From: Jason Wang <jasowang@redhat.com>
To: Peter Xu <peterx@redhat.com>
Cc: "Peter Maydell" <peter.maydell@linaro.org>,
"Yan Zhao" <yan.y.zhao@intel.com>,
"Juan Quintela" <quintela@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
qemu-devel@nongnu.org, "Eugenio Pérez" <eperezma@redhat.com>,
"Eric Auger" <eric.auger@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>
Subject: Re: [RFC v2 1/1] memory: Delete assertion in memory_region_unregister_iommu_notifier
Date: Tue, 30 Jun 2020 16:29:19 +0800 [thread overview]
Message-ID: <1b4eaaaf-c2ab-0da8-afb4-1b7b4221e6cf@redhat.com> (raw)
In-Reply-To: <2589d0e9-cc5b-a4df-8790-189b49f1a40e@redhat.com>
On 2020/6/30 上午10:41, Jason Wang wrote:
>
> On 2020/6/29 下午9:34, Peter Xu wrote:
>> On Mon, Jun 29, 2020 at 01:51:47PM +0800, Jason Wang wrote:
>>> On 2020/6/28 下午10:47, Peter Xu wrote:
>>>> On Sun, Jun 28, 2020 at 03:03:41PM +0800, Jason Wang wrote:
>>>>> On 2020/6/27 上午5:29, Peter Xu wrote:
>>>>>> Hi, Eugenio,
>>>>>>
>>>>>> (CCing Eric, Yan and Michael too)
>>>>>>
>>>>>> On Fri, Jun 26, 2020 at 08:41:22AM +0200, Eugenio Pérez wrote:
>>>>>>> diff --git a/memory.c b/memory.c
>>>>>>> index 2f15a4b250..7f789710d2 100644
>>>>>>> --- a/memory.c
>>>>>>> +++ b/memory.c
>>>>>>> @@ -1915,8 +1915,6 @@ void
>>>>>>> memory_region_notify_one(IOMMUNotifier *notifier,
>>>>>>> return;
>>>>>>> }
>>>>>>> - assert(entry->iova >= notifier->start && entry_end <=
>>>>>>> notifier->end);
>>>>>> I can understand removing the assertion should solve the issue,
>>>>>> however imho
>>>>>> the major issue is not about this single assertion but the whole
>>>>>> addr_mask
>>>>>> issue behind with virtio...
>>>>> I don't get here, it looks to the the range was from guest IOMMU
>>>>> drivers.
>>>> Yes. Note that I didn't mean that it's a problem in virtio, it's
>>>> just the fact
>>>> that virtio is the only one I know that would like to support
>>>> arbitrary address
>>>> range for the translated region. I don't know about tcg, but vfio
>>>> should still
>>>> need some kind of page alignment in both the address and the
>>>> addr_mask. We
>>>> have that assumption too across the memory core when we do
>>>> translations.
>>>
>>> Right but it looks to me the issue is not the alignment.
>>>
>>>
>>>> A further cause of the issue is the MSI region when vIOMMU enabled
>>>> - currently
>>>> we implemented the interrupt region using another memory region so
>>>> it split the
>>>> whole DMA region into two parts. That's really a clean approach to IR
>>>> implementation, however that's also a burden to the invalidation
>>>> part because
>>>> then we'll need to handle things like this when the listened range
>>>> is not page
>>>> alighed at all (neither 0-0xfedffff, nor 0xfef0000-MAX). If
>>>> without the IR
>>>> region (so the whole iommu address range will be a single FlatRange),
>>>
>>> Is this a bug? I remember that at least for vtd, it won't do any
>>> DMAR on the
>>> intrrupt address range
>> I don't think it's a bug, at least it's working as how I
>> understand... that
>> interrupt range is using an IR region, that's why I said the IR
>> region splits
>> the DMAR region into two pieces, so we have two FlatRange for the same
>> IOMMUMemoryRegion.
>
>
> I don't check the qemu code but if "a single FlatRange" means
> 0xFEEx_xxxx is subject to DMA remapping, OS need to setup passthrough
> mapping for that range in order to get MSI to work. This is not what
> vtd spec said:
>
> """
>
> 3.14 Handling Requests to Interrupt Address Range
>
> Requests without PASID to address range 0xFEEx_xxxx are treated as
> potential interrupt requests and are not subjected to DMA remapping
> (even if translation structures specify a mapping for this
> range). Instead, remapping hardware can be enabled to subject such
> interrupt requests to interrupt remapping.
>
> """
>
> My understanding is vtd won't do any DMA translation on 0xFEEx_xxxx
> even if IR is not enabled.
