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Message-ID: <52CCEE80.20001@linux.intel.com>
Date: Wed, 08 Jan 2014 14:21:52 +0800
From: Jiang Liu <jiang.liu@...ux.intel.com>
To: Kai Huang <dev.kai.huang@...il.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 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.
>
> -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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