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Date: Wed, 8 Jan 2014 14:27:56 +0800
From: Kai Huang <dev.kai.huang@...il.com>
To: Jiang Liu <jiang.liu@...ux.intel.com>
Cc: Joerg Roedel <joro@...tes.org>,
David Woodhouse <dwmw2@...radead.org>,
Yinghai Lu <yinghai@...nel.org>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Dan Williams <dan.j.williams@...el.com>,
Vinod Koul <vinod.koul@...el.com>,
Tony Luck <tony.luck@...el.com>, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org,
iommu@...ts.linux-foundation.org
Subject: Re: [RFC Patch Part2 V1 14/14] iommu/vt-d: update IOMMU state when
memory hotplug happens
On Wed, Jan 8, 2014 at 2:21 PM, Jiang Liu <jiang.liu@...ux.intel.com> wrote:
>
>
> On 2014/1/8 14:14, Kai Huang wrote:
>> On Wed, Jan 8, 2014 at 2:01 PM, Jiang Liu <jiang.liu@...ux.intel.com> wrote:
>>>
>>>
>>> On 2014/1/8 13:07, Kai Huang wrote:
>>>> On Tue, Jan 7, 2014 at 5:00 PM, Jiang Liu <jiang.liu@...ux.intel.com> 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@...ux.intel.com>
>>>>> ---
>>>>> 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.
>>> Hi Kai,
>>> Good catch!
>>> Seems function iommu_prepare_identity_map() is designed to handle
>>> RMRRs. So how about avoiding of registering memory hotplug notifier
>>> if hw_pass_through is true?
>>
>> I think that's also fine :)
>>
>> Btw, I have a related question to memory hotplug but not related to
>> intel IOMMU specifically. For the devices use DMA remapping, suppose
>> the device is already using the memory that we are trying to remove,
>> is this case, looks we need to change the existing iova <-> pa
>> mappings for the pa that is in the memory range about to be removed,
>> and reset the mapping to different pa (iova remains the same). Does
>> existing code have this covered? Is there a generic IOMMU layer memory
>> hotplug notifier to handle memory removal?
> That's a big issue about how to reclaim memory in use. Current rule
> is that memory used by DMA won't be removed until released.
>
Understood. Thanks.
-Kai
>>
>> -Kai
>>>
>>> Thanks!
>>> Gerry
>>>
>>>>
>>>>> + 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
>>>>>
>>>>> _______________________________________________
>>>>> iommu mailing list
>>>>> iommu@...ts.linux-foundation.org
>>>>> https://lists.linuxfoundation.org/mailman/listinfo/iommu
--
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