On Thu, 2015-12-03 at 11:01 -0800, Linus Torvalds wrote: > On Thu, Dec 3, 2015 at 10:40 AM, Borislav Petkov <bp@xxxxxxxxx> wrote: > > On Thu, Dec 03, 2015 at 11:54:19AM -0700, Toshi Kani wrote: > > > Adding a new type for regular memory will require inspecting the > > > codes using IORESOURCE_MEM currently, and modify them to use the new > > > type if their target ranges are regular memory. There are many > > > references to this type across multiple architectures and drivers, > > > which make this inspection and testing challenging. > > > > What's wrong with adding a new type_flags to struct resource and not > > touching IORESOURCE_* at all? > > Bah. Both of these ideas are bogus. > > Just add a new flag. The bits are already modifiers that you can > *combine* to show what kind of resource it is, and we already have > things like IORESOURCE_PREFETCH etc, that are in *addition* to the > normal IORESOURCE_MEM bit. > > Just add another modifier: IORESOURCE_RAM. > > So it would still show up as IORESOURCE_MEM, but it would have > additional information specifying that it's actually RAM. > > If somebody does something like > > if (res->flags == IORESOURCE_MEM) > > then they are already completely broken and won't work *anyway*. It's > a bitmask, bit a set of values. Yes, if we can assign new modifiers, that will be quite simple. :-) I assume we can allocate new bits from the remaining free bits as follows. +#define IORESOURCE_SYSTEM_RAM 0x01000000 /* System RAM */ +#define IORESOURCE_PMEM 0x02000000 /* Persistent memory */ #define IORESOURCE_EXCLUSIVE 0x08000000 /* Userland may not map this resource */ Note, SYSTEM_RAM represents the OS memory, i.e. "System RAM", not any RAM ranges. With the new modifiers, region_intersect() can check these ranges. One caveat is that the modifiers are not very extensible for new types as they are bit maps. region_intersect() will no longer be capable of checking any regions with any given name. I think this is OK since this function was introduced recently, and is only used for checking "System RAM" and "Persistent Memory" (with this patch series). Thanks, -Toshi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>