On Fri, Sep 29, 2006 at 01:13:17PM +0800, Zou, Nanhai wrote: > > -----Original Message----- > > From: linux-ia64-owner@xxxxxxxxxxxxxxx > > [mailto:linux-ia64-owner@xxxxxxxxxxxxxxx] On Behalf Of Horms > > Sent: 2006年9月29日 11:03 > > To: Zou, Nanhai > > Cc: Magnus Damm; Tristan Gingold; Linux-IA64; > > xen-ia64-devel@xxxxxxxxxxxxxxxxxxx > > Subject: Re: [Xen-ia64-devel] Re: ia64 kexec: xen -> linux > > > > 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. > > > That is why I suggest you to return error in the set_virtual_address_map() in purgatory code. That will force the second kernel to use EFI physical call. Sure. I think that is a pretty good idea. Except that we need to make sure that set_virtual_address_map() isn't called by the original code (well at least not a real working version), as once it is called real mode EFI calls can no longer be 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
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