decui_microsoft.com added inline comments. INLINE COMMENTS
> kib wrote in copy.c:79-84 > Note that at the loader/earliest kernel boot phase, we must consider two > different types of addresses, physical and virtual. Kernel is linked at > specific virtual address, and for the text segment of the kernel, it does not > matter a bit which physical addresses back the virtual mappings, as far as > the virtual mapping satisfies the expectation of linker. In principle, the > physical pages do not need to be contiguous even. > > The physical backing is, of course, important too, but it affects different > things. In particular, vm_page_array[] pages must be correctly removed from > the runs, for the physical addresses that are used to map kernel. Another > place which should be adapted is the creation of the initial kernel page > tables, in create_pagetables() pmap function. The function makes explicit > assumption that the kernel is mapped by contig physical pages. > > Another question is how the kernel comprehends the used physical pages to map > it. Kernel could try to inspect the initial (loader) page table it is > started with, but it needs some way to access memory by a physical addresses > for that. Or loader might pass some additional table to inform kernel about > initial mapping, to avoid the need to inspect the page table. IIRC, the UEFI firmware enables protected mode with identity-mapped paging (i.e. VA==PA) , before the execution is transferred to FreeBSD's EFI loader. So here IMO I can treat VA==PA in the patch (it looks FreeBSD UEFI loader doesn't change the VA/PA mapping(?)). I have to admit the fact that I don't know the loader very well and actually it's my first time to have the chance to read some of the code and try to make a patch for it. :-) Please kindly elaborate a little more about the issues that you think exist in the patch and I am happy to dig more into them. REVISION DETAIL https://reviews.freebsd.org/D9686 EMAIL PREFERENCES https://reviews.freebsd.org/settings/panel/emailpreferences/ To: decui_microsoft.com, imp, jhb, will, kib, delphij, emaste, sepherosa_gmail.com, honzhan_microsoft.com, howard0su_gmail.com, marcel Cc: freebsd-virtualization-list _______________________________________________ [email protected] mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-virtualization To unsubscribe, send any mail to "[email protected]"
