On 2019-12-09 2:00 p.m., Dan Williams wrote: >>>> 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. >> >> I do agree that restriction is not the best fit. But I consider prot >> argument to complicate the API to all users even though it is not really >> clear whether we are going to have many users really benefiting from it. >> Look at the vmalloc API and try to find how many users of __vmalloc do >> not use PAGE_KERNEL. > > At least for this I can foresee at least one more user in the > pipeline, encrypted memory support for persistent memory mappings that > will store the key-id in the ptes. > >> >> So I can see two options. One of them is to add arch_add_memory_prot >> that would allow to have give and extra prot argument or simply call >> an arch independent API to change the protection after arch_add_memory. >> The later sounds like much less code. The memory shouldn't be in use by >> anybody at that stage yet AFAIU. Maybe there even is an API like that. > > I'm ok with passing it the same way as altmap or a new > arch_add_memory_prot() my only hangup with after the fact changes is > the wasted effort it inflicts in the init path for potentially large > address ranges. Yes, I'll change the way it's passed in for v2 as that seems to be generally agreed upon. I can also add a patch to make the name change. And, yes, given our testing, the wasted effort is quite significant so I'm against changing the prots after the fact. Logan
