging disabled, > >> which means that all the memory addresses in the start_info page will > >> be physical memory addresses. > > > > Wow?! Pagetables disabled?! Why? Usually boot loaders start with some > > pagetables setup for the OS - to cover at least the kernel and the > > ramdisk. Either it being in 1-1 pagetables or such. > > Mind pointing out which boot loaders you think about here? Both > multiboot variants surely start the OS in non-paged protected > mode. Of course, UEFI is completely different (because it wants > itself to run in 64-bit mode). I was thinking of UEFI. Other ones as you pointed out are more primitive. > > Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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