Re: [PATCH v3 0/5] ACPI: DMA ranges management

From: Nate Watterson
Date: Thu Aug 03 2017 - 11:45:18 EST

Hi Lorenzo,

On 8/3/2017 8:32 AM, Lorenzo Pieralisi wrote:
This patch series is v3 of a previous posting:

- Fixed DMA masks computation
- Fixed size computation overflow in acpi_dma_get_range()

- Reworked acpi_dma_get_range() flow and logs
- Added IORT named component address limits
- Renamed acpi_dev_get_resources() helper function
- Rebased against v4.13-rc3


-- Original cover letter --

As reported in:

the bus connecting devices to an IOMMU bus can be smaller in size than
the IOMMU input address bits which results in devices DMA HW bugs in
particular related to IOVA allocation (ie chopping of higher address
bits owing to system bus HW capabilities mismatch with the IOMMU).

Fortunately this problem can be solved through an already present but never
used ACPI 6.2 firmware bindings (ie _DMA object) allowing to define the DMA
window for a specific bus in ACPI and therefore all upstream devices
connected to it.

This small patch series enables _DMA parsing in ACPI core code and
use it in ACPI IORT code in order to detect DMA ranges for devices and
update their data structures to make them work with their related DMA
addressing restrictions.

Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
Cc: Feng Kan <fkan@xxxxxxx>
Cc: Jon Masters <jcm@xxxxxxxxxx>
Cc: Robert Moore <robert.moore@xxxxxxxxx>
Cc: Robin Murphy <robin.murphy@xxxxxxx>
Cc: Zhang Rui <rui.zhang@xxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>

Lorenzo Pieralisi (5):
ACPICA: resource_mgr: Allow _DMA method in walk resources
ACPI: Make acpi_dev_get_resources() method agnostic
ACPI: Introduce DMA ranges parsing
ACPI: Make acpi_dma_configure() DMA regions aware
ACPI/IORT: Add IORT named component memory address limits

drivers/acpi/acpica/rsxface.c | 7 ++--
drivers/acpi/arm64/iort.c | 57 ++++++++++++++++++++++++++-
drivers/acpi/resource.c | 82 +++++++++++++++++++++++++++++---------
drivers/acpi/scan.c | 91 +++++++++++++++++++++++++++++++++++++++----
include/acpi/acnames.h | 1 +
include/acpi/acpi_bus.h | 2 +
include/linux/acpi.h | 8 ++++
include/linux/acpi_iort.h | 5 ++-
8 files changed, 219 insertions(+), 34 deletions(-)

I tested with named components and with _DMA objects at a variety of
sizes and verified the configured masks matched the expected values.

Tested-by: Nate Watterson <nwatters@xxxxxxxxxxxxxx>

One general question I had while testing the patch is whether it is
possible to define a complete 64-bit range using the _DMA method. For
instance, to get a 64-bit dma_mask I had to use a non-zero MIN value
so that LEN would not overflow.

PosDecode, // _DEC
MinFixed, // _MIF
MaxFixed, // _MAF
Prefetchable, // _MEM
ReadWrite, // _RW
0, // _GRA
0x1000, // _MIN
0xffffffffffffffff, // _MAX
0x0, // _TRA
0xfffffffffffff000, // _LEN


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