Re: [Xen-devel] [PATCH v7 05/11] IOMMU/MMU: propagate IOMMU Device-TLB flush error up to iommu_iotlb_flush{, _all} (top level ones)

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.06.16 at 14:08, <julien.grall@xxxxxxx> wrote:

> 
> On 09/06/16 13:03, Julien Grall wrote:
>> On 09/06/16 12:45, Jan Beulich wrote:
>>>>>> On 09.06.16 at 13:12, <julien.grall@xxxxxxx> wrote:
>>>> On 08/06/16 09:58, Xu, Quan wrote:
>>>>> From: Quan Xu <quan.xu@xxxxxxxxx>
>>>>>
>>>>> Signed-off-by: Quan Xu <quan.xu@xxxxxxxxx>
>>>>> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
>>>>>
>>>>> CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>>>>> CC: Julien Grall <julien.grall@xxxxxxx>
>>>>> CC: Jan Beulich <jbeulich@xxxxxxxx>
>>>>> CC: Kevin Tian <kevin.tian@xxxxxxxxx>
>>>>> ---
>>>>>    xen/arch/arm/p2m.c                  |  4 +++-
>>>>>    xen/common/memory.c                 | 12 ++++++++++--
>>>>>    xen/drivers/passthrough/iommu.c     | 13 +++++++++----
>>>>>    xen/drivers/passthrough/x86/iommu.c |  5 +++--
>>>>>    xen/include/xen/iommu.h             |  5 +++--
>>>>>    5 files changed, 28 insertions(+), 11 deletions(-)
>>>>>
>>>>> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
>>>>> index 6a19c57..65d8f1a 100644
>>>>> --- a/xen/arch/arm/p2m.c
>>>>> +++ b/xen/arch/arm/p2m.c
>>>>> @@ -1178,7 +1178,9 @@ out:
>>>>>        if ( flush )
>>>>>        {
>>>>>            flush_tlb_domain(d);
>>>>> -        iommu_iotlb_flush(d, sgfn, egfn - sgfn);
>>>>> +        ret = iommu_iotlb_flush(d, sgfn, egfn - sgfn);
>>>>
>>>> Sorry for coming late in the discussion. What kind of error do you
>>>> expect to return with iommu_tlb_flush?
>>>>
>>>> Today the ARM SMMU will always return 0 if the TLB flush timeout (see
>>>> arm_smmu_tlb_inv_context).
>>>>
>>>> We may want in the future to return an error when it has timeout,
>>>> however only returning an error is not safe at all. The TLB may contain
>>>> entries which are invalid (because we remove the mapping earlier) and a
>>>> device/domain could take advantage of that.
>>>>
>>>> So I am not sure if we should let running the guest when a flush has
>>>> timeout. Any thoughts?
>>>
>>> Well, did you look at the rest of this series, and the other dependent
>>> one? Guests (other than Dom0) get crashed when a flush times out. I
> 
> I missed the bit "other dependent one". Which series are you talking 
> about? The cover letter does not give any dependent series...

"[Patch v11 0/3] VT-d Device-TLB flush issue"

Jan


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