On 10.12.19 11:34, Michal Hocko wrote: > On Tue 10-12-19 11:09:46, David Hildenbrand wrote: >> On 10.12.19 11:04, Michal Hocko wrote: >>> On Mon 09-12-19 12:43:40, Dan Williams wrote: >>>> On Mon, Dec 9, 2019 at 12:24 PM Logan Gunthorpe <logang@xxxxxxxxxxxx> wrote: >>>>> >>>>> >>>>> >>>>> On 2019-12-09 12:23 p.m., David Hildenbrand wrote: >>>>>> On 09.12.19 20:13, Logan Gunthorpe wrote: >>> [...] >>>>>>> #ifdef CONFIG_MEMORY_HOTPLUG >>>>>>> -int arch_add_memory(int nid, u64 start, u64 size, >>>>>>> +int arch_add_memory(int nid, u64 start, u64 size, pgprot_t prot, >>>>>>> struct mhp_restrictions *restrictions) >>>>>> >>>>>> Can we fiddle that into "struct mhp_restrictions" instead? >>>>> >>>>> Yes, if that's what people want, it's pretty trivial to do. I chose not >>>>> to do it that way because it doesn't get passed down to add_pages() and >>>>> it's not really a "restriction". If I don't hear any objections, I will >>>>> do that for v2. >>>> >>>> +1 to storing this information alongside the altmap in that structure. >>>> However, I agree struct mhp_restrictions, with the MHP_MEMBLOCK_API >>>> flag now gone, has lost all of its "restrictions". How about dropping >>>> the 'flags' property and renaming the struct to 'struct >>>> mhp_modifiers'? >>> >>> Hmm, this email somehow didn't end up in my inbox so I have missed it >>> before replying. >>> >>> Well, mhp_modifiers makes some sense and it would reduce the API >>> proliferation but how do you expect the prot part to be handled? >>> I really do not want people to think about PAGE_KERNEL or which >>> protection to use because my experience tells that this will get copied >>> without much thinking or simply will break with some odd usecases. >>> So how exactly this would be used? >> >> I was thinking about exactly the same "issue". >> >> 1. default initialization via a function >> >> memhp_modifier_default_init(&modified); >> >> 2. a flag that unlocks the prot field (default:0). Without the flag, it >> is ignored. We can keep the current initialization then. >> >> Other ideas? > > 3. a prot mask to apply on top of PAGE_KERNEL? Or would that be > insufficient/clumsy? > If it works for the given use case, I guess this would be simple and ok. -- Thanks, David / dhildenb
