On Mon, Sep 23, 2024 at 08:18:57AM +0100, Will Deacon wrote: > On Mon, Sep 23, 2024 at 09:57:14AM +0800, Liao, Chang wrote: > > Unfortunately, the comparison assumes the D-cache and I-cache are already > > in sync for the slot being copied. But this assumption is flawed if we start > > with a page with some random bits and D-cache has not been sychronized with > > I-cache. So, besides __GFP_ZERO, should we have a additional cache flush > > after page allocation? > > No, I think Oleg's right. The initial cache maintenance will happen when the > executable pte is installed.
For some reason I had kprobes in mind, did not realise that this page ends up in user-space. So yes, we have cache maintenance when the pte is set to point to this page. Subsequent changes will need cache maintenance. > However, we should use __GFP_ZERO anyway because I don't think it's a > good idea to map an uninitialised page into userspace. Oh, that's not good. -- Catalin
