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From: David Christensen <drc@linux.vnet.ibm.com>
To: linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v6 00/11] DDW + Indirect Mapping
Date: Mon, 30 Aug 2021 10:48:49 -0700	[thread overview]
Message-ID: <82ca56ab-6a0a-7cbb-a5e7-facc40f35c3c@linux.vnet.ibm.com> (raw)
In-Reply-To: <20210817063929.38701-1-leobras.c@gmail.com>



On 8/16/21 11:39 PM, Leonardo Bras wrote:
> So far it's assumed possible to map the guest RAM 1:1 to the bus, which
> works with a small number of devices. SRIOV changes it as the user can
> configure hundreds VFs and since phyp preallocates TCEs and does not
> allow IOMMU pages bigger than 64K, it has to limit the number of TCEs
> per a PE to limit waste of physical pages.
> 
> As of today, if the assumed direct mapping is not possible, DDW creation
> is skipped and the default DMA window "ibm,dma-window" is used instead.
> 
> Using the DDW instead of the default DMA window may allow to expand the
> amount of memory that can be DMA-mapped, given the number of pages (TCEs)
> may stay the same (or increase) and the default DMA window offers only
> 4k-pages while DDW may offer larger pages (4k, 64k, 16M ...).

So if I'm reading this correctly, VFIO applications requiring hugepage 
DMA mappings (e.g. 16M or 2GB) can be supported on an LPAR or DLPAR 
after this change, is that correct?  Any limitations based on processor 
or pHyp revision levels?

Dave

  parent reply	other threads:[~2021-08-30 17:49 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-17  6:39 [PATCH v6 00/11] DDW + Indirect Mapping Leonardo Bras
2021-08-17  6:39 ` [PATCH v6 01/11] powerpc/pseries/iommu: Replace hard-coded page shift Leonardo Bras
2021-08-17  6:39 ` [PATCH v6 02/11] powerpc/kernel/iommu: Add new iommu_table_in_use() helper Leonardo Bras
2021-08-27 16:52   ` Frederic Barrat
2021-08-17  6:39 ` [PATCH v6 03/11] powerpc/pseries/iommu: Add iommu_pseries_alloc_table() helper Leonardo Bras
2021-08-17  6:39 ` [PATCH v6 04/11] powerpc/pseries/iommu: Add ddw_list_new_entry() helper Leonardo Bras
2021-08-17  6:39 ` [PATCH v6 05/11] powerpc/pseries/iommu: Allow DDW windows starting at 0x00 Leonardo Bras
2021-08-17  6:39 ` [PATCH v6 06/11] powerpc/pseries/iommu: Add ddw_property_create() and refactor enable_ddw() Leonardo Bras
2021-08-27 16:55   ` Frederic Barrat
2021-08-17  6:39 ` [PATCH v6 07/11] powerpc/pseries/iommu: Reorganize iommu_table_setparms*() with new helper Leonardo Bras
2021-08-17  6:39 ` [PATCH v6 08/11] powerpc/pseries/iommu: Update remove_dma_window() to accept property name Leonardo Bras
2021-08-27 16:58   ` Frederic Barrat
2021-08-17  6:39 ` [PATCH v6 09/11] powerpc/pseries/iommu: Find existing DDW with given " Leonardo Bras
2021-08-17  6:39 ` [PATCH v6 10/11] powerpc/pseries/iommu: Make use of DDW for indirect mapping Leonardo Bras
2021-08-27 17:06   ` Frederic Barrat
2021-08-27 17:53     ` Leonardo Brás
2021-08-17  6:39 ` [PATCH v6 11/11] powerpc/pseries/iommu: Rename "direct window" to "dma window" Leonardo Bras
2021-08-30 17:48 ` David Christensen [this message]
2021-08-31 20:18   ` [PATCH v6 00/11] DDW + Indirect Mapping Leonardo Brás
2021-08-31 20:18     ` Leonardo Brás
2021-08-31 20:39     ` David Christensen
2021-08-31 20:49       ` Leonardo Brás
2021-08-31 20:49         ` Leonardo Brás
2021-08-31 13:56 ` Michael Ellerman
2021-08-31 13:56   ` Michael Ellerman

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