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From: "Leonardo Brás" <leobras.c@gmail.com>
To: David Christensen <drc@linux.vnet.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Alexey Kardashevskiy <aik@ozlabs.ru>,
David Gibson <david@gibson.dropbear.id.au>,
kernel test robot <lkp@intel.com>,
Nicolin Chen <nicoleotsuka@gmail.com>,
Frederic Barrat <fbarrat@linux.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 00/11] DDW + Indirect Mapping
Date: Tue, 31 Aug 2021 17:49:36 -0300 [thread overview]
Message-ID: <dc80ad61dbd52a3fda5cd47ab5e60e45009b511d.camel@gmail.com> (raw)
In-Reply-To: <311ece8f-bedc-b3f7-0d1b-2cb78438890f@linux.vnet.ibm.com>
On Tue, 2021-08-31 at 13:39 -0700, David Christensen wrote:
> >
> > This series allow Indirect DMA using DDW when available, which
> > usually
> > means bigger pagesizes and more TCEs, and so more DMA space.
>
> How is the mapping method selected? LPAR creation via the HMC, Linux
> kernel load parameter, or some other method?
At device/bus probe, if there is enough DMA space available for Direct
DMA, then it's used. If not, it uses indirect DMA.
>
> The hcall overhead doesn't seem too worrisome when mapping 1GB pages
> so
> the Indirect DMA method might be best in my situation (DPDK).
Well, it depends on usage.
I mean, the recommended use of IOMMU is to map, transmit and then
unmap, but this will vary on the implementation of the driver.
If, for example, there is some reuse of the DMA mapping, as in a
previous patchset I sent (IOMMU Pagecache), then the hcall overhead can
be reduced drastically.
>
> Dave
Best regards,
Leonardo
prev parent reply other threads:[~2021-08-31 20:49 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-17 6:39 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
2021-08-31 13:56 ` [PATCH v6 00/11] DDW + Indirect Mapping Michael Ellerman
[not found] ` <82ca56ab-6a0a-7cbb-a5e7-facc40f35c3c@linux.vnet.ibm.com>
2021-08-31 20:18 ` Leonardo Brás
2021-08-31 20:39 ` David Christensen
2021-08-31 20:49 ` Leonardo Brás [this message]
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