On Mon, 16 Dec 2013 12:56:13 +0000 David Vrabel <david.vrabel@xxxxxxxxxx> wrote: > On 14/12/13 08:32, Andrew Morton wrote: > > On Thu, 12 Dec 2013 12:50:47 +0000 David Vrabel <david.vrabel@xxxxxxxxxx> wrote: > > > >>> each time. But that would require difficult tuning of N. > >>> > >>> I suppose we could just do > >>> > >>> if (!in_interrupt()) > >>> cond_resched(); > >>> > >>> in vunmap_pmd_range(), but that's pretty specific to ghes.c and doesn't > >>> permit unmap-inside-spinlock. > >>> > >>> So I can't immediately think of a suitable fix apart from adding a new > >>> unmap_kernel_range_atomic(). Then add a `bool atomic' arg to > >>> vunmap_page_range() and pass that all the way down. > >> > >> That would work for the unmap, but looking at the GHES driver some more > >> and it looks like it's call to ioremap_page_range() is already unsafe -- > >> it may need to allocate a new PTE page with a non-atomic alloc in > >> pte_alloc_one_kernel(). > >> > >> Perhaps what's needed here is a pair of ioremap_page_atomic() and > >> iounmap_page_atomic() calls? With some prep function to sure the PTE > >> pages (etc.) are preallocated. > > > > Is ghes.c the only problem source here? If so then a suitable solution > > would be to declare that driver hopelessly busted and proceed as if it > > didn't exist :( > > All the other callers do so from non-atomic context. ghes.c is the only > broken caller. > > Shall I resend or are you happy to take the patch off the first email in > this thread? Well first we should attempt to wake up the ghes maintainers and tell them we're about to break their stuff. (Which I believe is already broken). The fix won't be easy - presumably ghes will need to punt all its IRQ- and NMI_context operations up into kernel thread context. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
