Hi Alex
On 2025/11/18 05:39, Alex Bennée wrote:
Tao Tang <[email protected]> writes:
Hi Clement,
On 2025/11/13 15:02, CLEMENT MATHIEU--DRIF wrote:
Hi Tao,
On Thu, 2025-11-13 at 00:21 +0800, Tao Tang wrote:
Add a minimal PCI test device designed to exercise IOMMU translation
(such as ARM SMMUv3) without requiring guest firmware or OS. The device
provides MMIO registers to configure and trigger DMA operations with
controllable attributes (security state, address space), enabling
deterministic IOMMU testing.
Key features:
- Bare-metal IOMMU testing via simple MMIO interface
- Configurable DMA attributes for security states and address spaces
- Write-then-read verification pattern with automatic result checking
The device performs a deterministic DMA test pattern: write a known
value(0x88888888) to a configured IOVA, read it back, and verify data
integrity. Results are reported through a dedicated result register,
eliminating the need for complex interrupt handling or driver
infrastructure in tests.
This is purely a test device and not intended for production use or
machine realism. It complements existing test infrastructure like
pci-testdev but focuses specifically on IOMMU translation path
validation.
Signed-off-by: Tao Tang
<[[email protected]](mailto:[email protected])>
---
docs/specs/index.rst | 1 +
docs/specs/iommu-testdev.rst | 96 +++++++++++
hw/misc/Kconfig | 5 +
hw/misc/iommu-testdev.c | 292 ++++++++++++++++++++++++++++++++
hw/misc/meson.build | 1 +
hw/misc/trace-events | 10 ++
include/hw/misc/iommu-testdev.h | 78 +++++++++
7 files changed, 483 insertions(+)
create mode 100644 docs/specs/iommu-testdev.rst
create mode 100644 hw/misc/iommu-testdev.c
create mode 100644 include/hw/misc/iommu-testdev.h
------------------------------<snip>------------------------------
------------------------------<snip>------------------------------
+
+static void iommu_testdev_maybe_run_dma(IOMMUTestDevState *s)
+{
+ int i, j, remaining_bytes;
I think i and j could be declared in their respective loop
Thanks a lot for taking the time to review the patch. All your
suggestions are excellent and make a lot of sense.
Move the i and j loop variable declarations into their respective for
loops sounds a good idea. But I wasn't entirely sure if QEMU had a
strict code style requirement for this, such as mandating all
variables be defined at the start of the function before any
executable code (C89 style), so I appreciate the clarification.
<snip>
We have a special exemption, from style.rst:
Mixed declarations (interleaving statements and declarations within
blocks) are generally not allowed; declarations should be at the beginning
of blocks. To avoid accidental re-use it is permissible to declare
loop variables inside for loops:
.. code-block:: c
for (int i = 0; i < ARRAY_SIZE(thing); i++) {
/* do something loopy */
}
Every now and then, an exception is made for declarations inside a
#ifdef or #ifndef block: if the code looks nicer, such declarations can
be placed at the top of the block even if there are statements above.
On the other hand, however, it's often best to move that #ifdef/#ifndef
block to a separate function altogether.
Thanks for the clarification and the pointer to style.rst.
Good to know for (int i = ...) is explicitly allowed — I’ll update the
patch to declare the loop variables in the for headers in v4.
Best regards,
Tao
