Re: [Qemu-devel] [V9 0/4] AMD IOMMU

[Valentine Sinitsyn <valentine.sinitsyn@gmail.com>]

On 04.05.2016 15:51, David Kiarie wrote:
> On Wed, May 4, 2016 at 10:39 AM, Valentine Sinitsyn
> <valentine.sinitsyn@gmail.com> wrote:
>> Hi everyone,
>>
>> On 04.05.2016 12:05, David Kiarie wrote:
>>>
>>> On Wed, May 4, 2016 at 9:12 AM, Jan Kiszka <jan.kiszka@web.de> wrote:
>>>>
>>>> On 2016-04-30 00:42, David Kiarie wrote:
>>>>>
>>>>> These series adds AMD IOMMU support to Qemu. It's currently in the 9th
>>>>> version.
>>>>>
>>>>> In this series I have (hopefully) addressed all the comments made in the
>>>>> previous version.
>>>>> I have also tested and successfully passed-through PCI device 'ac97'
>>>>> with more devices to be tested.
>>>>>
>>>>
>>>> I've done some basic testing with a Jailhouse setup and found it
>>>> working. The ACPI table is now properly parsed and the DMA remapping was
>>>> not disturbing the system after Jailhouse was activated.
>>>>
>>>> However, it was also still not intervening after I started to corrupt
>>>> the configuration, removed DMA target properties from most of the RAM or
>>>> dropped PCI devices.
>>
>> Please also remember that unlisted devices go without translation. To "mute"
>> the device, set V, TV, the DomainId, and zero everything else in the DTE.
>>
>>>
>>> This means you're invalidating DTEs ?
>>>
>>>>
>>>> You are not dropping invalid remapping requests, are you? According to
>>>> the logs, you are detecting them at least:
>>>>
>>>> (amd-iommu)amd_iommu_get_dte: Device Table at 0x3b0d4000
>>>> (amd-iommu)amd_iommu_get_dte: Pte entry at 0x0 is invalid
>>>> (amd-iommu)amd_iommu_translate: devid: 00:02.0 gpa 0x32f39480 hpa
>>>> 0x32f39000
>>>>
>>>> It's a bit hard to test right now if remapping is actually properly
>>>> working in all important cases if you do not reject invalid ones.
>>
>> My understanding is that you should generate an IO_PAGE_FAULT event and drop
>> the request. This doesn't apply to ATS, which is a bit trickier, but we
>> don't address ATS in this patch series anyway, do we?
>
> My next question is what you mean by 'reject' and 'drop'. In I
> encounter an invalid PTE/DTE I don't translate the gpa, it just become
> the hpa which is what is happening above.
What happens if you just ignore the request? I mean, what if you don't 
forward it to anywhere else in QEMU, just log this event and return?

Valentine

>
>>
>> Valentine