Messages in this thread | | | Date | Sat, 19 Jun 2010 09:43:35 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86: OLPC: add support for calling into OpenFirmware (v5) |
| |
* H. Peter Anvin <hpa@zytor.com> wrote:
> On 06/18/2010 12:56 PM, Ingo Molnar wrote: > > > > * H. Peter Anvin <hpa@zytor.com> wrote: > > > >> On 06/18/2010 12:42 PM, Andres Salomon wrote: > >>> + > >>> + /* install OFW's PDE permanently into the kernel's pgtable */ > >>> + set_pgd(&swapper_pg_dir[OLPC_OFW_PDE_NR], *ofw_pde); > >>> + flush_tlb(); > >>> + early_iounmap(base, sizeof(olpc_ofw_pgd) * PTRS_PER_PGD); > >> > >> I just realized... this flush_tlb() is actually not necessary since on x86 > >> it is always legal to go from a less permissive configuration to a more > >> permissive, and the initial configuration is "not present" which is > >> maximally nonpermissive. > >> > >> Could you take it out and make sure it still works? > > > > small nit: an optimization barrier would still be needed if the result is > > being relied on by the kernel. > > > > In this case the optimization barrier is implicit at the return from an > out of line function.
Which non-obvious side-effect at minimum deserves a comment. (but yes, i'm just nitpicking)
Thanks,
Ingo
| |