Re: [Xen-devel] [PATCH v2 07/13] iommu: Make decision about needing IOMMU for hardware domains in advance

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.12.17 at 20:23, <olekstysh@xxxxxxxxx> wrote:
> On Wed, Dec 6, 2017 at 7:01 PM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>>> On 25.07.17 at 19:26, <olekstysh@xxxxxxxxx> wrote:
>>> @@ -175,37 +182,6 @@ void __hwdom_init iommu_hwdom_init(struct domain *d)
>>>          return;
>>>
>>>      register_keyhandler('o', &iommu_dump_p2m_table, "dump iommu p2m 
>>> table", 0);
>>> -    d->need_iommu = !!iommu_dom0_strict;
>>> -    if ( need_iommu(d) && !iommu_use_hap_pt(d) )
>>> -    {
>>> -        struct page_info *page;
>>> -        unsigned int i = 0;
>>> -        int rc = 0;
>>> -
>>> -        page_list_for_each ( page, &d->page_list )
>>> -        {
>>> -            unsigned long mfn = page_to_mfn(page);
>>> -            unsigned long gfn = mfn_to_gmfn(d, mfn);
>>> -            unsigned int mapping = IOMMUF_readable;
>>> -            int ret;
>>> -
>>> -            if ( ((page->u.inuse.type_info & PGT_count_mask) == 0) ||
>>> -                 ((page->u.inuse.type_info & PGT_type_mask)
>>> -                  == PGT_writable_page) )
>>> -                mapping |= IOMMUF_writable;
>>> -
>>> -            ret = hd->platform_ops->map_pages(d, gfn, mfn, 0, mapping);
>>> -            if ( !rc )
>>> -                rc = ret;
>>> -
>>> -            if ( !(i++ & 0xfffff) )
>>> -                process_pending_softirqs();
>>> -        }
>>> -
>>> -        if ( rc )
>>> -            printk(XENLOG_WARNING "d%d: IOMMU mapping failed: %d\n",
>>> -                   d->domain_id, rc);
>>> -    }
>>>
>>>      return hd->platform_ops->hwdom_init(d);
>>>  }
>>
>> Just to double check - this change was tested on x86 Dom0, at
>> least PV (for PVH I'd at least expect that you've did some static
>> code analysis to make sure this doesn't put in further roadblocks)?
> 
> I am afraid I didn't get the second part of this sentence.

Understandably, since I've broken grammar in the course of
re-phrasing a number of times before sending. Dom0 PVH isn't
complete at this point, so I can't ask you to actually test it. But
I want to be reasonably certain that the change you make won't
further complicate this enabling work (you may want to also Cc
Roger on future versions of the patch for this very reason), the
more that on AMD we've been unconditionally using non-shared
page tables for quite some time. (In fact I see chances that the
change might actually help the time it takes to set up PVH Dom0,
especially when a sufficiently large chunk of memory is being
handed to it.)

Jan


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