Hi Nicolas, On Thu, Jan 30, 2025 at 10:59:56AM -0500, Nicolas Dufresne wrote: > Le jeudi 30 janvier 2025 à 14:46 +0100, Maxime Ripard a écrit : > > Hi, > > > > I started to review it, but it's probably best to discuss it here. > > > > On Thu, Jan 30, 2025 at 01:08:56PM +0000, Florent Tomasin wrote: > > > Hi, > > > > > > This is a patch series covering the support for protected mode execution in > > > Mali Panthor CSF kernel driver. > > > > > > The Mali CSF GPUs come with the support for protected mode execution at the > > > HW level. This feature requires two main changes in the kernel driver: > > > > > > 1) Configure the GPU with a protected buffer. The system must provide a DMA > > > heap from which the driver can allocate a protected buffer. > > > It can be a carved-out memory or dynamically allocated protected memory region. > > > Some system includes a trusted FW which is in charge of the protected memory. > > > Since this problem is integration specific, the Mali Panthor CSF kernel > > > driver must import the protected memory from a device specific exporter. > > > > Why do you need a heap for it in the first place? My understanding of > > your series is that you have a carved out memory region somewhere, and > > you want to allocate from that carved out memory region your buffers. > > > > How is that any different from using a reserved-memory region, adding > > the reserved-memory property to the GPU device and doing all your > > allocation through the usual dma_alloc_* API? > > How do you then multiplex this region so it can be shared between > GPU/Camera/Display/Codec drivers and also userspace ? You could point all the devices to the same reserved memory region, and they would all allocate from there, including for their userspace-facing allocations. > Also, how the secure memory is allocted / obtained is a process that > can vary a lot between SoC, so implementation details assumption > should not be coded in the driver. But yeah, we agree there, it's also the point I was trying to make :) Maxime
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