On 24/06/14 11:23, Will Deacon wrote: > On Wed, May 07, 2014 at 03:55:57PM +0100, Christoffer Dall wrote: >> On Wed, May 07, 2014 at 10:00:21AM +0100, Marc Zyngier wrote: >>> On Tue, May 06 2014 at 7:04:48 pm BST, Christoffer Dall <christoffer.dall@xxxxxxxxxx> wrote: >>>> On Tue, Mar 25, 2014 at 05:08:14PM -0500, Kim Phillips wrote: >>>>> Use the correct memory type for device MMIO mappings: PAGE_S2_DEVICE. >>>>> >>>>> Signed-off-by: Kim Phillips <kim.phillips@xxxxxxxxxx> >>>>> --- >>>>> arch/arm/kvm/mmu.c | 11 ++++++++--- >>>>> 1 file changed, 8 insertions(+), 3 deletions(-) > > [...] > >>>> I think this looks reasonable. >>>> >>>> Acked-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx> >>> >>> I feel like I'm missing some context here, and the commit message is way >>> too terse for me to make sense of it. >>> >>> So far, we can only get into user_mem_abort on a Stage-2 fault >>> (translation or permission) for memory. How can we suddenly get here for >>> a *device* fault? Do we get a special kind of memslot? >>> >>> I'm not saying the patch does anything wrong, but I'd like to understand >>> the rationale behind it. On its own, it doesn't make much sense. >>> >> Think device passthrough. There's nothing preventing user space from >> setting up a memory region to point to device memory (through VFIO or >> /dev/mem). If that's done, we should enforce device memory properties >> so writes don't linger around in the cache to be written some time later >> when that device memory potentially doesn't belong to the VM anymore. >> >> This is just one tiny piece of all of them to make device passthrough >> work, and we could hold off with this patch until we have something more >> complete. On the other hand, we need to start somewhere, and this is >> hardly intrusive and is functionally correct even though you don't have >> a full device passthrough setup. > > Please can you queue this patch up? I need it for my VFIO work, where I'm > registering the PCI BARs using KVM_SET_USER_MEMORY_REGION. > > Without this, I'd have to trap all accesses and do pread/pwrite from > kvmtool instead of mmaping the regions straight through. I'm afraid there as been quite a bit of churn in this department, and the patch doesn't apply any more. Kim, any chance you could respin this patch on top of mainline? Thanks, M. -- Jazz is not dead. It just smells funny... -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
