On Fri, 5 Oct 2007 12:36:33 +0100 (BST) Hugh Dickins <[EMAIL PROTECTED]> wrote:
> To my naive mind, your problem actually lies in those two stages: > whatever marks the pages RO should not be keeping Xen in ignorance. It does. Telling Xen to pin the page as a page table page is basically the first thing a Xen kernel does after marking the page read-only. This makes for a narrow race window, during which ptep_test_and_clear_young cannot clear the referenced bit and may end up causing a crash. We do not care about it not clearing the referenced bit during that window, since it will be cleared during the next go-around and the race is very rare. Hence, the only thing we need to fix is the crash. We can do that by adding an entry for ptep_test_and_clear_young to the exception table. This way we do not need to turn this into a new paravirt ops hook (since the fast path is exactly the same as x86 native) and there is no need for added complexity. Also, Xen would not conflict with SPLIT_PTLOCK_CPUS. -- All Rights Reversed - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
