On Tue, Aug 7, 2018 at 1:21 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > 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. Agreed.
