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

From: David Kiarie
Subject: Re: [Qemu-devel] [V9 0/4] AMD IOMMU
Date: Wed, 4 May 2016 13:51:43 +0300

On Wed, May 4, 2016 at 10:39 AM, Valentine Sinitsyn
<address@hidden> wrote:
> Hi everyone,
> On 04.05.2016 12:05, David Kiarie wrote:
>> On Wed, May 4, 2016 at 9:12 AM, Jan Kiszka <address@hidden> 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.

> Valentine

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