On Tue, Feb 07, 2017 at 04:28:04PM +0800, Peter Xu wrote:
> A cleanup for vfio_iommu_map_notify(). Now we will fetch vaddr even if
> the operation is unmap, but it won't hurt much.
>
> One thing to mention is that we need the RCU read lock to protect the
> whole translation and map/unmap procedure.
>
> Acked-by: Alex Williamson <alex.williamson@redhat.com>
> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> Signed-off-by: Peter Xu <peterx@redhat.com>
So, I know I reviewed this already, but looking again I'm confused.
I'm not sure how the original code ever worked: if this is an unmap
(perm == IOMMU_NONE), then I wouldn't even expect
iotlb->translated_addr to have a valid value, but we're passing it to
address_space_translate() and failing if it it doesn't give us
sensible results.
> ---
> hw/vfio/common.c | 65 +++++++++++++++++++++++++++++++++++++++-----------------
> 1 file changed, 45 insertions(+), 20 deletions(-)
>
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 174f351..42c4790 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -294,54 +294,79 @@ static bool vfio_listener_skipped_section(MemoryRegionSection *section)
> section->offset_within_address_space & (1ULL << 63);
> }
>
> -static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
> +/* Called with rcu_read_lock held. */
> +static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb, void **vaddr,
> + bool *read_only)
> {
> - VFIOGuestIOMMU *giommu = container_of(n, VFIOGuestIOMMU, n);
> - VFIOContainer *container = giommu->container;
> - hwaddr iova = iotlb->iova + giommu->iommu_offset;
> MemoryRegion *mr;
> hwaddr xlat;
> hwaddr len = iotlb->addr_mask + 1;
> - void *vaddr;
> - int ret;
> -
> - trace_vfio_iommu_map_notify(iotlb->perm == IOMMU_NONE ? "UNMAP" : "MAP",
> - iova, iova + iotlb->addr_mask);
> -
> - if (iotlb->target_as != &address_space_memory) {
> - error_report("Wrong target AS \"%s\", only system memory is allowed",
> - iotlb->target_as->name ? iotlb->target_as->name : "none");
> - return;
> - }
> + bool writable = iotlb->perm & IOMMU_WO;
>
> /*
> * The IOMMU TLB entry we have just covers translation through
> * this IOMMU to its immediate target. We need to translate
> * it the rest of the way through to memory.
> */
> - rcu_read_lock();
> mr = address_space_translate(&address_space_memory,
> iotlb->translated_addr,
> - &xlat, &len, iotlb->perm & IOMMU_WO);
> + &xlat, &len, writable);
> if (!memory_region_is_ram(mr)) {
> error_report("iommu map to non memory area %"HWADDR_PRIx"",
> xlat);
> - goto out;
> + return false;
> }
> +
> /*
> * Translation truncates length to the IOMMU page size,
> * check that it did not truncate too much.
> */
> if (len & iotlb->addr_mask) {
> error_report("iommu has granularity incompatible with target AS");
> + return false;
> + }
> +
> + *vaddr = memory_region_get_ram_ptr(mr) + xlat;
> + *read_only = !writable || mr->readonly;
> +
> + return true;
> +}
> +
> +static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
> +{
> + VFIOGuestIOMMU *giommu = container_of(n, VFIOGuestIOMMU, n);
> + VFIOContainer *container = giommu->container;
> + hwaddr iova = iotlb->iova + giommu->iommu_offset;
> + bool read_only;
> + void *vaddr;
> + int ret;
> +
> + trace_vfio_iommu_map_notify(iotlb->perm == IOMMU_NONE ? "UNMAP" : "MAP",
> + iova, iova + iotlb->addr_mask);
> +
> + if (iotlb->target_as != &address_space_memory) {
> + error_report("Wrong target AS \"%s\", only system memory is allowed",
> + iotlb->target_as->name ? iotlb->target_as->name : "none");
> + return;
> + }
> +
> + rcu_read_lock();
> +
> + if (!vfio_get_vaddr(iotlb, &vaddr, &read_only)) {
> goto out;
> }
>
> if ((iotlb->perm & IOMMU_RW) != IOMMU_NONE) {
> - vaddr = memory_region_get_ram_ptr(mr) + xlat;
> + /*
> + * vaddr is only valid until rcu_read_unlock(). But after
> + * vfio_dma_map has set up the mapping the pages will be
> + * pinned by the kernel. This makes sure that the RAM backend
> + * of vaddr will always be there, even if the memory object is
> + * destroyed and its backing memory munmap-ed.
> + */
> ret = vfio_dma_map(container, iova,
> iotlb->addr_mask + 1, vaddr,
> - !(iotlb->perm & IOMMU_WO) || mr->readonly);
> + read_only);
> if (ret) {
> error_report("vfio_dma_map(%p, 0x%"HWADDR_PRIx", "
> "0x%"HWADDR_PRIx", %p) = %d (%m)",
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson