Messages in this thread | | | Date | Tue, 13 Feb 2007 18:34:28 -0800 | From | Dan Hecht <> | Subject | Re: [patch 05/21] Xen-paravirt: paravirt_ops: allocate a fixmap slot |
| |
On 02/13/2007 05:36 PM, Jeremy Fitzhardinge wrote: > Dan Hecht wrote: >> Why doesn't Xen allocate the shared_info page from the pseudo-physical >> space? Doesn't it already have to steal pages from the >> pseudo-physical space for e.g. initial page tables, console, etc? Why >> not do the same for shared_info, and then you don't need a reserve the >> fixmap slot. > > Unlike the pagetable pages or the console page, the shared info page > doesn't have a pseudo-physical address, so in order to map it we need to > directly construct a pte containing the mfn for that page.
Right. But that is only because Xen decides to allocate the page from the (machine) physical space, rather than from the pseudo-physical space. My question is: why doesn't Xen allocate shared_info from the pseudo-physical space? If it had, then this page wouldn't need to be treated specially. I'm not sure, but I seem to remember on 64-bit Xen/XenLinux allocated shared_info from pseudo-physical space already...
Inserting > this mapping into the fixmap space seems like the easiest way to do > this. It's not like a fixmap slot costs anything. > >
I don't really have an objection to stealing a fixmap slot, just seems cleaner if you didn't have to special case the shared_info.
Dan - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |