Re: [PATCH v2 3/7] iommu/vt-d: Expose ISA direct mapping region via iommu_get_resv_regions

[Lu Baolu]

Hi James,

I did a sanity test from my end. The test machine fails to boot. I
haven't seen any valuable kernel log. It results in a purple screen.

Best regards,
Lu Baolu

On 3/29/19 11:26 PM, James Sewart wrote:
> Hey Lu,
>
> Iâve attached a preliminary v3, if you could take a look and run some tests
> that would be great.
>
> Since v2 iâve added your default domain type patches, the new device_group
> handler, and incorporated Jacobâs feedback.
>
> > On 28 Mar 2019, at 18:37, James Sewart <jamessewart@xxxxxxxxxx> wrote:
> >
> > Hey Lu,
> >
> > > On 26 Mar 2019, at 01:24, Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:
> > >
> > > Hi James,
> > >
> > > On 3/25/19 8:57 PM, James Sewart wrote:
> > > > > > Theres an issue that if we choose to alloc a new resv_region with type
> > > > > > IOMMU_RESV_DIRECT, we will need to refactor intel_iommu_put_resv_regions
> > > > > > to free this entry type which means refactoring the rmrr regions in
> > > > > > get_resv_regions. Should this work be in this patchset?
> > > > > Do you mean the rmrr regions are not allocated in get_resv_regions, but
> > > > > are freed in put_resv_regions? I think we should fix this in this patch
> > > > > set since this might impact the device passthrough if we don't do it.
> > > > Theyâre not allocated and not freed currently, only type IOMMU_RESV_MSI is
> > > > freed in put_resv_regions. If we allocate a new resv_region with type
> > > > IOMMU_RESV_DIRECT for the isa region, then it wonât be freed. If we modify
> > > > put_resv_regions to free type IOMMU_RESV_DIRECT, then we will try to free
> > > > the static RMRR regions.
> > > > Either the ISA region is static and not freed as with my implementation,
> > > > or the RMRR regions are converted to be allocated on each call to
> > > > get_resv_regions and freed in put_resv_regions.
> > >
> > > By the way, there's another way in my mind. Let's add a new region type
> > > for LPC devices, e.x. IOMMU_RESV_LPC, and then handle it in the same way
> > > as those MSI regions. Just FYI.
> >
> > This solution would require adding some extra code to
> > iommu_group_create_direct_mappings as currently only type
> > IOMMU_RESV_DIRECT is identity mapped, other types are only reserved.
> >
> >
> > > Best regards,
> > > Lu Baolu
> >
> > Cheers,
> > James.
>
> Cheers,
> James.