Ok, we had a dedicated mr for interrupt:
memory_region_add_subregion_overlap(MEMORY_REGION(&vtd_dev_as->iommu),
VTD_INTERRUPT_ADDR_FIRST,
&vtd_dev_as->iommu_ir, 1);
So it should be fine. I guess the reason that I'm asking is that I
thought "IR" means "Interrupt remapping" but in fact it means "Interrupt
Region"?
But I'm still not clear about the invalidation part for interrupt
region, maybe you can elaborate a little more on this.
Btw, I think guest can trigger the assert in vtd_do_iommu_translate() if
we teach vhost to DMA to that region:
/*
* We have standalone memory region for interrupt addresses, we
* should never receive translation requests in this region.
*/
assert(!vtd_is_interrupt_addr(addr));
Is this better to return false here? (We can work on the fix for vhost
but it should be not trivial)
Thanks
next prev parent reply other threads:[~2020-06-30 8:30 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-26 6:41 [RFC v2 0/1] memory: Delete assertion in memory_region_unregister_iommu_notifier Eugenio Pérez
2020-06-26 6:41 ` [RFC v2 1/1] " Eugenio Pérez
2020-06-26 21:29 ` Peter Xu
2020-06-27 7:26 ` Yan Zhao
2020-06-27 12:57 ` Peter Xu
2020-06-28 1:36 ` Yan Zhao
2020-06-28 7:03 ` Jason Wang
2020-06-28 14:47 ` Peter Xu
2020-06-29 5:51 ` Jason Wang
2020-06-29 13:34 ` Peter Xu
2020-06-30 2:41 ` Jason Wang
2020-06-30 8:29 ` Jason Wang [this message]
2020-06-30 9:21 ` Michael S. Tsirkin
2020-06-30 9:23 ` Jason Wang
2020-06-30 15:20 ` Peter Xu
2020-07-01 8:11 ` Jason Wang
2020-07-01 12:16 ` Peter Xu
2020-07-01 12:30 ` Jason Wang
2020-07-01 12:41 ` Peter Xu
2020-07-02 3:00 ` Jason Wang
2020-06-30 15:39 ` Peter Xu
2020-07-01 8:09 ` Jason Wang
2020-07-02 3:01 ` Jason Wang
2020-07-02 15:45 ` Peter Xu
2020-07-03 7:24 ` Jason Wang
2020-07-03 13:03 ` Peter Xu
2020-07-07 8:03 ` Jason Wang
2020-07-07 19:54 ` Peter Xu
2020-07-08 5:42 ` Jason Wang
2020-07-08 14:16 ` Peter Xu
2020-07-09 5:58 ` Jason Wang
2020-07-09 14:10 ` Peter Xu
2020-07-10 6:34 ` Jason Wang
2020-07-10 13:30 ` Peter Xu
2020-07-13 4:04 ` Jason Wang
2020-07-16 1:00 ` Peter Xu
2020-07-16 2:54 ` Jason Wang
2020-07-17 14:18 ` Peter Xu
2020-07-20 4:02 ` Jason Wang
2020-07-20 13:03 ` Peter Xu
2020-07-21 6:20 ` Jason Wang
2020-07-21 15:10 ` Peter Xu
2020-08-03 16:00 ` Eugenio Pérez
2020-08-04 20:30 ` Peter Xu
2020-08-05 5:45 ` Jason Wang
2020-08-11 17:01 ` Eugenio Perez Martin
2020-08-11 17:10 ` Eugenio Perez Martin
2020-06-29 15:05 ` [RFC v2 0/1] " Paolo Bonzini
2020-07-03 7:39 ` Eugenio Perez Martin
2020-07-03 10:10 ` Paolo Bonzini
2020-08-11 17:55 ` [RFC v3 " Eugenio Pérez
2020-08-11 17:55 ` [RFC v3 1/1] memory: Skip bad range assertion if notifier supports arbitrary masks Eugenio Pérez
2020-08-12 2:24 ` Jason Wang
2020-08-12 8:49 ` Eugenio Perez Martin
2020-08-18 14:24 ` Eugenio Perez Martin
2020-08-19 7:15 ` Jason Wang
2020-08-19 8:22 ` Eugenio Perez Martin
2020-08-19 9:36 ` Jason Wang
2020-08-19 15:50 ` Peter Xu
2020-08-20 2:28 ` Jason Wang
2020-08-21 14:12 ` Peter Xu
2020-09-01 3:05 ` Jason Wang
2020-09-01 19:35 ` Peter Xu
2020-09-02 5:13 ` Jason Wang
2020-08-11 18:10 ` [RFC v3 0/1] memory: Delete assertion in memory_region_unregister_iommu_notifier Eugenio Perez Martin
2020-08-11 19:27 ` Peter Xu
2020-08-12 14:33 ` Eugenio Perez Martin
2020-08-12 21:12 ` Peter Xu
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