On 12/04/2012 05:53:33 AM, Sethi Varun-B16395 wrote:
=20
=20
quoted
-----Original Message-----
From: Wood Scott-B07421
Sent: Monday, December 03, 2012 10:34 PM
To: Sethi Varun-B16395
Cc: Joerg Roedel; linux-kernel@vger.kernel.org; iommu@lists.linux-
foundation.org; Wood Scott-B07421; linuxppc-dev@lists.ozlabs.org; =20
Tabi
quoted
Timur-B04825
Subject: Re: [PATCH 3/4 v5] iommu/fsl: Add iommu domain attributes
required by fsl PAMU driver.
On 12/03/2012 10:57:29 AM, Sethi Varun-B16395 wrote:
quoted
quoted
-----Original Message-----
From: iommu-bounces@lists.linux-foundation.org [mailto:iommu-
bounces@lists.linux-foundation.org] On Behalf Of Joerg Roedel
Sent: Sunday, December 02, 2012 7:33 PM
To: Sethi Varun-B16395
Cc: linux-kernel@vger.kernel.org; =20
iommu@lists.linux-foundation.org;
quoted
quoted
Wood
quoted
Scott-B07421; linuxppc-dev@lists.ozlabs.org; Tabi Timur-B04825
Subject: Re: [PATCH 3/4 v5] iommu/fsl: Add iommu domain =20
attributes
quoted
quoted
quoted
required by fsl PAMU driver.
Hmm, we need to work out a good abstraction for this.
On Tue, Nov 20, 2012 at 07:24:56PM +0530, Varun Sethi wrote:
quoted
Added the following domain attributes required by FSL PAMU =20
driver:
quoted
quoted
quoted
quoted
1. Subwindows field added to the iommu domain geometry =20
attribute.
quoted
quoted
quoted
Are the Subwindows mapped with full size or do you map only =20
parts
quoted
quoted
of the
quoted
subwindows?
[Sethi Varun-B16395] It's possible to map a part of the subwindow =20
i.e.
quoted
quoted
size of the mapping can be less than the sub window size.
quoted
quoted
+ * This attribute indicates number of DMA subwindows
supported
quoted
by
quoted
quoted
+ * the geometry. If there is a single window that maps =20
the
quoted
quoted
entire
quoted
quoted
+ * geometry, attribute must be set to "1". A value of =20
"0"
quoted
quoted
implies
quoted
quoted
+ * that this mechanism is not used at all(normal paging =20
is
quoted
quoted
used).
quoted
quoted
+ * Value other than* "0" or "1" indicates the actual =20
number
quoted
of
quoted
quoted
quoted
+ * subwindows.
+ */
This semantic is ugly, how about a feature detection mechanism?
[Sethi Varun-B16395] A feature mechanism to query the type of =20
IOMMU?
quoted
A feature mechanism to determine whether this subwindow mechanism is
available, and what the limits are.
So, we use the IOMMU capability interface to find out if IOMMU =20
supports sub windows or not, right? But still number of sub windows =20
would be specified as a part of the geometry and the valid value for =20
sub windows would 0,1 or actual number of sub windows.
How does a user of the interface find out what values are possible for =20
the "actual number of subwindows"? How does a user of the interface =20
find out whether there are any limitations on specifying a value of =20
zero (in the case of PAMU, that would be a maximum 1 MiB =20
naturally-aligned aperture to support arbitrary 4KiB mappings)?
-Scott=
-----Original Message-----
From: Wood Scott-B07421
Sent: Tuesday, December 04, 2012 11:53 PM
To: Sethi Varun-B16395
Cc: Wood Scott-B07421; Joerg Roedel; linux-kernel@vger.kernel.org;
iommu@lists.linux-foundation.org; linuxppc-dev@lists.ozlabs.org; Tabi
Timur-B04825
Subject: Re: [PATCH 3/4 v5] iommu/fsl: Add iommu domain attributes
required by fsl PAMU driver.
=20
On 12/04/2012 05:53:33 AM, Sethi Varun-B16395 wrote:
quoted
quoted
-----Original Message-----
From: Wood Scott-B07421
Sent: Monday, December 03, 2012 10:34 PM
To: Sethi Varun-B16395
Cc: Joerg Roedel; linux-kernel@vger.kernel.org; iommu@lists.linux-
foundation.org; Wood Scott-B07421; linuxppc-dev@lists.ozlabs.org;
Tabi
quoted
Timur-B04825
Subject: Re: [PATCH 3/4 v5] iommu/fsl: Add iommu domain attributes
required by fsl PAMU driver.
On 12/03/2012 10:57:29 AM, Sethi Varun-B16395 wrote:
quoted
quoted
-----Original Message-----
From: iommu-bounces@lists.linux-foundation.org [mailto:iommu-
bounces@lists.linux-foundation.org] On Behalf Of Joerg Roedel
Sent: Sunday, December 02, 2012 7:33 PM
To: Sethi Varun-B16395
Cc: linux-kernel@vger.kernel.org;
iommu@lists.linux-foundation.org;
quoted
quoted
Wood
quoted
Scott-B07421; linuxppc-dev@lists.ozlabs.org; Tabi Timur-B04825
Subject: Re: [PATCH 3/4 v5] iommu/fsl: Add iommu domain
attributes
quoted
quoted
quoted
required by fsl PAMU driver.
Hmm, we need to work out a good abstraction for this.
On Tue, Nov 20, 2012 at 07:24:56PM +0530, Varun Sethi wrote:
quoted
Added the following domain attributes required by FSL PAMU
driver:
quoted
quoted
quoted
quoted
1. Subwindows field added to the iommu domain geometry
attribute.
quoted
quoted
quoted
Are the Subwindows mapped with full size or do you map only
parts
quoted
quoted
of the
quoted
subwindows?
[Sethi Varun-B16395] It's possible to map a part of the subwindow
i.e.
quoted
quoted
size of the mapping can be less than the sub window size.
quoted
quoted
+ * This attribute indicates number of DMA subwindows
supported
quoted
by
quoted
quoted
+ * the geometry. If there is a single window that maps
the
quoted
quoted
entire
quoted
quoted
+ * geometry, attribute must be set to "1". A value of
"0"
quoted
quoted
implies
quoted
quoted
+ * that this mechanism is not used at all(normal paging
is
quoted
quoted
used).
quoted
quoted
+ * Value other than* "0" or "1" indicates the actual
number
quoted
of
quoted
quoted
quoted
+ * subwindows.
+ */
This semantic is ugly, how about a feature detection mechanism?
[Sethi Varun-B16395] A feature mechanism to query the type of
IOMMU?
quoted
A feature mechanism to determine whether this subwindow mechanism is
available, and what the limits are.
So, we use the IOMMU capability interface to find out if IOMMU
supports sub windows or not, right? But still number of sub windows
would be specified as a part of the geometry and the valid value for
sub windows would 0,1 or actual number of sub windows.
=20
How does a user of the interface find out what values are possible for
the "actual number of subwindows"? How does a user of the interface find
out whether there are any limitations on specifying a value of zero (in
the case of PAMU, that would be a maximum 1 MiB naturally-aligned
aperture to support arbitrary 4KiB mappings)?
How about if we say that the default value for subwindows is zero and this =
what you get when you read the geometry (iommu_get_attr) after initializing=
the domain? In that case the user would know that implication of setting s=
ubwindows to zero with respect to the aperture size. Also, should we introd=
uce an additional API like "iommu_check_attr", which the user can use to va=
lidate the attribute value. For example in case of geometry, the user can f=
ill up the structure and pass it to the iommu driver in order to verify the=
aperture and subwindows field.
-Varun