On Fri, 10 Jul 2026 at 14:15, Alex Bennée <[email protected]> wrote:
>
> The datasheet doesn't explicitly say that TXFR_LEN has to be word
> aligned but the fact there is a DMA_D_WIDTH flag to select between 32
> bit and 128 bit strongly implies that is how it works. The downstream
> rpi kernel also goes to efforts to not write sub-4 byte lengths so
> lets:
>
> - fail when mis-programmed and report GUEST_ERROR
> - catch setting D_WIDTH for 128 bit and report UNIMP
> - add comments that the DEBUG register isn't a straight write
You dropped the comments in v2, so I've dropped this line from
the commit message.
> Yodel did some digging into the specs (see discussion link):
>
> {A} AMBA AXI Protocol Version: 2.0 Specification
> https://documentation-service.arm.com/static/64256e84314e245d086bc88f
>
> {B} BCM2835 ARM Peripherals
> https://datasheets.raspberrypi.com/bcm2835/bcm2835-peripherals.pdf
>
> [1] {A} (p. 10-2)
> [2] {B} (p. 51)
> [3] {A} (p. 14-5)
> [4] {A} (p. 4-3)
> [5] {A} (p. 9-4)
> [6] {B} (p. 53)
>
> However was unable to come up with an unambiguous conclusion without
> testing on the real hardware. So in the absence of certainty and for
> the sake of addressing the DoS I suggest we merge as is for now.
>
> Link:
> https://lore.kernel.org/all/[email protected]/
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/3201
> Signed-off-by: Alex Bennée <[email protected]>
>
Applied to target-arm.next, thanks.
-- PMM
