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Date: Mon, 18 Mar 2024 10:58:46 -0700
From: Jerry Snitselaar <jsnitsel@redhat.com>
To: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>, linux-crypto@vger.kernel.org, 
	linux-doc@vger.kernel.org
Subject: Re: [PATCH] crypto: iaa: Fix some errors in IAA documentation
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On Mon, Mar 18, 2024 at 11:26:31AM -0500, Tom Zanussi wrote:
> Hi Jerry,
> 
> On Mon, 2024-03-18 at 00:49 -0700, Jerry Snitselaar wrote:
> > On Sun, Mar 17, 2024 at 11:44:21PM -0700, Jerry Snitselaar wrote:
> > > This cleans up the following issues I ran into when trying to use
> > > the
> > > scripts and commands in the iaa-crypto.rst document.
> > > 
> > > - Fix incorrect arguments being passed to accel-config
> > > ? config-wq.
> > > ??? - Replace --device_name with --driver-name.
> > > ??? - Replace --driver_name with --driver-name.
> > > ??? - Replace --size with --wq-size.
> > > ??? - Add missing --priority argument.
> > > - Add missing accel-config config-engine command after the
> > > ? config-wq commands.
> > > - Fix wq name passed to accel-config config-wq.
> > > - Add rmmod/modprobe of iaa_crypto to script that disables,
> > > ? then enables all devices and workqueues to avoid enable-wq
> > > ? failing with -EEXIST when trying to register to compression
> > > ? algorithm.
> > > - Fix device name in cases where iaa was used instead of iax.
> > > 
> > > Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
> > > Cc: Jonathan Corbet <corbet@lwn.net>
> > > Cc: linux-crypto@vger.kernel.org
> > > Cc: linux-doc@vger.kernel.org
> > > Signed-off-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > > ---
> > > ?.../driver-api/crypto/iaa/iaa-crypto.rst????? | 22 ++++++++++++++-
> > > ----
> > > ?1 file changed, 16 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/Documentation/driver-api/crypto/iaa/iaa-crypto.rst
> > > b/Documentation/driver-api/crypto/iaa/iaa-crypto.rst
> > > index de587cf9cbed..330d35df5f16 100644
> > > --- a/Documentation/driver-api/crypto/iaa/iaa-crypto.rst
> > > +++ b/Documentation/driver-api/crypto/iaa/iaa-crypto.rst
> > > @@ -179,7 +179,9 @@ has the old 'iax' device naming in place) ::
> > > ?
> > > ?? # configure wq1.0
> > > ?
> > > -? accel-config config-wq --group-id=0 --mode=dedicated --
> > > type=kernel --name="iaa_crypto" --device_name="crypto" iax1/wq1.0
> > > +? accel-config config-wq --group-id=0 --mode=dedicated --
> > > type=kernel --priority=10 --name="iaa_crypto" --driver-
> > > name="crypto" iax1/wq1.0
> > > +
> > > +? accel-config config-engine iax1/engine1.0 --group-id=0
> > > ?
> > > ?? # enable IAA device iax1
> > > ?
> > > @@ -536,12 +538,20 @@ The below script automatically does that::
> > > ?
> > > ?? echo "End Disable IAA"
> > > ?
> > > +? echo "Reload iaa_crypto module"
> > > +
> > > +? rmmod iaa_crypto
> > > +? modprobe iaa_crypto
> > > +
> > > +? echo "End Reload iaa_crypto module"
> > > +
> > > ?? #
> > > ?? # configure iaa wqs and devices
> > > ?? #
> > > ?? echo "Configure IAA"
> > > ?? for ((i = 1; i < ${num_iaa} * 2; i += 2)); do
> > > -????? accel-config config-wq --group-id=0 --mode=dedicated --
> > > size=128 --priority=10 --type=kernel --name="iaa_crypto" --
> > > driver_name="crypto" iax${i}/wq${i}
> > > +????? accel-config config-wq --group-id=0 --mode=dedicated --wq-
> > > size=128 --priority=10 --type=kernel --name="iaa_crypto" --driver-
> > > name="crypto" iax${i}/wq${i}.0
> > > +????? accel-config config-engine iax${i}/engine${i}.0 --group-id=0
> > > ?? done
> > > ?
> > > ?? echo "End Configure IAA"
> > > @@ -552,10 +562,10 @@ The below script automatically does that::
> > > ?? echo "Enable IAA"
> > > ?
> > > ?? for ((i = 1; i < ${num_iaa} * 2; i += 2)); do
> > > -????? echo enable iaa iaa${i}
> > > -????? accel-config enable-device iaa${i}
> > > -????? echo enable wq iaa${i}/wq${i}.0
> > > -????? accel-config enable-wq iaa${i}/wq${i}.0
> > > +????? echo enable iaa iax${i}
> > > +????? accel-config enable-device iax${i}
> > > +????? echo enable wq iax${i}/wq${i}.0
> > > +????? accel-config enable-wq iax${i}/wq${i}.0
> > > ?? done
> > > ?
> > > ?? echo "End Enable IAA"
> > > -- 
> > > 2.41.0
> > > 
> > 
> > In addition to the above, the sections related to the modes seem
> > to be off to me.
> > 
> > Legacy mode in the Intel IOMMU context is when the IOMMU does not
> > have
> > scalable mode enabled. If you pass intel_iommu=off the Intel IOMMU
> > will not be initialized, and I think that would correspond to the No
> > IOMMU
> > mode instead of Legacy mode. The other suggestion for Legacy mode of
> > disabling VT-d in the BIOS would also be No IOMMU mode, but in
> > addition to the dma remapping units being disabled it would disable
> > interrupt remapping since the DMAR table would no longer be presented
> > to the OS by the BIOS.
> > 
> > I think the modes should be:
> > 
> > Scalable mode: intel_iommu=on,sm_on
> > Legacy mode: intel_iommu=on
> > No IOMMU mode: intel_iommu=off (or VT-d disabled in BIOS)
> > 
> 
> Yes, I think you're correct, those make more sense.
> 
> > Since Intel IOMMU and scabale mode have config options that allow
> > them
> > to be enabled by default, there are different parameter variations
> > that would match the above cases. I don't know if they need to
> > be detailed here, or if it would just make it more confusing.
> > 
> 
> Personally, I think it would be useful to have them detailed and might
> lessen confusion for people setting things up and/or debugging a setup.
> 
> Thanks,
> 
> Tom

Hi Tom,

This is what I came up with last night for the kernel parameters when thinking about it:


| mode \ default enable | intel_iommu + /sm + | intel_iommu + / sm - | intel_iommu - / sm +  | intel_iommu - / sm - |
|-----------------------+---------------------+----------------------+-----------------------+----------------------|
| Scalable Mode         | nothing             | intel_iommu=sm_on    | intel_iommu=on        | intel_iommu=on,sm_on |
| Legacy Mode           | intel_iommu=sm_off  | nothing              | intel_iommu=on,sm_off | intel_iommu=on       |
| No IOMMU Mode         | intel_iommu=off     | intel_iommu=off      | nothing               | nothing              |


Regards,
Jerry


> 
> > Regards,
> > Jerry
> > 
>