Messages in this thread | | | Date | Tue, 5 Feb 2013 13:13:06 -0500 (EST) | From | Nicolas Pitre <> | Subject | Re: [PATCH v5 3/3] ARM: mm: use static_vm for managing static mapped areas |
| |
On Tue, 5 Feb 2013, Rob Herring wrote:
> On 02/04/2013 10:44 PM, Nicolas Pitre wrote: > > On Tue, 5 Feb 2013, Joonsoo Kim wrote: > > > >> A static mapped area is ARM-specific, so it is better not to use > >> generic vmalloc data structure, that is, vmlist and vmlist_lock > >> for managing static mapped area. And it causes some needless overhead and > >> reducing this overhead is better idea. > >> > >> Now, we have newly introduced static_vm infrastructure. > >> With it, we don't need to iterate all mapped areas. Instead, we just > >> iterate static mapped areas. It helps to reduce an overhead of finding > >> matched area. And architecture dependency on vmalloc layer is removed, > >> so it will help to maintainability for vmalloc layer. > >> > >> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> > > [snip] > > >> @@ -859,17 +864,12 @@ static void __init pci_reserve_io(void) > >> { > >> struct vm_struct *vm; > >> unsigned long addr; > >> + struct static_vm *svm; > >> > >> - /* we're still single threaded hence no lock needed here */ > >> - for (vm = vmlist; vm; vm = vm->next) { > >> - if (!(vm->flags & VM_ARM_STATIC_MAPPING)) > >> - continue; > >> - addr = (unsigned long)vm->addr; > >> - addr &= ~(SZ_2M - 1); > >> - if (addr == PCI_IO_VIRT_BASE) > >> - return; > >> + svm = find_static_vm_vaddr((void *)PCI_IO_VIRT_BASE); > >> + if (svm) > >> + return; > >> > >> - } > >> > >> vm_reserve_area_early(PCI_IO_VIRT_BASE, SZ_2M, pci_reserve_io); > >> } > > > > The replacement code is not equivalent. I can't recall why the original > > is as it is, but it doesn't look right to me. The 2MB round down > > certainly looks suspicious. > > The PCI mapping is at a fixed, aligned 2MB mapping. If we find any > virtual address within that region already mapped, it is an error.
Ah, OK. This wasn't clear looking at the code.
> We probably should have had a WARN here.
Indeed.
> > > > The replacement code should be better. However I'd like you to get an > > ACK from Rob Herring as well for this patch. > > It doesn't appear to me the above case is handled. The virt addr is > checked whether it is within an existing mapping, but not whether the > new mapping would overlap an existing mapping. It would be good to check > for this generically rather than specifically for the PCI i/o mapping.
Agreed. However that is checked already in vm_area_add_early(). Therefore the overlap test here is redundant.
Nicolas
| |