On Tue, 2009-10-13 at 11:07 +0900, Paul Mundt wrote: > On Mon, Oct 12, 2009 at 06:03:12PM +0100, Russell King wrote: > > On Mon, Oct 12, 2009 at 05:09:53PM +0100, Hugh Dickins wrote: > > > Sorry to muddy the waters on this, if you and Dave are sure that > > > you have the right fix, down in your architectures, and that fix > > > isn't going to hurt your performance significantly. > > > > If I look at the issue from this point of view: > > > > - we are using PG_arch_1 to delay cache handling for the page > > > > - if PG_arch_1 is set on a page, we set it explicitly because we > > didn't do some flushing between the allocation of the page and > > mapping it into userspace > > > > - if a page with PG_arch_1 set ever gets to userspace, this can > > only be because we did the lazy flushing thing > > > > I don't see that there should have been any bearing on whether a page > > has a mapping or not when we get to update_mmu_cache. The issue here > > is that > if PG_arch_1 is set on a page, then we didn't flush it at > > the time when we believed it was appropriate to do so. < > > > > Tell me I'm wrong (having only just sent it to Linus...) > > Having looked at the ARM fix, in the !mapping case do you not need the > I-cache flush on vma->vm_flags & VM_EXEC? Or is the presumption that > flush_icache_page()-type action doesn't need to be undertaken by > flush_dcache_page()/update_mmu_cache() when there is no page_mapping()? If I understand Nitin's scenario correctly, I think it should also invalidate the I-cache. For executable anonymous pages containing, it's the user app writing the code (JIT etc.) and it calls an ARM-specific syscall for I and D cache maintenance. If such page is read back from swap, following Nitin's scenario, the I-cache would need to be invalidated as well otherwise it can have stale entries. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
