Re: [Xen-devel] [BUG] After upgrade to Xen 4.12.0 iommu=no-igfx

[Jan Beulich <jbeulich@suse.com>]

On 07.08.2019 11:57, Roger Pau Monné  wrote:
> On Wed, Aug 07, 2019 at 09:08:58AM +0200, Jan Beulich wrote:
>> On 06.08.2019 23:48, Roman Shaposhnik wrote:
>>> On Tue, Aug 6, 2019 at 9:18 AM Roger Pau Monné <roger.pau@citrix.com> wrote:
>>>>
>>>> On Fri, Aug 02, 2019 at 10:05:40AM +0200, Roger Pau Monné wrote:
>>>>> On Thu, Aug 01, 2019 at 11:25:04AM -0700, Roman Shaposhnik wrote:
>>>>>> This patch completely fixes the problem for me!
>>>>>>
>>>>>> Thanks Roger! I'd love to see this in Xen 4.13
>>>>>
>>>>> Thanks for testing!
>>>>>
>>>>> It's still not clear to me why the previous approach didn't work, but
>>>>> I think this patch is better because it removes the usage of
>>>>> {set/clear}_identity_p2m_entry from PV domains. I will submit this
>>>>> formally now.
>>>>
>>>> Sorry to bother again, but since we still don't understand why the
>>>> previous fix didn't work for you, and I can't reproduce this with my
>>>> hardware, could you give the attached patch a try?
>>>
>>> No worries -- and thanks for helping to get it over the finish line --
>>> this is much appreciated!
>>>
>>> I'm happy to say that this latest patch is also working just fine. So
>>> I guess this is the one that's going to land in Xen 4.13?
>>
>> Not necessarily - the other patch is also a candidate, but its
>> description would need to explain what was actually wrong.
>>
>>>> AFAICT the only difference between the non-working version and the
>>>> working version is the flush, so I've added it here.
>>
>> Now I'm afraid I still can't draw a helpful conclusion from Roman's
>> successful test: intel_iommu_hwdom_init(), after having called
>> setup_hwdom_rmrr(), calls iommu_flush_all() (with one other,
>> seemingly innocent call in between). The only conclusion I _could_
>> draw is that iommu_flush_all() doesn't do what its name says. Which
>> would be quite bad. But
>>
>> [orig]
>> iommu_flush_all()
>> -> iommu_flush_iotlb_global(flush_non_present_entry=0)
>> -> flush->iotlb(DMA_TLB_GLOBAL_FLUSH, flush_non_present_entry=0)
>>
>> [patch]
>> iommu_flush_iotlb_all()
>> -> iommu_flush_iotlb(dma_old_pte_present=0, page_count=0)
>> -> iommu_flush_iotlb_dsi(flush_non_present_entry=0)
>> -> flush->iotlb(DMA_TLB_DSI_FLUSH, flush_non_present_entry=0)
>>
>> suggests to me that (as one would infer from the names) is the
>> more through flush. I must be overlooking something ...
> 
> I went over the iotlb queued invalidation code and it seems fine to
> me, I haven't been able to spot any issues with it, and as you say
> above the only difference is the flush type (DSI vs GLOBAL).
> 
> Again and just to make sure it's actually the flush type (and nothing
> in between) the factor that makes this work or break, can you try the
> above patch?

And I take it the "you" here was meant for Roman (only on Cc),
not me.

Jan

> Thanks, Roger.
> ---8<---
> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> index fef97c82f6..3605614aaf 100644
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -1341,7 +1341,7 @@ int set_identity_p2m_entry(struct domain *d, unsigned long gfn_l,
>   
>       if ( !paging_mode_translate(p2m->domain) )
>       {
> -        if ( !need_iommu_pt_sync(d) )
> +        if ( !has_iommu_pt(d) )
>               return 0;
>           return iommu_legacy_map(d, _dfn(gfn_l), _mfn(gfn_l), PAGE_ORDER_4K,
>                                   IOMMUF_readable | IOMMUF_writable);
> @@ -1432,7 +1432,7 @@ int clear_identity_p2m_entry(struct domain *d, unsigned long gfn_l)
>   
>       if ( !paging_mode_translate(d) )
>       {
> -        if ( !need_iommu_pt_sync(d) )
> +        if ( !has_iommu_pt(d) )
>               return 0;
>           return iommu_legacy_unmap(d, _dfn(gfn_l), PAGE_ORDER_4K);
>       }
> diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c
> index 5d72270c5b..885185ad09 100644
> --- a/xen/drivers/passthrough/vtd/iommu.c
> +++ b/xen/drivers/passthrough/vtd/iommu.c
> @@ -2026,7 +2026,7 @@ static int rmrr_identity_mapping(struct domain *d, bool_t map,
>       mrmrr->count = 1;
>       list_add_tail(&mrmrr->list, &hd->arch.mapped_rmrrs);
>   
> -    return 0;
> +    return iommu_flush_all();
>   }
>   
>   static int intel_iommu_add_device(u8 devfn, struct pci_dev *pdev)
> 
> 


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