Re: [RFC Patch Part2 V1 14/14] iommu/vt-d: update IOMMU state whenmemory hotplug happens

[Kai Huang]

On Tue, Jan 7, 2014 at 5:00 PM, Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx> wrote:
> If static identity domain is created, IOMMU driver needs to update
> si_domain page table when memory hotplug event happens. Otherwise
> PCI device DMA operations can't access the hot-added memory regions.
>
> Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx>
> ---
>  drivers/iommu/intel-iommu.c |   52 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 51 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 83e3ed4..35a987d 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -33,6 +33,7 @@
>  #include <linux/dmar.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/mempool.h>
> +#include <linux/memory.h>
>  #include <linux/timer.h>
>  #include <linux/iova.h>
>  #include <linux/iommu.h>
> @@ -3689,6 +3690,54 @@ static struct notifier_block device_nb = {
>         .notifier_call = device_notifier,
>  };
>
> +static int intel_iommu_memory_notifier(struct notifier_block *nb,
> +                                      unsigned long val, void *v)
> +{
> +       struct memory_notify *mhp = v;
> +       unsigned long long start, end;
> +       struct iova *iova;
> +
> +       switch (val) {
> +       case MEM_GOING_ONLINE:
> +               start = mhp->start_pfn << PAGE_SHIFT;
> +               end = ((mhp->start_pfn + mhp->nr_pages) << PAGE_SHIFT) - 1;
> +               if (iommu_domain_identity_map(si_domain, start, end)) {
> +                       pr_warn("dmar: failed to build identity map for [%llx-%llx]\n",
> +                               start, end);
> +                       return NOTIFY_BAD;
> +               }

Better to use iommu_prepare_identity_map? For si_domain, if
hw_pass_through is used, there's no page table.

> +               break;
> +       case MEM_OFFLINE:
> +       case MEM_CANCEL_ONLINE:
> +               /* TODO: enhance RB-tree and IOVA code to support of splitting iova */
> +               iova = find_iova(&si_domain->iovad, mhp->start_pfn);
> +               if (iova) {
> +                       unsigned long start_pfn, last_pfn;
> +                       struct dmar_drhd_unit *drhd;
> +                       struct intel_iommu *iommu;
> +
> +                       start_pfn = mm_to_dma_pfn(iova->pfn_lo);
> +                       last_pfn = mm_to_dma_pfn(iova->pfn_hi + 1) - 1;
> +                       dma_pte_clear_range(si_domain, start_pfn, last_pfn);
> +                       dma_pte_free_pagetable(si_domain, start_pfn, last_pfn);
> +                       rcu_read_lock();
> +                       for_each_active_iommu(iommu, drhd)
> +                               iommu_flush_iotlb_psi(iommu, si_domain->id,
> +                                       start_pfn, last_pfn - start_pfn + 1, 0);
> +                       rcu_read_unlock();
> +                       __free_iova(&si_domain->iovad, iova);
> +               }

The same as above. Looks we need to consider hw_pass_through for the si_domain.

-Kai

> +               break;
> +       }
> +
> +       return NOTIFY_OK;
> +}
> +
> +static struct notifier_block intel_iommu_memory_nb = {
> +       .notifier_call = intel_iommu_memory_notifier,
> +       .priority = 0
> +};
> +
>  int __init intel_iommu_init(void)
>  {
>         int ret = -ENODEV;
> @@ -3761,8 +3810,9 @@ int __init intel_iommu_init(void)
>         init_iommu_pm_ops();
>
>         bus_set_iommu(&pci_bus_type, &intel_iommu_ops);
> -
>         bus_register_notifier(&pci_bus_type, &device_nb);
> +       if (si_domain)
> +               register_memory_notifier(&intel_iommu_memory_nb);
>
>         intel_iommu_enabled = 1;
>
> --
> 1.7.10.4
>
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