On Wed, Jan 20, 2021 at 3:20 AM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > On Tue, 5 Jan 2021 at 17:23, Alex Deucher <alexdeucher@xxxxxxxxx> wrote: > > > > On Tue, Jan 5, 2021 at 8:05 AM Will Deacon <will@xxxxxxxxxx> wrote: > > > > > > On Mon, Jan 04, 2021 at 11:27:24AM -0500, Alex Deucher wrote: > > > > On Tue, Dec 29, 2020 at 8:17 AM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > > > > > > > > > On Wed, 16 Dec 2020 at 23:26, Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > > > > > > > > > > > On Wed, 16 Dec 2020 at 19:00, Alex Deucher <alexdeucher@xxxxxxxxx> wrote: > > > > > > > > > > > > > > On Mon, Dec 14, 2020 at 12:53 PM Ard Biesheuvel <ardb@xxxxxxxxxx> 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> > > > > > > > > > > > > > > Can rebase this on Linus' master branch? There were a number of new > > > > > > > asics added which copy pasted the ARM64 support. > > > > > > > > > > > > > > > > > > > Not sure what you are asking me here. Reverting commit c38d444e44badc5 > > > > > > on top of mainline is not going to fix the other code that was added. > > > > > > Or are you asking me to go and find the patches (how many?) that added > > > > > > new ASICs and fix them for arm64? > > > > > > > > > > > > Note that this code is critically broken, as it may corrupt user > > > > > > process state arbitrarily. So if new code was added that contains the > > > > > > same bug, it should be reverted so that the respective authors can fix > > > > > > it and resubmit. > > > > > > > > > > > > > > > > Is this simply about dropping the newly added references to > > > > > $(dml_rcflags) from the Makefile? Because that is quite trivial ... > > > > > > > > Yes, I was thinking something like the attached patch. > > > > > > > > Alex > > > > > > > From fbc93ca7d7739861ce63f6b483cf23d7cf1d69fb Mon Sep 17 00:00:00 2001 > > > > From: Alex Deucher <alexander.deucher@xxxxxxx> > > > > Date: Mon, 4 Jan 2021 11:24:20 -0500 > > > > Subject: [PATCH] drm/amdgpu/display: drop DCN support for aarch64 > > > > > > > > From Ard: > > > > > > > > "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." > > > > > > > > Disable support until the code can be properly refactored to support this > > > > properly on aarch64. > > > > > > > > Reported-by: Ard Biesheuvel <ardb@xxxxxxxxxx> > > > > Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx> > > > > --- > > > > drivers/gpu/drm/amd/display/Kconfig | 2 +- > > > > drivers/gpu/drm/amd/display/dc/calcs/Makefile | 4 ---- > > > > .../gpu/drm/amd/display/dc/clk_mgr/Makefile | 21 ------------------- > > > > drivers/gpu/drm/amd/display/dc/dcn10/Makefile | 7 ------- > > > > .../drm/amd/display/dc/dcn10/dcn10_resource.c | 7 ------- > > > > drivers/gpu/drm/amd/display/dc/dcn20/Makefile | 4 ---- > > > > drivers/gpu/drm/amd/display/dc/dcn21/Makefile | 4 ---- > > > > drivers/gpu/drm/amd/display/dc/dcn30/Makefile | 5 ----- > > > > .../gpu/drm/amd/display/dc/dcn301/Makefile | 4 ---- > > > > .../gpu/drm/amd/display/dc/dcn302/Makefile | 4 ---- > > > > drivers/gpu/drm/amd/display/dc/dml/Makefile | 4 ---- > > > > drivers/gpu/drm/amd/display/dc/dsc/Makefile | 4 ---- > > > > drivers/gpu/drm/amd/display/dc/os_types.h | 4 ---- > > > > 13 files changed, 1 insertion(+), 73 deletions(-) > > > > > > Acked-by: Will Deacon <will@xxxxxxxxxx> > > > > Applied. Thanks! > > > > It appears your version of the revert does not apply cleanly to v5.10, > so now we're stuck with this broken AArch64 support in a LTS kernel. > > Any objections to taking my original revert into v5.10 as a special backport? No concerns, please go ahead. Acked-by: Alex Deucher <alexander.deucher@xxxxxxx> if you want to send it to stable. Alex _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
