[Xen-devel] Re: Intel IOMMU: Assigning IGD device: 00:02.1 on some machines, causes Xen to freeze for >2mins because of RMRR mappings

[Tom Rotenberg <tom.rotenberg@xxxxxxxxx>]

Well... i have tested it on Windows XP (win2000 is really nhot that
popular), and it's required for Windows XP, so i don't think that
testing it with a win2000 guest will help, as it's required on XP.

On Tue, Dec 8, 2009 at 4:40 AM, Han, Weidong <weidong.han@xxxxxxxxx> wrote:
> Tom,
>
> As I know, the 00:02.1 is a little bit legacy, it was used in Win2000 to 
> enabled second display functionality. Recent intel platforms doesn't include 
> 00:02.1. Can you have a try with guest win2000?
>
> Regards,
> Weidong
>
> -----Original Message-----
> From: Han, Weidong
> Sent: Thursday, December 03, 2009 10:22 AM
> To: 'Tom Rotenberg'; Keir Fraser
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: Intel IOMMU: Assigning IGD device: 00:02.1 on some machines, 
> causes Xen to freeze for >2mins because of RMRR mappings
>
> I think the issue is not related to preempted hypercall, because 00:02.0 has 
> the same RMRR with 00:02.1, and its pass-through succeeds. One correction, 
> the RMRR (0x7dc00000 to 0x80000000) is not 10,000 pages, is ~1000 pages.
>
> Preempted hypercall implementation is a bit of complex. If you want to have a 
> try, you can refer to existed preempted hypercalls (e.g. 
> XENMEM_increase_reservation).
>
> Regards,
> Weidong
>
>
> -----Original Message-----
> From: Tom Rotenberg [mailto:tom.rotenberg@xxxxxxxxx]
> Sent: Wednesday, December 02, 2009 6:58 PM
> To: Han, Weidong; Keir Fraser
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: Intel IOMMU: Assigning IGD device: 00:02.1 on some machines, 
> causes Xen to freeze for >2mins because of RMRR mappings
>
> And, the other question: how can i make this hypercall preemptive? as
> it may still take too much time for an hypercall (taking into account,
> it needs to map ~10.000 pages...)
>
> On Mon, Nov 30, 2009 at 4:54 PM, Han, Weidong <weidong.han@xxxxxxxxx> wrote:
>> You also need to include below code in the loop:
>>    iommu_flush_cache_entry(pte);
>>    unmap_vtd_domain_page(page);
>>
>> At the end, need to flush iotlb for all pages:
>>        if ( iommu_flush_iotlb_psi(iommu, domain_iommu_domid(d),
>>                                   (paddr_t)gfn << PAGE_SHIFT_4K, pages, 
>>  ----> "pages" means page number
>>                                   !pte_present, flush_dev_iotlb) )
>>            iommu_flush_write_buffer(iommu);
>>
>> Regards,
>> Weidong
>>
>> -----Original Message-----
>> From: Tom Rotenberg [mailto:tom.rotenberg@xxxxxxxxx]
>> Sent: Monday, November 30, 2009 7:17 PM
>> To: Han, Weidong
>> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
>> Subject: Re: Intel IOMMU: Assigning IGD device: 00:02.1 on some machines, 
>> causes Xen to freeze for >2mins because of RMRR mappings
>>
>> Can u please guid me a little bit, on how to write such function which
>> will work on a batch of pages?
>> Should i just enclose the:
>> "
>> ...
>>    pg_maddr = addr_to_dma_page_maddr(d, (paddr_t)gfn << PAGE_SHIFT_4K, 1);
>>    if ( pg_maddr == 0 )
>>    {
>>        spin_unlock(&hd->mapping_lock);
>>        return -ENOMEM;
>>    }
>>    page = (struct dma_pte *)map_vtd_domain_page(pg_maddr);
>>    pte = page + (gfn & LEVEL_MASK);
>>    pte_present = dma_pte_present(*pte);
>>    dma_set_pte_addr(*pte, (paddr_t)mfn << PAGE_SHIFT_4K);
>>    dma_set_pte_prot(*pte, DMA_PTE_READ | DMA_PTE_WRITE);
>>
>>    /* Set the SNP on leaf page table if Snoop Control available */
>>    if ( iommu_snoop )
>>        dma_set_pte_snp(*pte);
>> ...
>> "
>>
>> in a loop?
>>
>> On Mon, Nov 30, 2009 at 4:30 AM, Han, Weidong <weidong.han@xxxxxxxxx> wrote:
>>> Tom,
>>>
>>> Yes, you can add an API to map batches of pages instead of mapping each 
>>> page in a separate call.
>>>
>>> RMRR regions of USB controller is ignored because they won't be used in 
>>> guest. The RMRR 0x7dc00000 to 0x80000000 is shared by 00:02.0 and 00:02.1, 
>>> it will be used by IGD in guest. But you can have a try to ignore it for 
>>> 00:02.1.
>>>
>>>
>>> Regards,
>>> Weidong
>>>
>>> -----Original Message-----
>>> From: Tom Rotenberg [mailto:tom.rotenberg@xxxxxxxxx]
>>> Sent: Monday, November 30, 2009 1:56 AM
>>> To: xen-devel@xxxxxxxxxxxxxxxxxxx
>>> Cc: Han, Weidong
>>> Subject: Intel IOMMU: Assigning IGD device: 00:02.1 on some machines, 
>>> causes Xen to freeze for >2mins because of RMRR mappings
>>>
>>> Hi All,
>>>
>>> I am using a Dell E6400 machine, with IGD (Intel graphics device),
>>> which i'm trying to pass-through into a domU with Windows XP. When i
>>> assign only the 00:02.0 device, it seems to work ok, but when i try to
>>> assign the 00:02.1 device, the whole machine seems to freeze form more
>>> then 2 mins, causing a lot of messgaes in dom0, such as: SATA doesn't
>>> respond, etc.
>>>
>>> After some analysis i made, i discovered the followings:
>>> * When calling the (Intel) iommu_assign_device, it checks if the
>>> device has any details in the RMRR table, and if so it calls the
>>> 'iommu_prepare_rmrr_dev()' function.
>>> * The device 00:02.1 has an RMRR information, which details the whole
>>> area between:  0x7dc00000 to 0x80000000  (it contains ~9000 pages)
>>> * For each such page, Xen calls the 'intel_iommu_map_page()' function.
>>> This causes the hypercall to take a lot of time to process, and this
>>> makes dom0 to stop getting responds from devices, such as SATA, etc,,
>>> which may lead to a whole system  crash.
>>>
>>> My question are:
>>> 1. Can this hypercall be in some way preemptive, so it won't stuck the
>>> whole system (i noticed that there are other hypercalls, which are
>>> preemptive) ?
>>> 2. Why can't the mapping of the pages, be done in batches of pages,
>>> instead of mapping each page in a separate call to
>>> 'intel_iommu_map_page()' ?
>>> 3. i noticed that for USB devices, the code there ignores the USB
>>> RMRR... can this be done also for the 00:02.1 device?
>>>
>>> Tom
>>>
>>
>

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