Re: framebuffer corruption due to overlapping stp instructions on arm64

[Mikulas Patocka]

On Mon, 6 Aug 2018, Ard Biesheuvel wrote:

> No that works fine for me. VDPAU acceleration works as well, but it
> depends on your chromium build whether it can actually use it, I
> think? In any case, mplayer can use vdpau to play 1080p h264 without
> breaking a sweat on this system.
> 
> Note that the VDPAU driver also relies on memory semantics, i.e., it
> may use DC ZVA (zero cacheline) instructions which are not permitted
> on device mappings. This is probably just glibc's memset() being
> invoked, but I remember hitting this on another PCIe-impaired arm64
> system with Synopsys PCIe IP

DC ZVA can be disabled with the SCTRL_EL1.DZE bit, so that neither kernel 
nor userspace will use it. If the mapping didn't support unaligned writes, 
it would be worse.

Mikulas