On Fri, Sep 29, 2006 at 10:21:33AM +0800, Zou, Nanhai wrote: > > -----Original Message----- > > From: Magnus Damm [mailto:magnus.damm@xxxxxxxxx] > > Sent: 2006年9月28日 20:34 > > To: Tristan Gingold > > Cc: Horms; Zou, Nanhai; Linux-IA64; xen-ia64-devel@xxxxxxxxxxxxxxxxxxx > > Subject: Re: [Xen-ia64-devel] Re: ia64 kexec: xen -> linux > > > > On 9/28/06, Tristan Gingold <Tristan.Gingold@xxxxxxxx> wrote: > > > Le Jeudi 28 Septembre 2006 03:27, Horms a écrit : > > > > On Wed, Sep 27, 2006 at 11:52:12AM +0200, Tristan Gingold wrote: > > > > > Linux and xen call efi in real mode if set_virtual_address_map fails. > > > > > You may add an option in both xen and linux to force calling efi in real > > > > > mode. This should be really simple and you will be able to make progress. > > > > > > > > Great, I will test this out and see how it goes. > > > > > > > > > The only possible drawback is performance. > > > > > > > > What kind of performance issues would you expect? > > > Making EFI calls in physical mode is slower: Linux must switch from and to > > > virtual mode. > > > > > > However EFI calls are very unfrequent so the impact should be almost nul. > > > > This makes me wonder - is it really worth having two code paths in that case? > > > > / magnus > > I am still not quiet clear about the particular issue on Xen. > > For native IA64, > I put an empty efi.set_virtual_address_map() in purgatory code, So > when the second kernel boots, it will still call to > set_virtual_address_map() as if it successes. I guess you can modify > the empty function in purgatory to return an error. So the second > kernel will call EFI in physical mode. I'm not 100% sure what the issue with xen->linux and linux->xen is either. However my theory is that it relates to the fact that in linux PAGE_OFFSET is 0xe000..., while in Xen it is 0xf000..., and thus any addressing setup using efi.set_virtual_address_map() in one would seem to be invalid in the other. In any case, the problem that I am seeing is that while linux->linux and xen->xen (UP only for now) can be made to work, both xen->linux and linux->xen halt when making an EFI call fairly early on in boot. More specifically, it halts on a call to efi_gettimeofday() which is backed by efi.get_time. Other than the call to efi.set_virtual_address_map() I'm assuming that this is more or less the first efi runtime call that is made. -- Horms H: http://www.vergenet.net/~horms/ W: http://www.valinux.co.jp/en/ - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
|