On Mon, Dec 14, 2020 at 06:52:25PM +0100, Ard Biesheuvel wrote: > This reverts commit c38d444e44badc557cf29fdfdfb823604890ccfa. > > Simply disabling -mgeneral-regs-only left and right is risky, given that > the standard AArch64 ABI permits the use of FP/SIMD registers anywhere, > and GCC is known to use SIMD registers for spilling, and may invent > other uses of the FP/SIMD register file that have nothing to do with the > floating point code in question. Note that putting kernel_neon_begin() > and kernel_neon_end() around the code that does use FP is not sufficient > here, the problem is in all the other code that may be emitted with > references to SIMD registers in it. > > So the only way to do this properly is to put all floating point code in > a separate compilation unit, and only compile that unit with > -mgeneral-regs-only. But perhaps the use of floating point here is > something that should be reconsidered entirely. > > Cc: Catalin Marinas <catalin.marinas@xxxxxxx> > Cc: Will Deacon <will@xxxxxxxxxx> > Cc: Dave Martin <dave.martin@xxxxxxx> > Cc: Rob Herring <robh@xxxxxxxxxx> > Cc: Leo Li <sunpeng.li@xxxxxxx> > Cc: Alex Deucher <alexander.deucher@xxxxxxx> > Cc: "Christian König" <christian.koenig@xxxxxxx> > Cc: David Airlie <airlied@xxxxxxxx> > Cc: Daniel Vetter <daniel@xxxxxxxx> > Cc: Daniel Kolesa <daniel@xxxxxxxxxxxxx> > Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> > --- > drivers/gpu/drm/amd/display/Kconfig | 2 +- > drivers/gpu/drm/amd/display/dc/calcs/Makefile | 7 -- > drivers/gpu/drm/amd/display/dc/clk_mgr/Makefile | 7 -- > drivers/gpu/drm/amd/display/dc/dcn10/Makefile | 7 -- > drivers/gpu/drm/amd/display/dc/dcn10/dcn10_resource.c | 81 ++++++++------------ > drivers/gpu/drm/amd/display/dc/dcn20/Makefile | 4 - > drivers/gpu/drm/amd/display/dc/dcn21/Makefile | 4 - > drivers/gpu/drm/amd/display/dc/dml/Makefile | 13 ---- > drivers/gpu/drm/amd/display/dc/dsc/Makefile | 5 -- > drivers/gpu/drm/amd/display/dc/os_types.h | 4 - > 10 files changed, 32 insertions(+), 102 deletions(-) I didn't notice we'd enabled this for arm64, but I agree with the reasoning in the commit message, so: Acked-by: Will Deacon <will@xxxxxxxxxx> The long and short of it is that it is not safe to compile kernel C code without -mgeneral-regs-only on arm64. Will _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
