Messages in this thread |  | | | Subject | Re: [RFC][PATCH] vmalloc: simplify vread()/vwrite() | | From | Huang Ying <> | | Date | Thu, 07 Jan 2010 11:15:41 +0800 |
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On Thu, 2010-01-07 at 10:50 +0800, Wu, Fengguang wrote: > On Thu, Jan 07, 2010 at 09:38:25AM +0800, KAMEZAWA Hiroyuki wrote: > > On Thu, 7 Jan 2010 09:24:59 +0800 > > Wu Fengguang <fengguang.wu@intel.com> wrote: > > > > > vread()/vwrite() is only called from kcore/kmem to access one page at > > > a time. So the logic can be vastly simplified. > > > > > I recommend you to rename the function because safety of function is > > changed and you can show what callers are influenced. > > OK. > > > > The changes are: > > > - remove the vmlist walk and rely solely on vmalloc_to_page() > > > - replace the VM_IOREMAP check with (page && page_is_ram(pfn)) > > > > > > The VM_IOREMAP check is introduced in commit d0107eb07320b for per-cpu > > > alloc. Kame, would you double check if this change is OK for that > > > purpose? > > > > > I think VM_IOREMAP is for avoiding access to device configuration area and > > unexpected breakage in device. Then, VM_IOREMAP are should be skipped by > > the caller. (My patch _just_ moves the avoidance of callers to vread()/vwrite()) > > "device configuration area" is not RAM, so testing of RAM would be > able to skip them? > > > > > > The page_is_ram() check is necessary because kmap_atomic() is not > > > designed to work with non-RAM pages. > > > > > I think page_is_ram() is not a complete method...on x86, it just check > > e820's memory range. checking VM_IOREMAP is better, I think. > > (double check) Not complete or not safe? > > EFI seems to not update e820 table by default. Ying, do you know why?
In EFI system, E820 table is constructed from EFI memory map in boot loader, so I think you can rely on E820 table.
Best Regards, Huang Ying
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