From mboxrd@z Thu Jan 1 00:00:00 1970 From: robherring2@gmail.com (Rob Herring) Date: Tue, 05 Feb 2013 13:12:51 -0600 Subject: [PATCH v5 3/3] ARM: mm: use static_vm for managing static mapped areas In-Reply-To: References: <1360024314-1895-1-git-send-email-iamjoonsoo.kim@lge.com> <1360024314-1895-4-git-send-email-iamjoonsoo.kim@lge.com> <51114134.4070503@gmail.com> Message-ID: <511159B3.8020000@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 02/05/2013 12:13 PM, Nicolas Pitre wrote: > 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 >> >> [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. Ah, right. In that case: Acked-by: Rob Herring Rob