On Tue, 7 Aug 2018, Andy Lutomirski wrote: > On Tue, Aug 7, 2018 at 11:34 AM, Dave Hansen <dave.hansen@xxxxxxxxx> wrote: > > On 08/07/2018 03:24 AM, Joerg Roedel wrote: > >> The function sets the global-bit on cloned PMD entries, > >> which only makes sense when the permissions are identical > >> between the user and the kernel page-table. > >> > >> Further, only write-permissions are cleared for entry-text > >> and kernel-text sections, which are not writeable anyway. > > > > I think this patch is correct, but I'd be curious if Andy remembers why > > we chose to clear _PAGE_RW on these things. It might have been that we > > were trying to say that the *entry* code shouldn't write to this stuff, > > regardless of whether the normal kernel can. > > > > But, either way, I agree with the logic here that Global pages must > > share permissions between both mappings, so feel free to add my Ack. I > > just want to make sure Andy doesn't remember some detail I'm forgetting. > > I suspect it's because we used to (and maybe still do) initialize the > user tables before mark_read_only(). We still do that because we need the entry stuff working for interrupts early on. We now repeat the clone after mark_ro so the mask RW is not longer required. Thanks, tglx
